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  • 101
    Electronic Resource
    Electronic Resource
    Electrical resistivity behavior of mold-cast metal-filled polymer composites (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1109-1114 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Mold-cast, metal-filled composites made of poly(methyl methacrylate) and aluminum or nickel exhibited electrical resistance qualitative behavior as predicted by the percolation and tunneling mechanisms. A precipitous change in resistivity of about 104 ohm-cm was found at volume concentrations of filler in the range of 18.5 to 19.8 vol%. Details of the electrode system are given for making these measurements. Using different polymers does not change the resistance behaviour of the composite to any great degree, suggesting that particle features of shape, size, arrangement, and so forth are the more important parameters. Such particle morphological details are indicated in the included photomicrographs.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341403
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  • 102
    Electronic Resource
    Electronic Resource
    Shrinkage modeling of polyester shrink film (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1121-1128 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A model was developed to quantify the thermal shrinkage behavior of polyester shrink film under isothermal and nonisothermal conditions. This model employs the straightforward first order reaction kinetics to an otherwise microscopically complex relaxation process. It offers three unique parameters for quality control and material specification of shrink film. In the isothermal condition, the induction time, the shrink constant, and the ultimate shrinkage are the three parameters used by the model to quantify the shrinkage of shrink film under an elevated but constant temperature. In the nonisothermal condition, the shrink film is heated using a constant heating rate. Three parameters, which are the onset shrink temperature, the shrink constant, and the ultimate shrinkage, characterize the shrinkage of shrink film. The model fits the experimental data very well. The thermal shrinkage of several polyester homopolymers, copolymers, and polyester blends was investigated and compared to that of poly(vinly chloride) (PVC) shrink film. Two polyester blends containing glycol modified poly(ethylene terephthalate) (PETG) copolyester behave similar to PVC in shrinkage behavior. The effect of stretch temperature, stretch ratio, and stretch rate on the shrinkage characteristics of oriented PETG film was also studied. The stretch temperature has the highest influence on the shrinkage behavior of oriented film.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341405
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  • 103
    Electronic Resource
    Electronic Resource
    Generation of microcellular polymeric foams using supercritical carbon dioxide. I: Effect of pressure and temperature on nucleation (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1137-1147 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Supercritical carbon dioxide is known to swell and plasticize poly(methyl methacrylate), PMMA, dramatically. We have employed a pressure quench in a CO2-swollen PMMA sample to generate a microcellular core structure encased by a nonporous skin. Further, we have demonstrated that classical nucleation theory can be used to model the effects of saturation pressure, temperature, and time on the cell density of the porous materials, provided that the effects of the CO2-diluent on the surface tension of PMMA are adequately taken into account. This is because our system is in a homogeneous liquid state at our operating conditions because of the plasticization. Both model predictions and data indicate that cell density rises sharply at a saturation pressure of approximately 14 MPa (at 40°C), leveling out above 27 MPa. By contrast, the effect of temperature on cell density in the range 40°C to 80°C is minimal.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341407
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  • 104
    Electronic Resource
    Electronic Resource
    Melt crystallization kinetics of syndiotactic polystryrene (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1157-1160 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The crystallization kinetics of syndiotactic polystyrene (SPS) were studied using nonisothermal DSC analysis. Crystallization rates and half-times were determined from the glass transition temperature (∼ 100°C) up to the melt temperature (∼ 270°C) for various molecular weight SPS polymers. The results suggest that the crystallization rate of SPS is molecular weight dependent. These results are also compared with previously determined crystallization kinetics of high density polyethylene. The maximum crystallization rate of high density polyethylene is approximately ten times greater than that of SPS.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341409
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  • 105
    Electronic Resource
    Electronic Resource
    Relating blow moldability to large amplitude oscillatory shear behavior (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 888-893 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The large amplitude oscillatory shear test has been used to discriminate subtle differences in nonlinear viscoelasticity between two high density polyethyene blow molding resins with different processability. Structural network theory was used to explain the subtle differences in terms of entanglement kinetics with remarkable accuracy. The resin with better shape retention characteristics in programmed parison blow molding was found to have a higher kinetic rate constant for molecular re-entanglement.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341104
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  • 106
    Electronic Resource
    Electronic Resource
    Mechanical properties and morphology of liquid crystalline copolyester-amide and amorphous polyamide blends (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 847-856 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of an amorphous polyamide (PA) and a liquid crystalline copolyesteramide (LCP), poly(naphthoate-aminophenoterephthalate) were prepared in a twin-screw extruder. Specimens for mechanical testing were prepared by injection molding. Morphological, thermal, mechanical, and rheological properties were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffractometry, capillary rheometry, and a tensile tester, respectively. The tensile mechanical behavior of the LCP/PA blends was found to be affected by their compositions and specimen thickness. Tensile testing revealed that the tensile mechanical behavior of the LCP/PA blends was very similar to that of polymeric composite and the tensile strength of the LCP/PA (50/50) blend was approximately two times of the value of PA homopolymer and exceeded that of pure LCP. The morphology of the LCP/PA blends was also found to be affected by their compositions. SEM studies revealed that the liquid crystalline polymer (LCP) formed finely dispersed spherical domains in the PA matrix and the inclusions were deformed into fibrils from the spherical droplets with increasing LCP content. It has been found that droplet and fiber formations lead to low and high strength material, respectively. In particular, at specific LCP content (50 wt%), the tensile strength of the LCP/PA blend exceeded that of pure LCP. The improvement in tensile properties is likely due to the reinforcement of the PA matrix by the fibrous LCP phase as observed by SEM. A distinct shell-core morphology was found to develop in the injection molded samples of these blends. This is believed to have a synergistic effect on the tensile properties of the LCP/PA blends. The rheological behavior of the LCP/PA blends was found to be very different from that of the parent polymers and significant viscosity reductions were observed for the LCP/PA (50/50) blend. Based upon DSC, these blends have shown to be incompatible in the entire range of concentrations.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341010
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  • 107
    Electronic Resource
    Electronic Resource
    Construction of fast-response heating elements for injection molding applications (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 894-897 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new type of heating element was developed capable of changing the mold surface temperature by about 70 K in 0.2 s, thus enabling reduction of frozen-in orientation and stresses in injection molded products without undue increase in cycle time. The heater, which consists of two insulation layers with a resistance layer in between, is discussed in this paper. The thickness of this insulation layer proves to be the most important design parameter. Too thick an insulation layer increases the cooling time too much, whereas with a thin layer the surface temperatures will stay too low. Temperature measurements at the heater surface and in the mold wall are reported and demonstrate the extreme fast response characteristics.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341105
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  • 108
    Electronic Resource
    Electronic Resource
    Anisotropy in injection-molded ethylene-propylene-diene rubbers. Part I (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 905-912 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Anisotropy and molecular orientation are well-known phenomena in the field of thermoplastics. In the case of rubber materials only a few studies have described anisotropy. Injection molding has been shown to give rise to higher anisotropy than compression molding. The anisotropy in the rubber material is assumed to be due to molecular orientation and is strengthened by carbon black. In order to understand the mechanism of anisotropy in rubber materials, an extensive study has been performed. In this paper, results from two injection-molded ethylene-propylene-diene (EPDM) rubbers, compounded both with and without carbon black, are presented. The polymers had different molecular weight distributions and the compounds were injected into center-gated 1- and 4-mm-thick disks. The properties measured in different directions were mechanical, dynamic mechanical, and swelling. These measurements show that anisotropy can be a very important factor to take into account. The origin of anisotropy is presumably the molecular orientation which arises during the filling of the mold with the rubber melt.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341107
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  • 109
    Electronic Resource
    Electronic Resource
    Rheokinetic studies for the reaction injection molding of polydicyclopentadiene (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 921-928 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dicyclopentadiene (DCPD) based liquid engineered resins are emerging among the newest commercial reaction injection molding (RIM) systems. Since the filling stage is coupled with chemical reaction, an understanding of the chemorheological changes is critical for establishing moldability criteria. An adiabatic reactive viscometry technique which involves the simultaneous measurement of viscosity and temperature changes was used to investigate the chemorheological changes during the adiabatic copolymerization of a DCPD based RIM system. The influence of impingement mixing conditions and initial material temperature on the reaction kinetics, rheology, as well as the resulting final physical properties of the system were investigated. The “apparent gel time” under adiabatic conditions is estimated from the intersection of the tangents to the initial and final portions of the viscosity curve. An autocatalytic kinetic model with an Arrhenius rate constant was used to model the reaction kinetics.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341109
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  • 110
    Electronic Resource
    Electronic Resource
    The influence of surface heating on the birefringence distribution in injection molded partsPart of this paper was presented at the ATPS 3 Conference in Gargnano (Italy), May 31-June 5, 1992. (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 898-904 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In order to reduce the frozen-in orientation, which is usually present in injection molded products, the effect of high-performance mold surface heaters was investigated. The heaters are capable of changing their surface temperature by 70°C within a few tenths of a second typically, which minimizes their effect on the cooling time. The effects of the heating time, the instant of heating, and the heating power on the birefringence distribution of a polystyrene resin were studied. Reductions of the birefringence peak by a factor 4 to 7 were observed. The birefringence is removed most effectively by heating briefly before and during the injection stage. A heating pulse of about one second and with a power density of 20 W/cm2 then seems to be sufficient. A minimum power density of 10 W/cm2 is needed for the relaxation to occur in this specific system.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341106
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  • 111
    Electronic Resource
    Electronic Resource
    Surface energy changes produced by ultraviolet-ozone irradiation of poly(methyl methacrylate), polycarbonate, and polytetrafluoroethylene (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1233-1238 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Contact angles of water and methylene iodide were measured as a function of UV/O3 treatment time for three polymers: poly(methyl methacrylate) (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE). Surface roughnesses were also measured. Surface free energies were then calculated using relationships developed by Kaelble and Neumann. The surface energy of polycarbonate was found to increase (∼ 60%) during UV/O3 treatment. However, calculations on PMMA were hampered by the formation of a water soluble surface product. On PTFE surfaces, the UV/O3 treatment etched the surface, causing large increases in surface roughness, rendering contact angle measurements impossible. It is concluded that care must be taken in interpreting contact angle measurements and surface energy calculations on UV/O3 treated polymer surfaces.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341602
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  • 112
    Electronic Resource
    Electronic Resource
