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  • Chemical Engineering  (3,294)
  • 2020-2022
  • 1990-1994  (3,294)
  • 1950-1954
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  • 1
    Electronic Resource
    Electronic Resource
    Direct patterning using metallo-organics and its application to mask repair (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1605-1609 
    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: Au patterns are formed by photographical patterning of polymeric Au mercaptoterpenes (Au resinate), followed by bakeout of the Au resinate patterns to remove carbonaceous materials. Since commercially available Au resinate is not sensitive to 436 nm (g-line) light and cannot be photographically patterned, we mixed azide (photocrosslinker) with Au resinate to give photosensitivity to the g-line. The mixture of Au resinate and azide was spun on an Si substrate, and then exposed with 436 nm (g-line) light by a standard contact printing technique. Upon exposure, Au resinate was crosslinked by the reaction with azide, and became insoluble. Au resinate patterns were generated by development with monochlorobenzene. On baking out the Au resinate patterns to remove carbonaceous materials, we obtained 2 μm line and space Au patterns. The conductivity of the Au patterns obtained was 1/4 that of bulk Au. For a mask repair application, we mixed Cr resinate with a mixture of Au resinate and azide to improve the adhesion of the resulting metal patterns onto the quartz plate. The transmittance and the adhesion were found to depend on the bakeout condition and the mixing ratios of the Cr resinate. Bakeout in vacuum with 0.1 torr oxygen gave far better adhesion and opaqueness than bakeout in air, because of residual carbon in the resultant metal. Mask repair was carried out at the optimized condition by using a spot exposure system. The clear defect was repaired with the transmittance 〈 1% and good adhesion.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322111
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  • 2
    Electronic Resource
    Electronic Resource
    Novel auto-photosensitive polyimides with tailored properties (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1623-1629 
    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 overview is given on auto-photosensitive polyimides as introduced for the first time in 1985. It is shown how development proceeded and how the chemical basis of auto-photosensitive polyimides was extended beyond BTDA. Novel “photosensitizer tetracarboxylic dianhydrides” like 2,3,6,7-thioxanthonetetracarboxylic dianhydride (TXDA) were synthesized and copolymerized into preimidized nonphotoactive polyimides containing tetracarboxylic acids like 6FDA or ODPA. Novel photosensitive polyimides were obtained that carry all essential features of BTDA based systems plus higher photospeed. They provide the ability to better tailor material properties to specific applications.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322115
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  • 3
    Electronic Resource
    Electronic Resource
    Rubber-toughening of glass fiber-epoxy filament wound composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1057-1063 
    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 attempt was made to improve the properties of filament wound glass fiber-epoxy composites by addition of carboxyl-terminated-butadiene-acrylonitrile (CTBN)-rubber to the matrix. The interlaminar GIc of unidirectional glass fiber-epoxy increased significantly with CTBN addition whereas the flexural strength decreased. The weepage stress in hoop loading of ±50 degree angle-ply pipes was higher for unmodified as compared with 10 phr CTBN-modified epoxy matrix pipes. However, the strain at weepage and the stress and strain at nonlinearity were higher for the pipes based on toughened epoxy. The reason for the lower weepage stress is that, although the toughened matrix pipes show higher resistance to cracking, their stiffness is lower. The addition of small amounts of CTBN-rubber (about 5 percent by weight is suggested) to the present epoxy matrix for filament winding can be done with only a minor increase in viscosity. This is a way of toughness enhancement for applications where the matrix stiffness reduction and increased moisture absorption are of minor importance.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311410
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  • 4
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    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.760311501
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  • 5
    Electronic Resource
    Electronic Resource
    Orientation of precrystallized poly(ethylene terephthalate) (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1071-1078 
    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 orientation characteristics of crystalline poly(ethylene terephthalate), PET, were studied as a function of degree of crystallinity, orientation temperature, and stretch ratio. Oriented samples were analyzed with respect to mechanical, shrinkage, and barrier properties. The results show that (a) significant impact property improvement can be achieved by orienting crystallized PET, (b) the modulus, ultimate strength, and yield stress increase with orientation of precrystallized PET, (c) the initial degree of crystallinity can affect the strain-hardening properties of PET, and (d) the total amounts of shrinkage and shrinkage stress of stretched PET increase with increasing amounts of crystallinity before orientation.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311412
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  • 6
    Electronic Resource
    Electronic Resource