    Processing effects on poly(ethylene terephthalate) from bottle scrapsPresented in part at PPS European Regional Meeting, Prague, Czechoslovakia, September 1992. (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1219-1223 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Processing of virgin and recycled poly(ethylene terephthalate) (PET) in a twin screw extruder evidences the degradative effect caused by thermal decomposition of poly(vinyl chloride) (PVC) and other impurities, e.g. adhesives, at the processing temperature. Lower melt viscosity and molecular weight, along with higher carboxylic end group concentration, were observed for recycled PET, the extent depending on PET purity. In an attempt to investigate the correlation between the kinetics of degradation phenomena and the level of thermomechanical stress, a novel dynamic method of evaluating thermal stability in processing conditions was developed. Such a method allows the achievement of long equivalent residence times while using lab-scale extruders. As a result of these experiments, PVC-rich recycled PET was shown to reach very low melt viscosity after less than 10 min in processing conditions, while virgin PET retained high viscosity even after 30 min.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341508
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  • 113
    Electronic Resource
    Electronic Resource
    Reaction-induced phase separation during the formation of a polyurethane-unsaturated polyester interpenetrating polymer network (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1239-1249 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this study, an interpenetrating polymer network (IPN) based on a polyurethane (PU) and a partially end-capped unsaturated polyester (UPE) was prepared. The reaction-induced phase separation process of the IPN was studied using a phase contrast optical microscope and a transmission electron microscope (TEM), while reaction kinetics and onset of gelation were determined by a differential scanning calorimeter and a rheometer respectively. Except at low temperatures, the phase separation patterns were found to follow the spinodal decomposition mechanism. An interconnected phase developed quickly and was followed by coalescence of the periodic phase to form droplet/matrix type of morphology. A second level of phase separation also occurred within both the droplet and the matrix phases in some cases. The domain sizes resulting from both levels of phase separation gradually increased until the structure was locked by chemical gelation. Reaction temperature, PU reaction rate, and UPE reaction rate all had significant effects on the final morphology of the formed IPNs.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341603
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  • 114
    Electronic Resource
    Electronic Resource
    Parameter estimation for analysis of vapor diffusion in polymers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1250-1253 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents a general method for estimation of diffusion coefficient and other relevant parameters for the analysis of vapor diffusion in polymers. Sorption curves generated by the constants estimated using the parameter estimation method presented here are in closer agreement with experimental curves than curves generated by other conventional methods.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341604
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  • 115
    Electronic Resource
    Electronic Resource
    Crystallinities of poly(chlorotrifluoroethylene) and its copolymers by differential scanning calorimetry, X-ray diffraction, and density measurements (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1254-1259 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Crystallinities of films of copolymers of chlorotrifluoroethylene with 0 to 4% vinylidene fluoride, different molecular weights and thermal histories were calculated from differential scanning calorimetry (DSC), X-ray diffraction (XRD), and density measurements. The crystallinities for these films range between 16 to 58%, 11 to 71%, and 13 to 77% as determined by DSC, XRD, and density, respectively. Although the numerical value of the DSC, XRD, and density crystallinities obtained by each of the techniques are different, they correlate well with each other. The primary source of error in DSC is the uncertainty in drawing the baseline for separating the heat of fusion and heat of crystallization. In XRD, the ambiguities in the separation of the amorphous and crystalline peaks reduce the precision of the results. Calculation of crystallinity from density values requires that the distribution of the VF2 between the amorphous and crystalline regions be known. In addition, the density technique is not sensitive to variations in the crystalline and amorphous densities.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341605
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  • 116
    Electronic Resource
    Electronic Resource
    Thermal behavior of hydrostatically extruded polycarbonate and high-impact polystyrene (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1269-1274 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Effects of hydrostatic extrusion on the thermal properties of polycarbonate (PC) and of high-impact polystyrene (HIPS) were studied using differential scanning calorimeter (DSC) measurements. A glass transition temperature (Tg) and a peak temperature were determined from the DSC curves for both PC and HIPS extrudates. The Tg values of the PC extrudates, with a percentage reduction in area, R, from 40 to 50%, change appreciably from the value for the as-received PC. The results of the hydrostatic extrusion of the PC billets suggest that a two stage deformation process of molecular chains may be involved. Shear-banding is observed for HIPS extrudates with R = 30 to 60%; this fact indicates that a sub-glass transition (β-transition) occurs at temperatures below Tg. It is suggested that the molecular chains of the HIPS extrudate with R = 70% are oriented in the direction of hydrostatic extrusion. The deformation mechanism of molecular chains caused by the hydrostatic extrusion is discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341607
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  • 117
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    Curing of acrylated epoxy resin based on bisphenol-S (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1297-1303 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The acrylated diglycidyl ether of bisphenol-S was prepared by reacting diglycidyl ether of bisphenol-S (DGEBS) with acrylic acid using dimethyl benzylamine as a catalyst. The acrylated epoxy resin thus obtained was characterized by IR, 13C-NMR, and DSC. The curing reaction of the acrylated epoxy resin with dicumyl peroxide was investigated by differential scanning calorimetry at three different heating rates. The overall curing kinetics were found to be approximately second order, independent of the scan rate. The TGA was used to investigate the thermal decomposition of acrylated epoxy resin and to determine the kinetic parameters such as activation energy, preexponential factor, and reaction order. Such information can be used for quick estimation of polymer lifetimes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341610
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  • 118
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    The compatibility of linear low density polyethylene-polypropylene blends: Viscosity ratio plots (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1260-1268 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of linear low density polyethylene (LLDPE) and polypropylene (PP) show diverse mechanical property behavior in the published literature. The main objectives of this work were: to investigate the effect of viscosity of the component phases on the mechanical properties of such blends and to use the results to obtain a method for compatibilizing diaper manufacturing waste. The significant result of the study was that although LLDPE/PP blends are often termed “incompatible,” when viscosity of the components was more closely matched to each other, increases of as much as 50% in tensile strength and modulus were observed over the “rule of mixtures” line. Also, scanning electron microscopy then showed a more diffuse interface between the component phases. Three dimensional views of plots of viscosity ratio of the blend components as a function of temperature and shear rate were used to demonstrate the closer matching of viscosities for the blend components of the higher performing blends. In processing diaper manufacturing waste, addition of a high molecular weight PP in a manufacturing scale single screw extruder, to provide a closer match of viscosities of the blend components, significantly improved mechanical properties.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341606
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  • 119
    Electronic Resource
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    Coupling agent and glass fibers in polyester mortar (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1287-1296 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study investigates the influence of aggregates, glass fibers and a coupling agent on the compressive and flexural (three-point and four-point bending) behavior of a polyester mortar. Particle size of fine aggregates (quartz and limestone) varied from 0.1 to 5 mm (0.004 to 0.2 inch) and the glass fiber content was varied up to 6% by weight of mortar. A silane was introduced into the polyester mortar by pretreating the aggregates and the glass fibers. The mechanical properties of mortar were studied at room temperature. The test results indicate that the selection of aggregate type, size and distribution is very important. Silane treated aggregate systems showed more than 66% increase in compressive strength and 35% increase in flexural strength when compared to the untreated systems. Addition of glass fibers enhances the strength and toughness of the polyester mortar, and silane treatment of glass fibers helps to further enhance these properties. Flexural (three-point bending)-to-compressive strength ratio varied from 0.28 to 0.35 for unreinforced system and from 0.26 to 0.54 for the reinforced system. The mortar with only 14% polyester and 86% aggregates (by weight) and a coupling agent had a compressive strength of 103 MPa (15,000 psi) which is 94% of the polyester polymer strength. A stress-strain relationship is proposed to represent the complete stress-strain response under compression and flexural loading. Also, a method is proposed to quantify the failure patterns.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341609
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341701
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    An extension of the Painter-Coleman miscibility guide to ternary polymer blends (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1314-1318 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The idea of separating the free energy of mixing into two contributions (corresponding to the “physical” or “nonspecific” and to the “specific” interactions, respectively) proposed by Painter and Coleman has been extended to ternary polymer/polymer/polymer blends. In this paper experimental phase diagrams of three ternary blends have been reproduced by estimating both contributions for the interaction energy density (Bij) which characterizes each polymer pair. In contrast to the Painter-Coleman Miscibility Guide rules, we have found that, in some cases, “specific” contributions positive and unfavorable to the mixing, due to the self-association of one of the components, can describe more adequately the experimental trends.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760341703
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    Fiberoptic intrinsic fluorescence for in-situ cure monitoring of amine cured epoxy and composites (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1025-1032 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The cure reactions of epoxy-diamine and its composites are monitored in-situ using the intrinsic fluorescence of the aromatic diamine, diaminodiphenyl sulfone (DDS). With a fiberoptic fluorimeter, in-situ cure monitoring was performed via a single fiber, distal-end probe, in neat epoxy as well as in commercial grade prepregs containing graphite fibers and DDS curing agent. The prepregs were investigated during multiply lamination in an oven. The fluorescence excitation spectra were obtained by emitting at 420 nm with a scan range of 320 to 400 nm, and the DDS peak position was determined as a function of cure time and temperature. The DDS spectra show a progressive red shift up to 24 nm when the primary amine is reacted with epoxide to become the secondary and the tertiary amines. The spectral shift of the DDS is also correlated with the extent of epoxide reaction determined by the Fourier transform infrared (FTIR) spectroscopy. Both data exhibit a linear relation, consistent with the behavior of the DDS peak shift, which increases linearly with the amine reaction. The excitation spectra also show a temperature dependency such that the amount of red shift increases with the measurement temperature in a manner that can be described by an exponential function. The temperature effects also depend on the state of cure in the sample. The temperature correction can be made by the application of an empirically developed equation. Thus, a direct comparison can be made among the on-line data obtained under varying conditions of cure, by reducing the spectral data to any reference temperature. This intrinsic fluorescence technique is much simpler than the previously reported extrinsic fluorophore technique, which requires the addition of an extrinsic fluorophore and an internal dye, and can be applied to any commercial prepregs containing DDS, thus making it a very powerful and widely applicable monitoring tool for composite processing.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760341212
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341301
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    Numerical nonisothermal flow analysis of non-Newtonian fluid in a nonintermeshing counter-rotating twin screw extruder (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1033-1046 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A simulation technique for nonisothermal flow analysis of non-Newtonian fluid in a nonintermeshing counter-rotating twin screw extruder was developed by modifying the flow analysis network (FAN) method. The local shear viscosity in the flow field was calculated by an iteration method combing the three types of mean shear rate functions. The modified Cross model and an Arrhenius-type function for temperature dependence were also introduced. Streamlines in the flow field are represented by computing the movements of fluid particles based on the flux fields. The computed residence time from the streamlines led us to solve the energy equation by replacing the coordinate system. The profiles of pressure, shear rate, shear viscosity, temperature, and residence time were simulated. The influence of operating and geometrical parameters on the screw characteristics are discussed. Further, residence time distribution (RTD), strain distribution function (SDF), and interfacial area growth are predicted from the computation of streamlines to analyze the mixing capabilities of the extruder.
    Additional Material: 23 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760341302
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    Extrudate roughness of high-density polyethylene and linear low-density polyethylene: Determination of key parameters using screening design (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1047-1055 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A screening design is used to establish the contribution of various parameters to the roughness of cylindrical extrudates. A dimensionless response variable is proposed to characterize the extrudate roughness, and the effects of ten parameters on this roughness response were examined. Two polyethylenes (one high density and one linear low density) were investigated using a 45 mm single screw extruder. The results show that the main parameters affecting the extrudate roughness are, in order of importance, apparent shear stress at the die wall, die diameter, ratio of die length to diameter, and type of polymer. The other six parameters (the use of an additive, recycling, type of entrance adapter, die material, die temperature, melt temperature) were found to have a non-significant contribution to roughness.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760341303
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    Molecular dynamics of polybenzimidazole and contributions from chaosThis topic was previously presented at the 1992 U.S. Army Edgewood Research, Development and Engineering Center, Scientific Conference on Chemical Defense Research, November 17-20, 1992, Aberdeen Proving Ground, Md. (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1070-1079 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Molecular dynamics has been used to study possible dynamic mechanisms that may contribute to the property degradation known to exist for polybenzimidazole (PBI) upon hydration. During this study, chaotic movements of a chain pair were observed. Changes in onset and duration of this movement were also observed, which depended upon both hydration state and stress direction involved. Such trends suggested that specific mechanistic pathways may exist that could directly lead to property (such as modulus) loss.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760341306
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    Rheological properties of blends of lithium- or sodium-sulfonated polystyrene ionomers with polyamide 6 (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1056-1064 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dynamic viscoelastic properties of blends of alkali metal salts of sulfonated polystyrene ionomers with polyamide 6 were investigated in the melt. The blends of lithium-sulfonated polystyrene (10 mol% sulfonation) with polyamide 6 (LiSPS/PA-6) behaved as a homogeneous viscoelastic fluid over most of the blend composition range, since blending with PA-6 disrupted the ionic network of the LiSPS. Specific interactions between the lithium sulfonate group and the amide group are believed to be responsible for the behavior. By contrast, blends of sodium-sulfonated polystyrene with PA-6 (NaSPS/PA-6) showed typical behavior of immiscible systems in that they exhibited large positive deviations from the log-additivity rule for complex viscosity. This implied that sodium sulfonate groups did not interact strongly with amide groups, in contrast to the behavior of lithium sulfonates. Oldroyd's emulsion model was applied to the results of dynamic viscoelasticity studies of both the immiscible ionomer/PA-6 blends and the polystyrene/PA-6 blends. For the latter, the fit was much better than for the former. This difference in behavior might be due to partial miscibility or to the presence of an indistinct phase boundary in the “immiscible” ionomer-based systems.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760341304
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    On the pressure dependency of the viscosity of molten polymers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1535-1546 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A slit viscometer to measure the viscosity of polymer melts under processing conditions is described. Along the slit a pressure drop is generated by applying a pressure at both the entrance and the exit. In this way the pressure in the center can be controlled independently of the shear rate. The pressure gradient in the slit is measured by means of three pressure transducers which are mounted in the region of fully developed flow. Results of pressure-dependent viscosity measurements on polystyrene, polyacrylonitrile-butadiene-styrene, and polypropylene are presented in a shear rate range of five decades. The flow curves obtained at different pressures and temperatures can be shifted onto a master curve. The shear thinning behavior of the three materials is adequately described with the generalized Cross-Carreau equation, while the zero shear viscosity is modeled with a generalized Arrhenius-W.L.F. relationship, incorporating a pressure dependency. Alternatively, it is possible to describe the zero shear viscosity in terms of the free volume fraction and the temperature.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342004
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    Laser welding of polymers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1547-1549 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Deep penetration welding and cutting of metals can be carried out at high speed with relatively low laser power. The efficient coupling of the laser radiation to the metal is due to the formation of a “keyhole.” Over the years, an attempt has been made to transfer the results on metals to plastics. It will be shown here that keyhole welding of plastics is limited to the very restricted set of plastics that have a boiling point. Volume heating, a mechanism that is not applicable to metals, is restricted to plastics with a good transparency for the incident radiation and with a high optical quality. Finally, surface heating is shown to be the most common mechanism for heating plastics.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342005
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    About the existence of a percolation threshold in solid solution of N-isopropylcarbazole/polycarbonate mixtures (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1560-1563 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Direct current (DC) dark conductivity, (σ) measurements have been carried out in thin films of N-isopropylcarbazole/polycarbonate mixtures (NIPC/PC) for relative weight ratio (x) in the range 2 to 80% by weight of NIPC in PC at room temperature. The experimental results suggest a non-percolative transport in the concentration range explored. In the range 20 to 80%, a hopping character and power law dependence σ ∼ (x - xc)3 is found with xc = 0.16. In the range 2 to 20% these relations are masked by the influence of hops involving polymer matrix which makes such a system not a suitable model for testing percolation ideas.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342007
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    Design of electrofusion joints and evaluation of fusion strength using fusion simulation technology (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1529-1534 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fusion simulation is one of the key techniques in designing and producing electrofusion (EF) joints for gas distribution and in evaluating fusion joint integrity. This paper describes the result of a numerical simulation of a thermal fusion process, using the finite element method. A nonlinear heat transfer computer program was used to obtain the temperature profile of a large electrofusion joint at fusion. The effects of applied voltage, heating time, wire pitch, and ambient temperature were examined for designing a 150-mm EF joint. A method to shorten the cooling time was also investigated. The fusion condition range suitable for a 150-mm EF joint was found to be slightly narrower than that suitable for a 50-mm EF joint. Examination of the effect of wire pitch revealed that if the pitch is extremely large, thermal degradation starts in the resin close to the wire before the fusion-interface strength reaches the maximum value. We have developed a program to simulate the process of closing the gap between the pipe and the joint due to resin expansion and melting after the power is supplied.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342003
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    The behavior of bubbles in Bueche model fluids (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1550-1559 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The nonlinear oscillation of a spherical gas bubble in polymer solutions was theoretically analyzed. Using the rheological equation of Bueche model fluid, the equation of motion and the pressure equation for a bubble are derived. According to the numerical calculations, the effects of rheological properties and initial radius of the bubble on the bubble radius-time history, pressure at the bubble wall, critical and equilibrium radii of the bubble, as well as pressure distribution in liquid are discussed.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342006
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760342101
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    Enhancement of electrical conductivity of uniaxially and biaxially processed poly(p-phenylene sulfide) films (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1564-1579 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A fundamental study of electrical conductivity of uniaxially and biaxially stretched poly-p-phenylene sulfide (PPS) film was conducted. In this paper, we paid special attention to understand the effect of processing conditions on the electrical conductivity as well as the conduction mechanism of tantalum pentafluoride (TaF5) doped PPS. The electrical conductivity of PPS film was measured by a four-point probe method in the parallel and perpendicular directions to the stretching direction. The infrared spectra of doped and undoped stretched PPS films demonstrate that the TaF5 doping causes distortion (polaron) in PPS chain and conduction. A similar discussion was reported by Tsukamoto, et al. (1, 2). They found the delocalization of π-electrons in doped PPS by X-ray spectoscopy (XPS), infrared spectroscopy (IR), and C13-NMR. The conductivity of doped PPS films increased with increasing stretching ratio. The crystallinity effect on the electrical conductivity was investigated by changing crystallinity of PPS films in terms of annealing and multi-axially stretching. Orientation development was investigated by wide angle X-ray scattering and birefringence techniques. The relationship between conductivity and orientation of stretched PPS films was investigated by introducing electrical anisotropy.
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    URL: http://dx.doi.org/10.1002/pen.760342008
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    Rubber modified epoxy resin. II: Phase separation behavior (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1598-1604 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: DGEBA (diglycidyl ether of bisphenol A)-ATBN (amine terminated butadiene acrylonitrile copolymer) blends exhibited upper critical solution temperature (UCST) behavior. Triethylene tetramine (TETA) was introduced as an amine curing agent of epoxy. The real-time phase separation behavior of ATBN-added epoxy system during cure was investigated using laser light scattering. SEM (scanning electron microscopy) and optical microscopy were also employed to observe the morphology of the epoxy blends. Since the DGEBA-ATBN blends showed UCST behavior, the degree of phase separation when cured at low temperature was higher than that when cured at high temperature. The domain correlation length increased as the curing temperature was lowered. Dynamic mechanical analysis (DMA) results indicated that the phase inversion occurred above 20 wt% of ATBN composition.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342104
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    Rheology and physical properties of ternary blends containing a thermotropic liquid crystalline copolyester (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1605-1612 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ternary blends of polyarylate (PAR) U-Polymer 100, thermotropic liquid crystalline copolyester (LCP) Vectra A950, and a block copolyesterether Hytrel 7246 were investigated in terms of rheological properties, morphology, and mechanical properties. The PAR/Hytrel blend exhibited melting point depression and gave a unique single Tg over the entire range of blend compositions. Addition of Hytrel to the PAR/LCP blend decreased both dynamic viscosity and storage modulus over the normal processing temperature range. Further, it notably reduced the voids between the LCP domains and the matrix, and improved the mechanical properties. The optimum usage level of Hytrel proved to be 2 phr.
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    Molecular and lamellar structure of an extrusion-grade medium-density polyethylene for gas distribution (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1581-1588 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An extrusion-grade medium-density polyethylene was fractionated by size exclusion chromatography and selective solvent extraction. The fractions were studied by infrared spectroscopy, differential scanning calorimetry, and transmission electron microscopy. Infrared spectroscopy showed that chain branching was concentrated to the low molar mass material. Transmission electron microscopy showed the presence of roof-shaped crystals in the low molar mass samples and curved S-or C-shaped lamellae in the high molar mass samples. These features could be used for identification of different molar mass species in the unfractionated sample.
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    URL: http://dx.doi.org/10.1002/pen.760342102
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    A polarized light scattering approach for dispersed phase morphology characterization in simulated polymer blends (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1589-1597 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A light scattering technique using a normal-incidence polarized light beam for the characterization of skin/core simulated polymer blend samples is described. The patterns of reflected, polarized scattered light from an inhomogeneous blend were captured using a video camera. The blend was illuminated from a focused laser source. The simulated samples were constructed by incorporating glass fibers (skin) and glass microspheres (core) in a polymer matrix. Asymmetrical patterns were obtained. They reflect the anisotropic nature of the near-surface morphology. Moreover, the change of the anisotropy ratio of the iso-intensity curves plotted, as a function of distance from the position of the incident laser beam on the sample, gives information about the skin and the core content as well as the skin thickness.