    The permeability and compressibility of aligned and cross-plied carbon fiber beds during processing of composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1064-1070 
    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 of the most important input parameters needed to simulate the processing of continuous fiber laminated composites are the fiber bed permeability and the portion of the autoclave load borne by the consolidating fiber network (compressibility). In this study we have experimentally examined how both these parameter change with resin volume fraction as pressure is applied and consolidation proceeds. For a unidirectional fiber bed, the Kozeny-Carman equation can be used to predict both the transverse (perpendicular to the laminate plies) permeability (Kozeny constant, K′z = 11) and the axial (parallel to the fibers) permeability (Kozeny constant, K′X = 0.57). The axial permeability was found to be dependent on the surface tension of the permeant. For a unidirectionally aligned fiber, the measured transverse permeabilities varied from 1.1 × 10-10 cm2 to 12. × 10-9 cm2 while the axial values varied from 2.1 × 10-9 to 4.4 × 10-8 cm2 for a liquid volume fraction range of 0.25 to 0.5. Axial permeability measurements indicate that the permeability decreases with increasing off-axis angle × (measured from the laminate axial direction). The off-axis permeability behavior can be described by a modified Kozeny-Carman equation. The fiber network compressibility can be described with a logarithmic relation which has been found valid for a large number of consolidated soils.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311411
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  • 7
    Electronic Resource
    Electronic Resource
    Pultruded fiber reinforced thermoplastic poly(methyl methacrylate) composites. Part I. Correlation of processing parameters for optimizing the process (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1086-1093 
    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 effect of processing parameters on the properties (tensile, flexural strength and modulus and impact strength, etc.) of pultruded fiber reinforced poly(methyl methacrylate) (PMMA) composites has been studied. The processing parameters investigated included pulling rate, die temperature, and postcure. Wetting of fibers by PMMA resin was complete, and the fiber bundles were evenly distributed in the PMMA matrix. The conversion, molecular weight and viscosity of MMA prepolymer were studied by 1H-NMR, GPC and Brookfield viscometer. The optimum die temperature was determined from DSC diagram, molecular weight measurement and from the polymerization rate. The mechanical properties increased with the increasing postcure temperature and decreasing pulling rate and die temperature.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311503
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  • 8
    Electronic Resource
    Electronic Resource
    Advanced process control for injection molding (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1081-1085 
    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 deals with the application of advanced control strategies to an injection molding process. Of particular interest is the control of one variable during the cooling phase of the molding process. Due to the cyclic dynamic nature of injection molding, the controlled variable must be regulated over a short cycle; the full process is completed within 10 seconds. Therefore, a key control objective is rapid setpoint regulation. A closed-loop strategy has been implemented for the regulation of pressure within the mold during the cooling cycle. First order plus dead time models of the process have been identified from plant step responses. The performance of several control algorithms for this process are compared in simulation studies. These algorithms have given comparable regulatory and servo responses. Finally, the effectiveness of the closed loop controi system has been demonstrated experimentally using the PI algorithm. Simulated and experimental results are in excellent agreement.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311502
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  • 9
    Electronic Resource
    Electronic Resource
    Pultruded fiber reinforced thermoplastic poly(methyl methacrylate) composites. Part II: Mechanical and thermal properties (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1094-1100 
    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 process has been developed to manufacture poly(methyl methacrylate) (PMMA) pultruded parts. The mechanical and dynamic mechanical properties, environmental effects, postformability of pultruded composites and properties of various fiber (glass, carbon and Kevlar 49 aramid fiber) reinforced PMMA composites have been studied. Results show that the mechanical and thermal properties (i.e. tensile strength, flexural strength and modulus, impact strength and HDT) increase with fiber content. Kevlar fiber/PMMA composites possess the highest impact strength and HDT, while carbon fiber/PMMA composites show the highest tensile strength, tensile and flexural modulus, and glass fiber/PMMA composites show the highest flexural strength. Experimental tensile strengths of all composites except carbon fiber/PMMA composites follow the rule of mixtures. The deviation of carbon fiber/PMMA composite is due to the fiber breakage during processing. Pultruded glass fiber reinforced PMMA composites exhibit good weather resistance. They can be postformed by thermoforming, and mechanical properties can be improved by postforming. The dynamic shear storage modulus (G′) of pultruded glass fiber reinforced PMMA composites increased with decreasing pulling rate, and G′ was higher than that of pultruded Nylon 6 and polyester composites.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311504