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    URL: http://dx.doi.org/10.1002/pen.760342103
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    Polymeric antiplasticization of polycarbonate with polycaprolactone (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1613-1618 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Physical blends of polycarbonate (PC) with polycarprolactone (PCL), containing 0 to 30% PCL were prepared by melt mixing. The compatible blends were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), mechanical testing, rheological and density measurements. Yield strength, elastic modulus, and density of the blends were found to attain maximum values, depending on PCL content, while Tg continuously decreased. PCL presence resulted in the embrittlement of PC as detected by impact and tensile tests. These combined data lead to propose a mechanism of polymeric antiplasticization in the PC/PCL system; a phenomenon uncommon in polymer-polymer blends. Simultaneously, the PC's β-transition intensity was depressed, as detected by DMA. Activation energy of PC secondary relaxation process was found to be higher for PC/PCL blends than for PC. Thus, local, intermolecularly non-cooperative motions, usually associated with β-relaxation, are restricted in the presence of PCL. The addition of PCL to PC results in increased shear sensitivity and lower high shear rates viscosity, improving processability.
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    URL: http://dx.doi.org/10.1002/pen.760342106
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    Analytical approximation of degradation profiles in polymer products (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1619-1627 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A general, but simple, analytical technique is proposed for the solution of diffusion-controlled reaction problems (as, for example, occur during the photooxidation of polymers). With this technique the stationary concentration and reaction rate profiles can be calculated for arbitrary reaction kinetics and concentration dependent diffusion coefficients. As an example, the photo-oxidation of polyolefins is considered, which involves complex, concentration dependent, reaction kinetics. Excellent agreement between the analytical approximation and the numerical solution is obtained. Further, an analytical expression for the degradation profile (extend of reaction) is derived, which includes the starting-up effect. It is shown that owing to instationary effects, the degradation profiles obtained with artificial weathering tests may differ considerably from those obtained with outdoor weathering experiments. It is therefore suggested that artificial weathering tests be used to measure the reaction rate parameter and calculate the degradation profile rather than measuring the degradation profile directly.
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    URL: http://dx.doi.org/10.1002/pen.760342107
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760342201
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    Quantitative model relating electrical resistance, strain, and time for carbon black loaded silicone rubber (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1628-1634 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A quantitative model has been developed relating electrical resistance with strain and time for carbon black filled silicone rubber compounds. The model is based on concepts and methods used in the field of viscoelasticity. Relaxation experiments are performed in order to evaluate material parameters. With these, resistance-strain-history relations, under other loading conditions may be predicted.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342108
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    Effect of moisture absorption on the tensile properties of short glass fiber reinforced poly(butylene terephthalate) (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1645-1655 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Injection molded short glass fiber reinforced poly(butylene terephthalate) was subjected to hygrothermal aging at two different relative humidities - 81.2% and 100% RH. A single free phase model of diffusion has been used to analyze the data obtained from the kinetics of moisture absorption study. The diffusion coefficient and the equilibrium moisture content were found to be dependent on the volume fraction of fibers and relative humidity. Incorporation of short glass fibers into a poly(butylene terephthalate) matrix has led to a significant improvement in the retention and recoverability of the tensile properties. Examination of fracture surfaces using a scanning electron microscope (SEM) has revealed some evidence for the hydrolysis of the polymer matrix. The hydrolysis resulted in the formation of microvoids, the absence of a plastic deformation process, and degradation at the fiber-matrix interface.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342202
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    Bisphenol-A bimodal epoxy resins. Part I: The dynamic mechanical characterization of a 6300 (340/22,500) weight average molecular weight system (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1635-1642 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: By using an advanced epoxy resin of 22,500 weight average molecular weight two bimodal systems of 6300 weight average molecular weights were prepared. By altering the curing procedure normally used to cure epoxy resins and high molecular weight resins we have succeeded in minimizing the difficulty associated with preparing bimodal epoxy resin systems. The ultimate Tg of these bimodal systems is associated with the phase morphology and controlled by the curing conditions employed. For the completely phase separated bimodal system a Tg of 473 K is reported and for the partially phase separated system a Tg of 466 K is reported. Equations were developed for predicting the equilibrium shear modulus of these bimodal systems. Theoretical predictions based on these equations were found to be consistent with experimental results.
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    URL: http://dx.doi.org/10.1002/pen.760342109
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    Poly(ethyene terephthalate)-solvent interaction: Gelation and melting point depressionA portion of this work was presented at the Symposium on Recent Advances in Fiber and Polymer Science, March 7-9, 1990, held at N.C. State, Raleigh, N.C. (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1656-1663 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The interactions between poly(ethylene terephthalate) (PET) and six high temperature solvents are discussed in terms of gelation and melting temperature depression. The six solvents are 1′-acetonaphthone (AN), phenyl ether (PE), biphenyl (BP), 1-methyl naphthalene (MN), nitrobenzene (NB), and a eutectic mixture of phenyl ether and biphenyl (EU). Although the six solvents have very similar solubility parameter values, the dissolution, gelation, and gel melting temperatures of the PET-solvent systems are vastly different. The characteristic transition temperatures (dissolution, gelation, and gel melting temperatures) of the six solvents decrease in the following order: PE 〉 EU 〉 BP 〉 MN 〉 AN 〉 NB, which is the reverse order of the solvent power. While the transition temperatures of the gel vary with the solvent system, the melting temperature of the dry gel formed from quiescent solution is independent of solvent system. That is, PET-solvent interactions are only discernible in solvated state (wet gel). All the experimental results suggest crystallization is the primary cause of gelation of high temperature PET solutions, with crystals acting as junction points in the network. Based on the dissolution and gel melting temperatures, interaction parameters for the six PET-solvent systems have been calculated.
    Additional Material: 7 Ill.
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    Rubber toughening of poly(lactide) by blending and block copolymerization (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1674-1684 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Copolymers of L-lactide with 15 or more mole % D-lactide are amorphous, noncrystallizable hydrolytically degradable materials. These glassy materials are brittle in tension and bending. To make these materials suitable for use as load-bearing devices in biomedical applications, toughness has to be enhanced. This is effectively accomplished by introducing a separate degradable rubber phase in the amorphous matrix. Several approaches have been explored: solution blending and coprecipitation of trimethylene carbonate and ∊-caprolactone rubbers and poly(lactide), preparation of ABA triblock copolymers and blending of ABA block copolymers with the amorphous poly(lactide) matrix. In all cases very tough materials could be prepared. These materials are easily processable by compression molding at relatively low temperatures.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342205
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    Morphology and properties of an epoxy alloy system containing thermoplastics and a reactive rubber (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1664-1673 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel approach for toughening thermosetting epoxy matrices using both thermoplastics and liquid reactive rubbers as modifiers has been investigated. The network structure of the modified epoxy systems was characterized using dynamic mechanical analysis, and the morphology of the multiphase structure was examined using scanning electron microscopy (SEM). To investigate the continuity of the phase domains, the constituents in the phase domains were positively identified using solving etching and RuO4 staining techniques for transmission electron microscopy (TEM). The fracture toughness of the modified and basic epoxy samples was measured using compact tension (CT) specimens. Quite limited toughness improvement was achieved for the epoxy modified with only the PSu thermoplastic, or the liquid rubber by itself. However, the fracture toughness was found to increase dramatically when a proper combination of both the liquid reactive rubber and thermoplastic was simultaneously incorporated into the epoxy. Toughening by using dual modifiers resulted in maximum improvement of fracture toughness with minimal compromises in processability and Tg depression by rubbers.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760342204
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    The heterogeneous nucleation of microcellular foams assisted by the survival of microvoids in polymers containing low glass transition particles. Part II: Experimental results and discussion (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1698-1706 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The experimental data obtained for the nucleation of microcellular foams are compared with the theoretical model developed in the first part of this paper. Polystyrene (PS) with rubber particles as nucleation sites is used as an exploratory system. Nitrogen is used as a physical blowing agent to nucleate the bubbles. The influence of process variables, such as saturation pressure, foaming temperature, and concentration and size of rubber particles, is discussed. Results indicate that all these variables play important roles during the nucleation process. A nucleation mechanism based on the survival of microvoids against the resisting surface and elastic forces has been modeled to obtain the cell nucleation density. Increase in saturation pressure increase the cell density to a critical pressure. Beyond this critical pressure, there is no increase in bubble number, indicating that all microvoids are activated. The effect of temperature is more complex than the effect of pressure. Increase in concentration of the rubber particles increase the nucleation cell density. In general, the experimental data are well described by the nucleation model presented in Part I.
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    URL: http://dx.doi.org/10.1002/pen.760342207
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    The heterogeneous nucleation of microcellular foams assisted by the survival of microvoids in polymers containing low glass transition particles. Part I: Mathematical modeling and numerical simulation (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1685-1697 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The existing models based on classical nucleation theory are not able to explain satisfactorily the nucleation phenomenon of microcellular foams in thermoplastics. Here, we extend the analysis of Kweeder (24), who developed a new model that considers the presence of microvoids, resulting from the thermal processing history of the polymer, as potential nucleation sites. The nucleation model “concentrates” on the stresses and thus void formations in the rubber particles. Since these are pre-existing microvoids, bubble nucleation depends on the survival of these voids to grow rather than the formation of a new phase as modeled by classical nucleation theory. The population of viable microvoids with a sufficiently large radius to survive and overcome surface and elastic forces has been modeled to yield the cell density. A log-normal distribution, which relates to the rubber particle size, has been used to model the distribution of microvoids in the polymer composite material. The model depends on various process parameters such as saturation pressure, foaming temperature, concentration of nucleating agents, solubility of the blowing agent in the polymer, and the modulus. High impact polystyrene (HIPS) was added to polystyrene to obtain polymers with different concentrations of rubber gel particles, the nucleating agent, and used here for this study.
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760342301
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    Reactive extrusion of acrylic acid grafted polypropylene with hexadecylamine (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1750-1757 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: To study the possibility of the production of branched polypropylene (PP) by a reactive extrusion (REX) route, side chains were introduced on the backbone of a polypropylene material by reacting hexadecylamine with acrylic acid grafted PP. Experiments were carried out both in solution and in the melt, and the products were analyzed by FTIR, elemental analysis, dynamic mechanical, and rheological techniques. Analysis of the FTIR spectra of the samples produced in the solution reactions, at an equal molar ratio of [ -NH2]/[-COOH] without catalyst addition and without removal of the by-product, revealed that the formation of imide was increased with increasing the reaction time up to 10 h, while a further increase in reaction time resulted in a reversal of the reaction. In the REX experiments, FTIR analysis showed that the imide formation increased with the [-NH2]/[-COOH] molar ratio. At a molar ratio of one, more imide was present in the REX product than the in-solution one. Elemental analysis suggested that the nitrogen content in the products initially increased with [-NH2]/[-COOH] molar ratio and then reached an almost constant value at molar ratio values of about unity. The glass transition temperature (Tg) was measured by dynamic mechanical analysis (DMA), and it was found that the attachment of the alkyl chains caused a reduction in Tg of the products. Finally, rheological measurements showed that the shear viscosity of the products increased with the amine/carboxyl molar ratio at low shear rates and that their moduli were enhanced as a result of the attachment of the alkyl side chains.
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    URL: http://dx.doi.org/10.1002/pen.760342306
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    In-line monitoring of molten polymers: Near infrared spectroscopy, robust probes, and rapid data analysis (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1758-1766 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The concept of improved product quality and reduced costs has revolutionized analytical techniques in the polymer industry. It has brought in-line analysis to the forefront, with near infrared (NIR) spectroscopy proving to be a very viable technique for such operations. A system for continuous in-line near infrared monitoring of molten polymer blends, copolymers, and polymer reactions is being developed. The ultimate objective is to use this monitoring system to develop feedback control for polymeric processes. Experiments on blends of polystyrene and poly(phenylene oxide) have been performed by using a flow cell, located at the exit port of a single-screw extruder. Qualitative analysis of spectral data has been substantiated by a variety of quantitative (multivariate) techniques. Robust calibration models, suitable for on-line predictions, have been developed. The success of in-line process analysis depends on the performance of fiber-optic probes that are inserted into the process stream. These probes normally succumb to the demands of the rigorous process environment, typical of polymeric processes, i.e., high temperatures, high pressures, and adverse chemical conditions. Design and development of fiber-optic probes that are capable of withstanding such harsh conditions have also been undertaken. Results will be reported on the polymeric systems and optical probes.
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    Long-term properties of hot-water polyolefin pipes - a review (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1773-1787 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This is a review on the long-term behavior of polyolefin pipes used in hot-water environments. Included in the review is work done on pipes of crosslinked polyethylene, isotactic poly(butene-1), isotactic polypropylene and medium-density polyethylene, and in particular the extensive work performed at Studsvik, Sweden. A collective view of the changes in antioxidant concentration profiles and molecular/physical structure accompanying hot-water exposure is presented. Failure at high stress levels is preceded by gross deformation (Stage I failure), whereas at lower stresses fracture is brittle either without any signs of thermal oxidation (Stage II) or induced by a strong and spatially concentrated thermal oxidation (Stage III). It is shown that the Stage III lifetime can be divided into three phases, denoted Regimes A, B, and C. They involve internal precipitation of antioxidant from a supersaturated solution (Regime A), diffusion-controlled migration of antioxidant to the surrounding media (Regime B), and degradation of the polymer by thermal oxidation (Regime C). For hitherto reported cases the Regime B life constitutes 80% to 90% of the entire life. A presentation is also made of current lifetime extrapolation methods.
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    URL: http://dx.doi.org/10.1002/pen.760342402
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    On the significance of the standardized notched impact strength for materials selection and design (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1799-1807 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Experimental data on the standard Charpy notched impact strength (CNIS) for a large sampling of particulate-filled and rubber-modified polypropylenes were analyzed. To determine the significance of the CNIS for material selection and design, CNIS data were compared with fracture toughness measurements expressed as the critical strain energy release rate G′c, measured under impact loading. A scale factor representing the state of stress at the crack tip was calculated, assuming small scale yielding, Class I linear elastic fracture mechanics (LEFM). Based on the data, three principal groups of materials were identified. In the smallest of the three, CNIS and G′c measurements showed the same functional dependence on the material variables studied and were characterized by a scale factor independent of the composition. In these cases, one can justify comparisons of toughness of different compositions using single values of the CNIS, since the materials are probably being compared in equivalent states of stress. In a second group, CNIS and G′c also show the same functional dependence on material variables, but exhibit large variations in the scale factor with composition. One should not compare the toughness of different materials from this group based on single values of CNIS, since it is likely that the comparisons would not be made relative to equivalent states of stress. In these cases, only measurements of G′c can separate the effect of specimen geometry from those of the intrinsic properties of the material. The majority of materials studied fell into a third group, in which the CNIS and G′c exhibited substantially different functional dependencies on the material properties, and the scale factors depended also on composition. In these latter cases, a comparison of CNIS values for different compositions is not a reliable indication of the relative toughness and is of little value as a parameter for material selection and design.
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    URL: http://dx.doi.org/10.1002/pen.760342404
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760342401
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    In-line monitoring of titanium dioxide content in poly(ethylene terephthalate) extrusion (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1767-1772 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Peak absorbance changes correlated to changes in species concentration have been the norm in applied spectroscopy, while baseline shifts have been more of an inconvenience. Taking the first or second derivative of the spectra eliminates these baseline shifts. However, with multivariate techniques becoming more readily available, repeatable baseline changes may now be monitored and correlated to specific physical changes. This concept has been studied by monitoring the concentration of titanium dioxide (TiO2), a white inorganic filler, in molten poly(ethylene terepthalate) (PET). Various mixtures of filled and unfilled PET resins were run through a single-screw extruder, and near infrared spectra were collected in-line by using a flow cell, housing two fiber-optic probes, and mounted downstream of the extruder. The presence of titanium dioxide caused the scattering of light that resulted in a systematic baseline shift. The baseline shifts were correlated to the TiO2 concentration data. Multivariate techniques involving the use of singular value decomposition (SVD) to perform partial least squares regression (PLS) were applied to quantitatively determine TiO2 content in the PET melt stream. Standard error of prediction (SEP) values of about 1% were obtained for a model based on two factors.
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    A viscoelastic micor-mechanical analysis for dimensional stability of a composite layer (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1815-1822 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Coefficient of thermal expansion mismatch between the epoxy layer and composite substrate of “inner layers” can lead to large residual stresses during the manufacture of printed wiring boards (PWB). The viscoelastic nature of the polymeric resin (epoxy) leads to a relaxation of the stresses and a resulting change in dimensions of the inner layer over long periods of time. Here, we treat a micro-mechanical model using linear viscoelasticity in a finite element thermal stress analysis to demonstrate the time dependency of the ply dimensions upon cooling from near the glass transition temperature (Tg) of the resin to room temperature. The inner layer shrinkage reaches its highest value when room temperature is reached, but the part will continue to change dimensions (shrinkage recovery) for a long time as the in-plane residual stresses relax from their peak values. This evolution takes place over many decades of time. The results show that the long term behavior of dimensional changes is especially pronounced when the effects of time-temperature superposition (TTS) are included below Tg.
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    Interfacial tension in polymer melts. I: An improved pendant drop apparatus (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1823-1833 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An apparatus is described to measure interfacial tension for molten polymer pairs. The apparatus is based on the pendant drop method. A CCD color video camera captures the image of a pendant drop profile, which is analyzed on-line using a microcomputer. These almost continuous measurements permit the detection of possible changes in the behavior of the melt that might affect the interfacial tension through thermal degradation. A special syringe to inject the pendant drop has been designed in order to avoid problems such as the capillary effect of the tube of the syringe and the necking and detachment of the pendant drop. The accuracy of the apparatus was verified using water/n-hexane and water/n-octane. Experimental results for polypropylene/polystyrene (PP/PS) are presented. The interfacial tension between the polymer pair decreases as temperature increases and as molecular weight decreases. Interfacial tension is estimated from the drop shape when the drop is at mechanical equilibrium. For polymer systems, mechanical equilibrium normally takes from 1 to 10 h to occur. However, transient values of interfacial tension (apparent interfacial tension values obtained before mechanical equilibrium is reached) may be used to estimate the interfacial tension at equilibrium by extrapolation, thus reducing the required experimental time.
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    Deformation and entanglement in semicrystalline polymers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 318-329 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Transmission electron microscopy and optical studies of thin films of isotactic polystyrene (iPS) and polyoxymethylene (POM) provide evidence for a distinction between crazing mechanisms in semicrystalline polymers above and below Tg. In the latter temperature regime, deformation in iPS and POM crystallized at high supercooling has been discussed in terms of existing models for crazing in amorphous glassy polymers, based on entanglement ideas. Above Tg, where the difference in mechanical behavior of the amorphous and crystalline regions becomes marked, the fibrillar nature of local deformation appears to be a consequence of the inhomogeneity of the undeformed polymer.
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    URL: http://dx.doi.org/10.1002/pen.760340414
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    The influence of inclusion geometry on the elastic properties of discontinuous fiber composites (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 352-360 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Simplifying assumptions are used to reduce micromechanical treatments to compact expressions which directly reveal the role of the inclusion shape and aspect ratio in establishing the elastic behavior of heterogeneous materials. Attention is directed to the comparison of aligned ellipsoidal and cylindrical inclusions that exhibit transversely isotropic behavior characterized by five independent elastic constants. These comparisons show that the effective transverse in-plane moduli (ET*, k* and GTT*) are essentially independent of inclusion shape for aspect ratio greater than ∼ 20; ellipsoidal inclusions provide higher longitudinal reinforcement than cylindrical inclusions of equivalent aspect ratio. Comparison of predictions with measured elastic moduli shows that both the cylindrical and ellipsoidal shape models for isolated inclusions overpredict longitudinal elastic constants for systems which exhibit evidence of inclusion agglomeration. The notion of an effective aspect ratio based on clusters of filaments responding as a coherent unit appears to provide a means for reconciling a wide range of experimental observations.
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    URL: http://dx.doi.org/10.1002/pen.760340417
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    Properties of electropolymerized polycarboxyphenylmethacrylamide matrices/graphite fiber composites: Crosslinking effect (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 341-351 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Imide formation from -CONH and -COOH functional groups of 2-carboxyphenylmethacrylamide (2-CPM), 4-carboxyphenylmethacrylamide (4-CPM), 4-carboxyphenyl methacrylamide/methylmethacrylate (4-CPM/MMA) and 4-carboxyphenylmethacrylamide/N-phenylmalemide (4-CPM/NPMI) electropolymerized matrices was investigated. It was found that 2-CPM polymers undergo intramolecular imidization and anhydride formation, which result in a small amount of crosslinked network. On the other hand, the thermally cured 4-CPM polymer demonstrates a significant increase in gel fraction. Tg and dynamic storage modulus, owing to crosslinked network formation. Tgs of 4-CPM/MMA and 4-CPM/NPMI composites measured by thermomechanical analysis after thermal heating were increased and were correlated very well with the preheating time. The 4-CPM/MMA composites with a particle crosslinking (Tg increased to 245°C) maintained a higher Izod impact strength than a typical epoxy composite (200 kJ/m2 vs. 100 kJ/m2). Upon heating to promote crosslinking, a lower shear strength (65 MPa) of a 4-CPM/MMA composite increased to a strength of 78 MPa, close to the 80 MPa of an epoxy composite at 67% fiber volume fraction. A lower water absorption of around 1% was associated with the increased crosslinking. The mechanical properties of the 4-CPM/NPMI composites showed a similar trend upon preheating.