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal properties and morphology of hydrostatically extruded polypropylene (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1101-1107 
    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 melting point, specific heat, and morphology and hydrostatically extruded polypropylene (PP) were studied to clarify the plastic deformation of three different parts of the extrudates (periphery, intermediate, and core) parallel to the direction of hydrostatic extrusion. Differential scanning calorimeter (DSC) measurements showed that, for all the parts studied, the peak and the end-of-transition, temperatures had a minimum value at a percentage reduction in area, R, of 50% Similar behavior was observed for the specific heat evaluated at several temperatures below the melting point. The morphological structure observed by use of a polarizing microscope indicated that the shape- of spherulites above R = 50% changed from spherulitic to elliptic. It is suggested that the pronounced changes taking place around R = 50% are closely related to the marked bend in the extrusion pressure versus extrusion ratio curve which takes place at the same R value. The molecular chains in the coarse spherulites appear to be deformed below R = 50% in such a way that finer spherulites are formed; but at R values above 50% the presence of elliptic spherulites implies that non-uniform deformation is present under higher hydrostatic pressure of extrusion.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311505
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  • 11
    Electronic Resource
    Electronic Resource
    Adaptive pressure control for melt spinning processes (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1108-1112 
    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: Indirect adaptive control of the pressure of an extruder for melt spinning processes was investigated. The controller was a proportional-integral-derivative. (PID) one. An identified model for the pressure system was determined by using weighted least-squares estimation with an adjustable Identification interval. On-line tuning of the PID controller based on the identified model was then carried out. Difficulties in determining the proper model and controller tuning were avoided. The experiment, carried out with a pilot-type melt spinning machine, resulted in higher quality fiber production.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311506
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  • 12
    Electronic Resource
    Electronic Resource
    Studies on the theory of single screw plasticating extrusion. Part I: A new experimental method for extrusion (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1113-1116 
    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 extruder specially designed for the study of the single-screw plasticating extrusion process was constructed. Its barrel is equipped with glass windows which are located on both sides of it so that the full process of plasticating extrusion, solid conveying, melting, and melt conveying, can be clearly observed and recorded with photos and video recordings through the transparent windows. The solid profile X/W, the velocity of the solid bed Vsz, the forming positions of the upper melt film and the melt pool, and the position at which the break-up of solid bed occurs, was easily determined with good accuracy. Many dynamic characters of the plasticating extrusion, such as the non-plug solid conveying, the process of the break-up of the solid bed and the disappearance of the, broken pieces of solid, were also observed in the experiments.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311507
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  • 13
    Electronic Resource
    Electronic Resource
    The separate roles of phase structure and interfacial adhesion in toughening a brittle polymer (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1695-1702 
    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 effects of rubber particle size and rubber/matrix adhesion on the impact properties of a brittle polymer have been separated using polystyrene (PS)/acrylonitrile-butadiene rubber (NBR) as a model system in which interfacial chemical reaction could be controlled. It has been proven that the interfacial adhesion between the rubber phase and the PS matrix not only greatly aids in reducing the rubber particle size but also plays a further role in improving the impact properties of the matrix polymer. The impact energies of PS/NBR blends with interfacial chemical bonding are four to ten times as high as those without interfacial bonding for the same average rubber particle size. However, at temperatures below the glass transition temperature of the rubber, there is no difference in impact energies with or without interfacial chemical bonding. It has been found that the optimum rubber particle size for toughening PS is influenced by interfacial adhesion. Smaller optimum rubber particle size is observed for blends with greater amounts of interfacial chemical bonding.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322207
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  • 14
    Electronic Resource
    Electronic Resource
    Compatibilized blends of polyamide-6 and polyethylene (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1703-1710 