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    URL: http://dx.doi.org/10.1002/pen.760340416
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    Diffusion of low molecular weight substances into a fiber with skin-core structure - rigorous solution of the diffusion in a coaxial cylinder of multiple components (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 330-340 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The diffusion equation of low molecular weight substances (penetrant) into a coaxial cylinder of multiple components (m) was formulated in general and solved rigorously. As the simplest but a practical case of m = 2, which corresponds to the diffusion of penetrant into fibrous material with skin and core structure, the diffusion of penetrant was analyzed in detail. That is, changes in the penetrant concentration distribution within the coaxial dual cylinder of skin and core components and the total amount of penetrant sorbed within the cylinder both with time after exposing the cylinder to atmosphere of fixed penetrant concentration of Cout were calculated with variation of the diffusion coefficient ratio (D1/D2) and the radius ratio (R2/R1), where D1 and D2 are the diffusion coefficients of penetrant in the core and the skin, and R2 and R1 are the radii of the fibrous material and the core, respectively. Keeping (R2/R1) at a constant value of 1.2 but varying (D1/D2) from 104 to 10-2, the penetrant concentration distribution was calculated and found to be much different particularly within the core between (D1/D2) 〉 1 and (D1/D2) 〈 1. The sorption curves were also found to deviate in their respective ways from that of Fickian curve of a homogeneous cylinder with (D1/D2) = 1 except at initial stage of sorption. Further, by keeping (D1/D2) constant but varying (R2/R1) from 1.1 to 1.5, the effects of relative skin thickness upon the sorption curve were studied.
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    URL: http://dx.doi.org/10.1002/pen.760340415
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    Orientation parameters for the specification of effective properties of heterogeneous materials (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 361-370 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A general formulation is presented for the orientation averaging of the properties of representative volume elements of heterogeneous materials. Approximations are introduced that result in the identification of four independent orientation parameters that are required to specify a general state of three-dimensional orientation. The general relationships are reduced further for the special case of “planar” and “axial” distribution and applied to an aggregate averaging scheme for short-fiber composites.
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    URL: http://dx.doi.org/10.1002/pen.760340418
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    A computer-aided analysis of automatic degating molds for injection molding of plastic balls (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 238-248 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A computer software has been developed to speed up the design process of automatic degating molds used for injection molding of plastic balls. Following an introduction to the ball making process and the associated mold design consideration, the algorithm and formulation of the software are presented. To demonstrate its versatility, the software developed is adopted to design both testing and production molds that best meet the design and production requirements. Two testing molds were built. While one was used to verify the gate size predicted, the other was built to confirm the workability of the automatic degating design. The results of testing runs have also been used to finalize the details for designing the production mold. The software developed is compact enough to be run on an IBM/PC compatible and has the capability to communicate with commercial CAD/CAM systems to provide necessary drawings or CNC files for mold fabrication.
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    URL: http://dx.doi.org/10.1002/pen.760340310
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    Paul H. Lindenmeyer: Scientist and manager of science (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 249-250 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340402
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    A review on the tensile strength of polyethylene fibers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 266-268 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340406
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    Crack propagation in biaxially oriented polypropylene at low temperature (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 269-278 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The crack growth behavior of polypropylene biaxially oriented by cross-rolling was studied at low temperature. Single edge notch testing produced a stable tearing type of crack growth in both 50% and 80% biaxially oriented polypropylene at -40°C, in contrast to the brittle fracture of unoriented polypropylene. The crack growth in the two oriented materials began slowly and accelerated to a constant rate that was higher in the 80% oriented material than in the 50% oriented material. The main difference between the crack growth behavior of the two was the longer period of initial slow growth in the case of 80% orientation. This period of slow growth corresponded to crack growth through the notch tip damage zone. Residual strength diagrams were used to present the crack growth data obtained when the stress state was intermediate between plane stress and plane strain. Fractography revealed large differences among the fracture surfaces of the three materials with the unoriented polypropylene showing a grainy appearance from the brittle fracture. The two oriented materials showed considerable ductility. The 50% oriented material showed many voids in the fracture surface, indicating that voiding during the fracture process contributed significantly to the toughness improvement. The 80% oriented polypropylene showed delamination crazing on the fracture surface with layered material and fibrils bridging the crazes.
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    The oxidative degradation of imide polymers. I: Ozonolysis of a model compound, N-phenylphthalimide (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 279-284 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The reactions of N-phenylphthalimide films with ozone have been studied under a variety of conditions: dry ozone, moist ozone, ozone plus ultraviolet light, as well as ozone plus water vapor plus ultraviolet light. This compound is a conveniently available model for imide polymers. These reaction conditions represent simulation of certain aspects of the space environment. For each set of reaction conditions the reaction products were determined by combined gas chromatography/mass spectrometry. Semiempirical molecular orbital computations were made of the relative energetics of possible reaction pathways consistent with the generation of the observed products. The reaction products found indicate fragmentation of the imidic moiety for which the energetics are favorable.
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    Polypropylene composites. III: Chemical modification of the interphase and its influence on the properties of PP/mica composites (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 485-492 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A surface treatment technology was developed for PP/mica composites that produces a diffuse interlayer with excellent adhesion between the components. The interlayer is created by the silane treatment of the filler and the chemical modification of the polymer components, and its polarity gradually decreases from the surface of the filler to the matrix. Properties of the composites depend on the characteristics of the interphase. With changing chemical composition, the characteristics of the interphase change from a thin, rigid layer to a more diffuse, elastic one. Properties of the composites change accordingly, optimum properties are achieved with a thick interlayer ensuring good stress transfer, strength, hardness, acceptable impact properties, and low mold shrinkage.
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    URL: http://dx.doi.org/10.1002/pen.760340605
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    Start-up pressure transients in a capillary rheometer (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 493-499 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The “rise time” required to achieve a steady pressure reading in a capillary rheometer operated at constant piston speed can be very long, up to several hours under certain circumstances. This phenomenon can pose a serious problem in the measurement of melt viscosity, and it would be useful to be able to estimate the rise time in the planning of experiments. Based on experiments involving several types of polyethylene, we found that the rise time increases with L/D and the amount of polymer initially in the reservoir and decreases with diameter and piston speed. When the rise time is short, melt viscoelasticity contributes to the rise time, but when it is long, melt compressibility is the dominant factor. A model was developed for the latter case, and this was found to give an accurate prediction of the rise time, given the viscosity and compressibility. The model can also be used to determine the power-law parameters from the start-up pressure trace, P(t), for a single experiment. Alternatively, if the viscosity is known, the compressibility can be inferred from a single pressure trace.
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    The effect of lithium chloride on polybenzimidazole and polysulfone blend fibers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 428-433 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polybenzimidazole (PBI) and polysulfone (PS) do not form miscible blends; however, the tensile properties of the polymer blend in fibers, and the fiber process window, are strongly dependent on the presence of LiCl. The addition of LiCl opens the molecular chains and reduces dope viscosity. As a result, LiCl increases the stiffness of PBI/PS fibers while making them brittle. The process window for fabricating useful fibers seems to be narrowed by the presence of LiCl. PBI/PS fibers spun from a dope that does not contain LiCl have a broad process window and their overall fiber performance is superior. LiCl also reduced the degree of sulfonation during the stabilization process.
    Additional Material: 9 Ill.
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    A property trend study of polybenzimidazole using molecular modelingPart of this work has been previously presented at the Navy Second Annual R&D Information Exchange Conference, Naval Weapons Center, China Lake, Calif., April 2-4, 1991, and at the 1991 U.S. Army Chemical Research, Development, and Engineering Center Scientific Conference, Aberdeen Proving Ground, Md., Nov. 19-22, 1991. (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 434-437 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Molecular mechanics and dynamics have become a standard analysis tool used in drug design and synthesis, but it has not generally been used as part of structural and mechanical analysis. The need for such tools is an obvious extension of structure-property correlations known in polymer formulation, engineering, and manufacture. This study probes the use of mechanics and dynamics techniques to help explain property trends found in hydrated polybenzimidazole (PBI).
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    Dynamic mechanical analysis and its relationship to impact transitions (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 420-427 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Detailed, instrumented impact tests were carried out between about - 100 and 60°C for flexible poly(vinyl chloride) (PVC), ethylene vinyl acetate (EVA), and polypropylene (PP) films. Secondary impact transitions in addition to the main transitions were detected for all three films, indicating that multiple impact transitions may be far more general in occurrence than commonly expected. Wide frequency (from 0.05 to 100 Hz) dynamic mechanical spectra of the same materials were also generated over similar temperature ranges. A new data treatment method was proposed whereby the material dissipation function was evaluated by summing the responses over broad frequency ranges of the loss modulus and the impulse spectrum. The dissipation function when plotted as a function of temperature was found to accurately (to within 3 to 5°C) predict the location of the main impact transitions for all three polymers. In addition, the existence and location of the secondary impact transitions for both PVC an PP were predicted. Both the functional form and the temperature match between the experiments and predictions strongly support the validity of the proposed method. However, some discrepancy remained in predicting the very low temperature (-65°C) impact transition for EVA.
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    Photoinitiated crosslinking of low density polyethylene. III: Degradation and stabilization of photocrosslinked polyethyleneThis is Part III of a series of papers on “Photoinitiated Cross-linking of Low Density Polyethylene”. For Part I and II, see Refs. 3 and 4. (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 446-452 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Electron spectroscopy (ESCA) and reflectance infrared spectroscopy (ATR) were used to measure surface oxidation of photocrosslinked polyethylene. The deterioration of bulk properties during an artificial weathering test was also measured. It was found that the UV-irradiation during crosslinking process decreases the stability of the material considerably. Three kinds of antioxidants and photostabilizers (hindered phenols, hindered amines, and organic sulfides) which have no absorption in the UV region of 300 to 400 nm were added before crosslinking to improve the stability of the crosslinked material. Neither the rate nor the degree of photocrosslinking at different depths of the sample were affected significantly by these additives. It was found possible to prevent the decrease in stability due to the photocrosslinking by using small amounts of a stabilizer, e.g. 0.05% Tinuvin 770 (hindered amine).
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    Rheological properties of structured fluids (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 438-445 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetic theory proposed by Soong and Liu for describing the rheological properties of structured fluids has been extended to predict shear-thinning, shear-thickening, thixotropy, and antithixotropy in different ranges of shear rates. Viscoelastic properties, as given by the Gordon-Schowalter Maxwell model, with a non-constant modulus, have also been considered. The theoretical predictions are compared with the predictions of a model used by Ait-Kadi, et al. (1988), for a hydrolyzed polyacrylamide solution containing 20 g/1 of NaCl. the predictions and experimental data for the viscosity and primary normal stress coefficient are in reasonably good agreement. The stress growth functions have also been calculated and have been found to be consistent with experimental observations.
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340601
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    Blends of a thermotropic LCP and a thermoplastic elastomer. II: Formation and stability of LCP fibersThis work has been presented at the European Regional Meeting of the Polymer Processing Society, 15-18 September 1991, Palermo, Italy. (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 453-460 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The formation of fibers during blending of a thermotropic liquid crystalline polymer (LCP) with a thermoplastic elastomer (TPE) using shear flow, and the stability of the fibers and the blend morphologies at elevated temperatures were studied. The polymers used were Vectra A900 (LCP) and Kraton G1650 (TPE). Fiber formation in (predominantly) shear flow was studied using a single screw extruder of which the die was removed. Fibers were obtained in blends with 5 vol% LCP at shear rates as low as 6.3 s-1. Conventional extrusion through a die was used for preparing materials for the studies of the thermal stability of blends and isolated fibers-isolated LCP-fibers surrounded by a TPE-matrix disintegrate when held above the melting point of the LCP. Annealing of the blends at this melting temperature results in changes of the morphology and in a fairly rapid decrease of the modulus of elasticity.
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    Quiescent polymer crystallization: Modelling and measurements (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 461-471 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The problem of predicting nonisothermal crystallization kinetics based on isothermal data is considered, with reference to the difficulties involved, both experimental and theoretical. The kinetic model used is the differential form of the Nakamura equation which is an extension of the Avrami equation so as to apply to nonisothermal crystallization. Nonisothermal induction times are obtained from isothermal induction times according to the concept of induction time index. The theory of Hoffman Lauritzen is used to extrapolate the limited isothermal crystallization rate data. Good agreement between DSC (differential scanning calorimetry) nonisothermal crystallinity results and model predictions is obtained for our own data on poly(ethylene terephthalate) (PET) and some literature data on nylon-6, if the temperature lag between the sample and the DSC furnace is taken into account. The advantages of the present approach in process modeling are pointed out. Quenching experiments have also been performed in which PET slabs are allowed to cool and crystallize from the melt under quiescent conditions. The resulting crystallinity distributions in the thickness direction are measured and predicted by using kinetic parameter values obtained from isothermal DSC measurements alone.
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    Processability and thermal properties of blends of high density polyethylene, poly (ethylene terephthalate), and ethyl vinyl acetate compatibilizer (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 472-476 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Because of differences in chemical structure and rheological characteristics, high density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) are incompatible when blended during recycling of PET soft drink bottles. To improve the properties of the blends, ethylene vinyl acetate copolymer (EVA) was used as a compatibilizer. Based on torque rheometer tests, the higher the concentration of PET in the blends, the higher the initial loading torque. Blends of 50% HDPE and 50% PET had the lowest equilibrium torque. Equilibrium torque was highest at 5% EVA. The presence of EVA made only a slight difference in the glass transition temperatures of HDPE/PET blends. Higher EVA content in the blend resulted in a lower melting endotherm. Thermogravimetric analysis showed that thermal stability was independent of EVA content; but the more PET in the blend, the lower the final weight loss.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340603
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    Spherulitic crystallization: An analysis of inverse stefan problems in cartesian, cylindrical, and spherical coordinate systems (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 477-484 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Spherulitic crystallization presents an inverse Stefan problem, which is solved by numerical methods using the DuFort-Frankel scheme and Lagrangian coordinate systems. The numerical solution shows excellent agreement with the analytical solution in the Cartesian coordinate system. A systematic error in the numerical solution for the spherical and cylindrical coordinate systems is examined by a material balance for the system. The systematic error was found to decrease rapidly as the dimensionless time increased and the grid spacing decreased.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340604
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340901
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    In-line optical monitoring of polymer injection molding (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 671-679 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An optical sensor, consisting of optical fibers to transmit light to and from the mold cavity, was constructed for the purpose of measuring the onset of polymer solidification during injection molding. The sensor was used to detect characteristic fluorescence radiation from a dye which had been doped into the resin at very low concentration. By measuring changes in fluorescence intensity it was possible to detect whether the state of the resin was liquid or solid. We observed that, as the resin cooled in the mold, the onset of solidification was indicated by highly characteristic and distinct changes in the fluorescence intensity/time profile. Application of the method involved the use of a calibration relationship between the fluorescence intensity and temperature of the doped polymer in order to determine the distict features which characterize the onset of solidification. Injection molding of a glass forming polymer (polystyrene) and a crystallizable polymer (polyethylene) was monitored by this technique.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340809
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    Dielectric properties of blends of polycarbonate and acrylonitrile-butadiene-styrene copolymer (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 697-706 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The low frequency dielectric properties of polymeric blends of polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) were studied in the temperature interval of 100 to 170°C. Attention was focused on a 60/40 (m/m) PC/ABS blend. The results were compared with dynamic mechanical measurements in torsion and with the results of a morphological investigation using scanning electron microscopy (SEM). Besides the relaxations at the glass transition temperatures of the components an additional strong low frequency dielectric dispersion was observed, which was not found in mechanical measurements. This low frequency polarization process is due to interfacial polarization at the boundaries between conductive ABS and non-conductive or slightly-conductive PC. It is shown how this process can be described by the dielectric models for two-phase heterogeneous materials. The Looyenga model offers the best description of the detected effects, while the Hanai model is less suitable. The shape factor of the ABS phase as used for modeling the dielectric properties agrees well with the observed morphology using SEM. It is shown for the dielectric measurements on the 75/25, 60/40, and 45/55 (m/m) PC/ABS blends how the connectivity of the ABS phase can be sensitively derived from the eletrical conductivity of the blend, whereas mechanical measurements are highly senstive to the connectivity of the PC phase.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340902
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    Fracture behavior of poly(vinyl chloride)/methyl methacrylate/butadiene/styrene polymer blends (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 680-690 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The fracture mode of poly(vinyl chloride)/methyl methacrylate/butadiene/styrene (PVC/MBS) polymer blends can change from ductile to brittle in accordance with the changes in shape of the test specimen or test conditions. Therefore, the mechanisms of impact energy absorption and the main cause of stress whitening are complicated. The following results on PVC/MBS blends were obtained by carrying out fracture experiments at different test speeds and temperatures: (1)The ductile/brittle fracture mode of the PVC and PVC/MBS blends can be explained by σ (the craze initiation stress)/σy (the shear yield initiation stress), which depends on the strain rates and temperature.(2)The fracture behavior of the PVC/MBS blends can be classified into the following types from the standpoints of fracture mode and whitening degree: Fracture I: ductile fracture without whitening;Fracture II: ductile fracture with whitening; andFracture III: brittle fracture without whitening.(3)The following concepts can be estimated from the measurements of yield stress, specific gravity and SEM, TEM and visual observations. In Fracture I, shear yield occurs mainly. In Fracture II, both shear yield and crazing occur. In Fracture III, deformation of the rubber and local crazing occur.(4)The main cause of stress whitening in PVC/MBS blends is light scattering by cavities in the rubber particles.(5)In Fracture II, at first, crazes with cavities in the rubber particles occur. Then, shear yield occurs. Finally, crazes are healed by the heat, and only the cavities in the rubber remain.
    Additional Material: 19 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340810
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    The large strain compression, tension, and simple shear of polycarbonate (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 716-725 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polymeric materials subjected to large strains undergo an evolution in molecular orientation. The developing orientation and corresponding strengthening are highly dependent on the state of strain. In this paper, we examine and compare the very different stress-strain results of polycarbonate produced from four types of mechanical testing: uniaxial compression, plane strain compression, uniaxial tension, and simple shear. These tests produce different states of orientation within the material and, in the case of simple shear, the principle axes of orientation rotate during the deformation. The ability of the recent constitutive model of Arruda and Boyce (1992) to predict the to predict the observed behavior is evaluated. The model has been incoporated into a finite element code in order to properly simulate the material behavior during the inhomogenous deformations of tension (cold drawing) and simple shear. The material properties of the model are obtained from the uniaxial compression test and the model is then found to be truly predictive of the other states of deformation demonstrating its fully three dimensional capability. The disadvantages of the tensile and simple shear tests for obtaining the data needed to accurately quantify the large strain material behavior of polymers are shown and discussed.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340904
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    Optimization of the structure of integral skin foams for maximal flexural properties (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 726-733 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effective flexural properties of integral skin foams (ISF), are modeled using Euler-Bernouli beam theory along with a power law empirical equation relating the properties of a homogeneous foam to its density. The optimal density profile that maximizes the effective flexural modulus of an ISF beam of fixed overall density, and with the density constrained to lie in a given range, is continuous when the power law exponent (n) is less than 1. For n 〉 1, the optimal density profile is discontinuous with a low density core and a high density skin. The effective flexural modulus of such sandwich beams is maximized for a fixed density ratio (ratio of the core density to the skin density) and fixed overall density. The maximal flexural modulus is found to increase monotonically with decreasing density ratios and increasing values of n. The flexural strength of the sandwich beam is also maximized considering failure to occur by tensile fracture or buckling of the skin. In this case an optimal skin thickness and an optimal density ratio are obtained for a fixed overall density. The results are useful for the design and evaluation of flat ISF panels.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340905
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    In-situ cure monitoring of diamine cured epoxy by fiberoptic fluorimetry using extrinsic reactive fluorophore (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 707-715 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes the application of a molecular sensor for in-situ monitoring of epoxy-diamine cure via remote sensing fiberoptic probes. A custom-built, fiberoptic fluorimeter allows on-line recording of fluorescence spectra directly from the cure environment. Cure reactions in epoxy-diamine network, such as diglycidyl ether of bisphenol A-diaminodiphenyl sulfone (DGEBA-DDS) or diglycidyl ether of butanediol-diaminodiphenyl sulfone (DGEB-DDS), have been monitored by a reactive molecular sensor, diamino azobenzene (DAA). DAA exhibits sensitive changes in UV-visible and fluorescence spectra due to the conversion of its primary amine groups to secondary and tertiary amine groups. Fluorescence intensities are correlated with extent of reaction in epoxy network and processing parameters, such as cure temperatures and time. The use of an internal reference dye for normalization of fluorescence intensities is necessary for the quantitative correlation of spectral signals with the network structure. Variables affecting the fluorescence intensity such as excitation volume, probe location, excitation intensity fluctuation, temperature, and background intensities from optical fiber can be calibrated by normalizing the signal intensities against the internal reference. Sulforhodamine 101 was found to be a satisfactory reference dye which provides stable, readable signals over temperatures up to 200°C.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340903
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    Kinetic parameters estimation for cure reaction of epoxy based vinyl ester resin (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 742-749 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new graphical estimation technique is proposed for the determination of the kinetic parameters describing an autocatalytic reaction. A differential scanning calorimeter was used to monitor the reaction kinetics of an epoxy-based vinyl ester resin. The method utilizes information from a zero initial reaction rate, conversation at vitrification, the ratio of reaction rate constants under different isothermal conditions, and characteristics of the phenomenological kinetic model with assumptions being made about the overall reaction order. By fitting data to the integrated reaction rate equation with adjustments for the isothermal conditions, the kinetic parameters are estimated without using a linear or nonlinear regression method. Different kinetic parameters can be estimated from data before and after the gel point which was obtained from the relationship between the glass transition temperature and the degree of cure.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340907
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    Kinetic model and thermal properties of a thermally cured thermosetting polycarbonate (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 734-741 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Diethylene gycol bis(allyl carbonate) is widely used for the production of optical plastic for lenses, safety glasses and guards, watch crystal, and instrument windows. The monomer polymerizes via a free radical mechanism using benzoyl peroxide as an initiator to form a thermosetting polycarbonate. This polymerization process involves a long cure cycle at temperature below 100°C. Differential scanning calorimetry (DSC) and rheometric dynamic testing are used to characterize the thermal and kinetic properties. These properties include the heat of reaction, activation energy, rate constants of polymerization, and time and extent of cure at gelation.