    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 increasing number of polymer alloys made by reactive processing of a compatibilizer precursor (CP) to form the compatibilizer in situ have appeared in recent years. Literature reports on compatibilization studies have focused on interactions of chemistry-morphology, processing-morphology, morphology-rheology, morphology-properties, etc. In commercial alloys, the interaction of chemistry and processing results in a material that has a balance of physical properties and rheological behavior. To maximize the contribution of each phase, it is of interest to be near the phase inversion region. In this work, maleic anhydride functionalized polyethylene is used as an effective CP for polyamide/polyethylene blends. In blends containing 50% nylon 6, the melt viscosity of the alloy increases exponentially as the ratio of CP to polyethylene increases though the morphology remains dispersed polyamide 6. High ratios of CP/PE are desired for toughness, alloys containing lesser amounts of CP exhibit better processability. The balance of toughness and processability is shown to be affected by the molecular weight of the CP.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322208
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  • 15
    Electronic Resource
    Electronic Resource
    Modeling of mold filling process for powder injection molding (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1137-1148 
    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 mold filling process has been modeled for the injection molding of different polymer-based binders and powder-polymer mixtures. It is essentially a two dimensional non-Newtonian fluid flow analysis in a non-isothermal environment. A complete analysis is accomplished by combining a finite element method and control volume technique to describe an increment of flow front movement, whereas a finite difference method is used to solve the energy equation to characterize the temperature distribution. Numerical results are compared to exact solutions for a circular ring cavity using a power law fluid model under an isothermal condition. Comparison of computed results against published data for a simple circular disk shows good agreement between the two analysis methods. After making selected comparison studies, it is demonstrated that the filling process in Powder Injection Modeling with different combination of powder-polymer mixtures is markedly dependent on specific combinations of powder; and polymer based binders. Computed flow front results for a rectangular cavity also compared favorably against the data for a power law fluid model under non-isothermal conditions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311511
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  • 16
    Electronic Resource
    Electronic Resource
    Injection mold flashing of liquid crystalline polymersPaper presented as poster at 6th Annual Meeting of The Polymer Processing Society, Nice, Apr. 17-20, 1990. (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1130-1136 
    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: Thermotropic polyesters, such as Vectra (Hoechst Celanese), have excellent moldability for intricate parts that require high precision of form, such as electronic connectors. Two apparently contradictory aspects of molding behavior contribute to the moldability. On the one hand, the low viscosity of the liquid crystalline polymer (LCP) at high shear rates favors ease of filling molds that contain long, thin paths. On the other, parts molded from LCP have little or no flash to interfere with the functioning of the parts.There has apparently been little work on the rheological aspects of flash formation. An approximate analysis is made by considering that the flash is the result of melt being extruded from the mold cavity into a slit at the mold parting line. The driving force for the extrusion is the injection pressure. The flow is assumed to be isothermal until solidification occurs, at a time that depends on the thickness of the slit, on the thermal diffusivity of the melt, the melt and mold temperatures, and on the solidification temperature of the material. The viscosity is assumed to have power-law dependence on shear rate. It is found that when the aspect ratio (length to thickness) of the flash is small, its length is strongly dependent on the magnitude of the pressure drop at the contraction from the cavity to the slit.At the minimum pressure required to fill a mold, the flash length is predicted to be independent of the rheological and thermal properties of the melt, except for the power-law exponent. Differences in end correction can, however, account for different tendencies to flash at equal moldability.Comparison of the model with Richardson's analysis of freezing in a cavity suggests a correlation of the thermal properties of the melt with his parameter c, which is related to mold filling ability. Tests of the model and possible refinements are suggested.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311510
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  • 17
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    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.760311601
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  • 18
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    Modeling of the impregnation process during resin transfer molding (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1149-1156 
    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 has developed for simulating isothermal mold filling during resin transfer molding (RTM) of polymeric composites. The model takes into account the anisotropic nature of the fibrous reinforcement and change in viscosity of the polymer resin as a result of chemical reaction. The flow of impregnating resin through the fibrous network is described in terms of Darcy's law. The differential equations in the model are solved numerically using the finite element technique. The Galerkin finite element method is used for obtaining the pressure distribution. A characteristics based method is used to solve the non-linear hyperbolic mass balance equation. The finite element formulation facilitates computations involving the motion of the polymer resin front characterized by a free surface flow phenomenon.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311512