    Additional Material: 12 Ill.
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    On the rheological behavior of latex polystyrene blends (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 750-758 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The synthesis of latex two-phased polystyrene blends has been accomplished by three different mixing routes: (1) PS-b-XPS system consisting of a physical blend of polystyrene (PS) and crosslinked polystyrene (XPS) lattices, the latter being lightly crosslinked with divinylbenzene (less than 1% DVB), (2) (XPS-s)-PS system obtained by styrene polymerization in presence of a XPS seed latex, and (3) (PS-s)-XPS system, in which styrene and DVB are copolymerized in presence of a PS seed latex. Structuring of these PS/XPS systems resulted in different microstructures by each of the procedures. Different rheological behaviors have been noticed, along with a rather interesting property dependence on XPS content and DVB concentration. The polymerization method appears to be critical to the development of well-characterized, tailor-made latex microstructures, insofar as the order of monomers addition determines much of the polymerizations sites.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340908
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    Spectra composite that withstands torch flame test (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 765-778 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In recent years, the development of high performance Spectra® fibers has received increasing attention in industry. Because of the outstanding capability to absorb energy, these polyethylene fibers are frequently used in damage tolerant composite materials to protect equipment, apparatus, and/or people against blast and debris of explosion or projectiles. Since the fiber is thermally stable, it is possible to design composite structures that are suitable for use in applications where prolonged exposure to flame is anticipated. In this paper, we report the findings obtained in a recent flammability evaluation of a Spectra composite subjected to a torch flame, and to hot metal balls. The Spectra composite structures that will be discussed were found to withstand these exposures without burning and the smoke generation and toxic gas emission were far below the limits set in the standard for current aircraft interior materials.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340910
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    Masthead (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341001
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    Developing critical extrusion parameters for nylon 6, nylon 66, and nylon 46 polyamide from the rheology data (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 759-764 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes a new approach to the rheological characterization of engineering plastics such as nylon 6, 66, and 46 polyamides using a capillary rheometer. The melt viscosity data as a function of temperature, shear rate, and residence time were measured and evaluated to demonstrate how to accurately predict critical extrusion parameters, such as barrel temperature profile, stock temperature window, and the screw design requirements, for extruding strip, tubing, and profiles. The results of this work provide a practical and simple quality control tool to select a polyamide resin for optimum processing, and to develop critical processing parameters for extrusion.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760340909
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    The synthesis and characterization of novel thermotropic liquid crystalline poly(aryl ether ketone)s (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 781-793 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The synthesis and characterization of novel thermotropic liquid crystalline poly(aryl ether ketone)s based on the reaction of a liquid crystalline mesogen containing monomer, biphenol, and a crystal-disrupting substituted monomer, t-butyl- or phenyl-, hydroquinone with 4,4′-difluorobenzophenone are described. Two families of copolymers - a biphenol/t-butylhydroquinone series of 90,75,50, 25, and 0% biphenol, and a biphenol/phenylhydroquinone series of 75, 50, 25, and 0% - are evaluated. Thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 75% biphenol. The first order and second order transitions associated with melting, crystallization, thermotropic liquid crystalline mesophases, and glass transition temperatures (Tgs) of each copolymer are investigated. The thermal transitions are correlated with optical microscopy and X-ray and/or electron diffraction characteristics. It was observed that the Tg increases and end group concentration decreased after isothermal heat treatment indicative of further polymerization. These materials are believed to be the first known thermotropic liquid crystalline poly(aryl ether ketone)s.
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    The effect of preloading on the mechanical properties of polymeric foams (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 794-798 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The polymeric foams investigated with regard to their mechanical properties were the rigid foams polystyrene, polyurethane, and phenolic, and the semirigid foam polyethylene. Preloading of the rigid foams was found to decrease the modulus by an amount that increased as the extent of preloading increased, and to decrease both the modulus and collapse stress in the case of the semirigid ones. The shape of the stress-strain curves of the foams was also significantly changed by the preloading, and a reduction in cushioning properties in static compression was observed.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760341003
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    Polymer blends of polyethersulfone with all aromatic liquid crystalline co-polyester (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1129-1136 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polymer blends of polyethersulfone (PES) with an all aromatic liquid crystalline co-polyester (LCP) were investigated. In addition, PES oligomers with the reactive functions end groups (-ONa) were added as a third component to the above blends in order to improve their properties. Flexural properties, such as modulus and strength, and dynamic viscoelastic properties, such as dynamic storage elasticity (E′) and loss tangent (tan δ), of the blends were measured. The morphology of blends was characterized using a differential scanning calorimeter (DSC) and a scanning electron microscope (SEM). Of the flexural properties, the modulus of PES increased almost linearly with increasing LCP content. However, strength decreased as LCP content increased to 20 wt%. In contrast, the addition of the PES oligomers had little effect on modulus, but strength was clearly improved. Regarding dynamic viscoelastic properties, the oligomer-containing blends exhibited complex behavior. Regarding morphologies, SEM analysis revealed that the LCP was not fibrous in the core of the blend containing 40 wt% or less, but the addition of the PES oligomers made LCP fibrous even in blends with low LCP content. It was concluded that the PES oligomers with reactive functional groups acted as a compatibilizer in polymer blends of PES/LCP.
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    URL: http://dx.doi.org/10.1002/pen.760341406
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    Flow induced phase inversion agglomeration: Fundamentals and batch processing (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 865-880 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel agglomeration technique, based on flow induced phase inversion (FIPI) is described and applied to the batch preparation of polyethylene-bound abrasive calcite agglomerates. Water soluble polymers are used to agglomerate the needle-like crystals of tetraacetylethylene diamine and also sodium chloride crystals. In a typical isothermal FIPI agglomeration process primary particles are dispersed in the molten binder, which is subsequently inverted by the addition of sufficient amount of primary particles, which also defines the critical filler concentration at phase inversion, Cc. Agglomerate particle size is primarily a function of Cp - Cc where Cp is the mean concentration of filler. Cc decreases with increasing binder molecular weight and primary particle surface area. Agglomerate size distribution is affected by processing, mainly by the mixing time after phase inversion. For the non-isothermal FIPI agglomeration process, phase inversion is induced locally, by the addition of fine particles in the molten binder. Phase inversion is then propagated by cooling the dispersion during mixing. Agglomerate characteristics such as particle size, particle size distribution, binder concentration distribution in each agglomerate size range, agglomerate topology, binder morphology in the agglomerates, agglomerate strength, and agglomerate dissolution rate in water were evaluated. These agglomerate characteristics are related to the binder and filler properties as well as to the processing conditions.
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    URL: http://dx.doi.org/10.1002/pen.760341102
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    A nonlinear dynamic model of a servo-pump controlled injection molding machine (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 881-887 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents the development of a nonlinear mathematical model and a microcomputer controlled servo-pump system for the study of the dynamics of a servo-pump controlled injection molding machine (IMM). The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics in the nozzle. The comparison between the simulation results and experimental investigations indicated that the nonlinear dynamic model is a reasonable representation of a servo-pump controlled IMM. The output flow rate and working pressure of a servo-pump controlled IMM can be reasonably represented by the nonlinear model when the acrylonitrile-butadiene-styrene (ABS) is injected.
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    URL: http://dx.doi.org/10.1002/pen.760341103
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    Electronic Resource
    Deformation and energy absorption of polymer foams as a function of 2-D indenter and absorber geometries (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 857-864 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two-dimensional indenters (flat plate and cylinder) were used to compress rectangular and trapezoidal foam energy absorbers as a function of polymer, foam density, and thickness. An increased deformation volume formed when the indenter contact area was less than the foam absorber area, resulting in both increased energy absorption and stress transmitted to the indenter (i.e., “load spreading”). The deformation volume was trapezoidal, not prismatic, and was characterized by the indenter geometry, dimensions, and foam thickness. Conservative energy absorber design can be achieved by using “energy absorption diagrams” that account for the indenter (i.e., product) and absorber geometry and degree of load spreading.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341011
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    Electronic Resource
    Electronic Resource
    Design and processing optimization of extruder screws (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 937-945 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Only recently has increasing use been made of computer simulation in the field of extruder engineering. This simulation is based on physico-mathematical process models. In order to achieve a closed, process engineering-based extruder layout and operating behavior simulation it is necessary to have models describing the throughput behavior, the melting process, the temperature development, the pressure profile over the screw length, the residence time distribution, the mixing and dispersion processes, and also the torque and power requirements. In the Plastics Technology Section of the University of Paderborn (KTP) a program for the computer-aided design of extruders (REX), financed by 17 companies, was developed which will permit rapid application of the models developed there and will fulfill the requirements set out above. Since no computation-intensive numerical methods like Finite Element or Finite Difference Methods (FEM, FDM) are required, the algorithms are very rapid, which means that short computing times are achieved (just a few seconds on an IBM AT).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341111
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