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  • 19
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    A 2-d numerical study of intermeshing self-wiping screws in biopolymer extrusion (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1157-1163 
    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 knowledge of flow behavior is important in the study of laminar flow in twin-screw extrusion processes to predict the velocity distribution and to understand the mixing process. The flow of a power law fluid in self-wiping twin-screw extruders is examined using a two-dimensional finite element analysis of a mid-channel section of intermeshing screws. Theory is compared with experiment using food biopolymer and plastic materials. Comparisons showing overprediction of throughputs, but similarities in behavior, suggest that this model could provide an upper limit for melt conveying. For most of the throughput range examined, pumping of intermeshing self-wiping screws appears to be almost independent of the power law flow index of the melt extruded, but the value of the flow index determines the degree of influence intermeshing has on the overall pressure gradient generated in the extruder.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311513
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  • 20
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    Optimization of the polymer melt thickness distribution on a cable of large diameter (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1165-1171 
    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 numerical method for analysis of isothermal non-Newtonian polymer melt flow in narrow channels of complex shape is described. This method is applied to the flow in a cable-covering crosshead. The volumetric flow field is calculated and the melt thickness distribution proves to be strongly nonuniform. A series of modified cannel geometries are suggested and the volumetric flow rates in these channels are calculated. One of these channels, which gives a substantially more uniform unsulation thickness, is shown as an improved channel design.
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    URL: http://dx.doi.org/10.1002/pen.760311602
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    Effect of filler content and additives on the extrudate swell of polyethylene pipe resin (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1176-1181 
    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 certain extrusion operations, particularly the production of plastic pressure pipe, it would be desirable to be able to control the degree and direction of molecular orientation. While dies can be designed to generate various types of orientation, most of this is lost at the die exit due to extrudate swell. It is known that substantial loadings of nonreinforcing filler can inhibit swell, and the objective of this study was to examine the effects of particle size and loading and of the use of coupling agents on extrudatee swell of CaCO3-filled medium-density polyethylene pipe resin. Swell was measured as a function of time by extruding into oil having the same density and temperature as the extrudate. In addition, the storage and loss moduli of all samples were measured, and, the relaxation spectra were calculated. The maximum degree of swell suppression was observed for a compound containing 30 wt. percent of 0.4 micron particles treated with stearic acid. Surprisingly, the use of coupling agent increased the degree of swell.
    Additional Material: 18 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760311604
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    Extrudate swell of high density polyethylene. Part II: Time dependency and effects of cooling and sagging (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1750-1754 
    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: For two high density polyethylene resins, the isothermal time dependency of extrudate swell has been measured. Very minor differences in the large molecular weight part of the molecular weight distribution, hardly detectable with gel permeation chromatography and low angle laser light scattering techniques, dramatically influence the time dependency of extrudate swell as well as the maximum swell attainable. The presence of larger molecules in sample 802 than in 801 is reflected in a lower short time (after seconds) and a larger long time (after minutes) or maximum extrudate swell value. Extruding the polymers through a capillary die L:D = 30:2 mm into air at ambient temperature allows only the short time swelling behavior to be observed, because cooling and sagging of the strand.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760322303
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    Analysis of unsaturated polyester-polyurethane interpenetrating polymer networks. I: Reaction kinetics and viscosity model (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1182-1188 
    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 reaction kinetics and viscosity behavior during the reaction injection molding (RIM) process of unsaturated polyester (UPE)-Polyurethane (PU) interpenetrating polymer networks (IPNs) were studied. The interaction between the reactants of the component polymers was reflected in the reaction kinetic model. The intermediate reaction products having a certain conversion level were prepared in order to obtain the conversion dependence of viscosity. The composition dependence of blend viscosity was also evaluated for, the oligomeric mixture.
    Additional Material: 14 Ill.
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    Effect of crystallization conditions on the morphological structure of ethylene-1-butene copolymers obtained by different ziegler-natta catalyst systems (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1189-1193 
    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: Four ethylene- 1 -butene copolymers of about the same comonomer content but obtained with different supported Ziegler-Natta catalyst systems have been studied. The effects of the catalyst and the crystallization conditions on the morphological structure have been analyzed. These two factors'clearly affect the melting endotherms and the most probable crystallite thickness of the copolymers, although no important differences were found in the crystalline contents. The catalyst system influences the melting pattern due to changes in the chemical composition distribution, i.e., variations in the comonomer content between chains of different molecular weight.
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    The effects of varied reactant ratios on the polymeric structures of stannous dicarboxylates (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1194-1199 
    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: Some polymeric Sn(II) dicarboxylates have been produced with good yields from aqueous solution via a double decomposition reaction using varied nonstoichiometric molar proportions of the reactants. They were obtained as highly viscous pale yellow liquids formed into separate denser phases in the precipitation bath. The highly viscous precipitates were drawn directly into fibers. Meltspun polymeric stannous dicarboxylates produced fibers which were only flexible above the glass transition temperature, Tg.When the aliphatic dicarboxylic acids were replaced with their aromatic counterparts similar highly viscous liquids were obtained, but they solidified almost at the instant of formation.
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    Electrical conductivity in heterogeneous polymer systems. V (1): Further experimental evidence for a phase transition at the critical volume concentration (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1200-1206 
    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 dispersion/flocculation phase transition model for the conductivity jump at the critical volume concentration of a conductive phase in an insulating matrix polymer is discussed. New experimental-data including: SEM evaluations of the “seam” structure, excess pyrolytic residue analysis, BET measurements of dependence on conductive phase content, and temperature dependence of conductivity are presented for supporting the new model. Finally a first qualitative step towards a new non-equilibrium thermodynamical description of these dissipative structures will be described.
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    Phase morphology characterization and ultimate mechanical properties of 60/40 PC/SAN blend: Influence of the acrylonitrile content of SAN (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1215-1221 
    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 tensile stress-strain properties of blends having a 60/40 weight ratio of polycarbonate of bisphenol-A (PC) and styrene-acrylonitrile copolymers (SAN) have been investigated for a range of SAN copolymers with different AN levels. It is clearly demonstrated that the phase morphology of these, blends and the acrylonitrile (AN) content of the SAN component are important factors with respect to the ultimate mechanical properties (tensile strength and elongation at fracture). Following injection molding, a very fine phase distribution is observed for blends with SAN components containing 15 to 29% AN. By annealing of the blends at 200°C, i.e. above Tg(PC), it has been possible to obtain different degrees of domain sizes. From this range of morphologies, quite similar phase structures can selected differing only in AN-content of the SAN blend components. This allows a systematic investigation of the effect of the AN-content on the tensile stress-strain. Properties of PC/SAN blends. The elongation at fracture exhibits an optimum for blends with SAN containing 24% AN. A coarsening of the phase morphology only results in a decrease of the ductility and not in a shift of the optimum. The maximum tensile stress exhibits a sigmoidal trend as a function of the AN-content. This parameter remains constant for a typical -PC/SAN blend with different morphologies.
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    URL: http://dx.doi.org/10.1002/pen.760311610
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    Anisotropic in-plane permeability of fabric media (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1233-1239 
    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 elegant procedure is proposed for obtaining components of the orthotropic or anisotropic in-plane permeability tensor from experimental data on flow front position and time. A radial flow geometry allows the shape of the advancing flow front to be dictated by the in-plane permeability of the fabric media. The directional permeabilities in the fabric plane are directly calculated from fluid and fabric properties together with data from the mold filling experiment (resin injection pressure and flow front position with time). The simplicity of the apparatus and proposed analytical procedure permit easy testing and comparison of different types of fibrous media.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760311613
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    Development of polymer blend morphology during compounding in a twin-screw extruder. Part I: Droplet dispersion and coalescence - a review (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1824-1833 
    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: The theoretical and experimental data on the breakup of droplets are reviewed. Several factors influence development of droplets: flow type and its intensity, viscosity ratio, elasticity of polymers, composition, thermodynamic interactions, time, etc. For Newtonian systems undergoing small, linear deformation, both the viscosity ratio and the capillary number control deformability of drops. On the other hand, the breakup process can be described by the dimensionless breakup time and the critical capillary number. Drops are more efficiently broken in elongational flow than in shear, especially when the viscosity ratio λ ≥ 3. The drop deformation and breakup seems to be more difficult in viscoelastic systems than in Newtonian ones. There is no theory able to describe the deformability of viscoelastic droplet suspended in a viscoelastic or even Newtonian medium. The effect of droplets coalescence on the final morphology ought to be considered, even at low concentration of the dispersed phase, φd ≥ 0.005. Several drop breakup and coalescence theories were briefly reviewed. However, they are of little direct use for quantitative prediction of the polymer blend morphology during compounding in a twin-screw extruder. Their value is limited to serving as general guides to the process modeling.
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    Development of polymer blend morphology during compounding in a twin-screw extruder. Part II: Theoretical derivations (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1834-1845 
    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 Part II of the work, the intermeshing twin-screw extruder is briefly described and the theoretical procedures used to model its operation are summarized. Based on the microrheological considerations discussed in Part I, a predictive procedure of the morphology evolution during compounding of two immiscible polymers is proposed. In this first generation model, only the shear flow effects are considered. Furthermore, to avoid complications due to coalescence a low concentration of the dispersed phase was assumed. In the procedure, two drop breakup mechanisms are discussed. The first assumes that the drops do not break under flow while the second postulates that breakup occurs under flow. Two dispersion mechanisms are considered, the first postulating continuously increasing polydispersity of drop size and the second postulating that drop polydispersity is inversely proportional to deformation strain. The influence of the screw configuration and operating conditions on blend morphology evolution is studied. It is expected that the computed drop size distribution provides limiting values for the experimental data. Dependency of predicted morphology on operating conditions is also investigated. Increasing screw rotating speed (resulting in increasing energy consumption) and decreasing throughput (resulting in decreasing productivity) lead to prediction of finer drop size. In practice, therefore, a compromise would be required. The proposed procedure is limited to melt flow (excluding the die region) within the region of large capillary parameter values, k 〉 4kcrit.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760322406
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    Orientation of miscible and immiscible polymer blends (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1857-1862 
    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: Polystyrene (PS) and poly(vinylmethylether) (PVME) were used to study the orientation of miscible and immiscible polymer blends. A miscible blend containing 60 wt% PS was prepared by casting the sample from a benzene solution. The immiscible blend was made by annealing the initially miscible mixture above its lower critical solution temperature for different times and temperatures. Fourier transform infrared spectroscopy and birefringence were used to measure the orientation of PS and PVME, before and after phase separation. Stress-strain curves were also measured for the two types of systems. It was found that the two polymers orient differently and that phase separation induces an increase in the overall orientation of the mixture, in the modulus and in PS orientation. The differences observed between pure PS and PS in the blend were attributed to changes in specific interactions and density of entanglements. The variations with phase separation were attributed to a change in the morphology of the system.
    Additional Material: 6 Ill.
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    Impact and compression response of composite materials containing fortifiers (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1310-1315 
    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 effect of adding fortifiers to an epoxy matrix on the response to impact and compression-after-impact properties of carbon fabric/epoxy laminates was investigated. The experimental work included determining laminate compression strength, absorbed energy from impact, damage area and compression-after-impact strength for an impact energy level of 21 joules per centimeter of thickness. This paper presents the results from this investigation and discusses the relationship between neat resin properties (with and without fortifiers) and the laminate properties.
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    Injection molding of long fiber-reinforced thermoplastics: A comparison of extruded and pultruded materials with direct addition of roving strands (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1316-1329 
    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 injection molding process is proposed whereby roving strands are directly incorporated into the polymer melt by using a reciprocating-screw-plasticating unit. The direct incorporation of continuous fibers (DIF) offers the possibility to substitute the relatively expensive and limited pultrusion process currently used to produce long fiber pellets. In this preliminary study experimental investigations on glass fiber-reinforced polyamide-6,6 are carried out, starting with short and long fiber pellets in comparison to the direct incorporation of roving strands into the polymer melt. Some special aspects of the processing of long fiber-reinforced thermoplastics are discussed. The results of fundamental mechanical and physical property investigations are presented, including fiber length distribution, fiber concentration, fiber bundling/clustering and fiber orientation. The influence of fiber diameter and fineness of strands (tex) on the feed-in behavior and the resulting property profile is also discussed.
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    Influence of maleic anhydride as a coupling agent on the performance of wood fiber-polystyrene composites (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1351-1357 
    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 lack of polar groups in thermoplastics (e.g., in polystyrene) provides low adhesion with cellulosic fibers. To improve compatibility between reinforcement and matrix, maleic anhydride (MA) was selected as a coupling agent for wood fiber-filled polystyrene composites. In general, the mechanical properties improved along with increased concentrations of MA, initiator (e.g., benzoyl peroxide) and wood fiber up to a certain limit and then decreased. The concentrations of MA and fiber which produced maximum improvements in the mechanical properties varied according to wood species, pulping techniques and type of polystyrene. Moreover, properties were further enhanced when another coupling agent (e.g., isocyanate) was used in addition to the MA.
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    URL: http://dx.doi.org/10.1002/pen.760311810
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    Computer simulations of crystallinity gradients developed in injection molding of slowly crystallizing polymers (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1372-1385 
    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 is developed to simulate the crystallinity gradients developed in injection molding of slowly crystallizing polymers. In this model, effects of nonisothermal and stress-induced crystallization kinetics are taken into account through phenomenological relationships. Computer simulations included calculations of the temperature, velocity, and pressure distributions as well as two dimensional crystallinity distributions in the final products. In addition, effects of various processing conditions: mold temperature, injection flow rate, and holding time are also included in the calculations. The crystallinity gradients obtained through computer simulations agree with the experimental results obtained with poly (p-phenylene sulfide) under a variety of processing conditions.
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    Effects of air entrainment on the rheology of concentrated suspensions during continuous processing (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1386-1392 
    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: Samples of a concentrated suspension were systematically collected from the mixing volume of a continuous processor. The large amplitude oscillatory shear behavior of the samples was found to be significantly affected by the screw configuration employed and the location. Microstructural analyses employing nuclear magnetic resonance imaging, wide-angle X-ray diffraction and X-ray radioscopy revealed substantial entrainment of air into the suspension during continuous processing. The volume fraction of the entrained air increased with geometries and operating conditions leading to partially full channels. Overall, air entrainment is identified as a dominant factor in the development of the microstructure and the rheology of concentrated suspensions and should be considered in their optimum processing.
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    Development of cracks in injection moldings of poly (2,6-dimethyl-1, 4 phenylene ether) (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1393-1399 
    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: Cracks in injection molded articles adversely affect their appearance as well as their ultimate properties. In this study, we have investigated the spontaneous development of cracks in samples molded from an engineering plastic in the absence of external loading. The specimens of a well characterized poly(2,6-dimethyl-1,4 phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The initiation and development of cracks in the molded articles were monitored for a period of eighty weeks. The presence and the frequency of the cracks were found to depend on the operating conditions employed during the molding, the shape of the cavity, the presence of Irregularities at the mold surface, and the particular location observed. The results were elucidated under the light of the results of microstructural analyses including residual stress and birefringence distributions on both compression and injection molded specimens of the engineering plastic.
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    Dynamic modeling of the mold filling process in an injection molding machine (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1417-1425 
    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 for the study of the mold filling process in an injection molding machine. The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics. The mold filling process can be approximated by the transient phenomenon of the non-Newtonian fluids flowing through a closed conduit. The comparison between the experimental results and the theoretical simulation indicate that the nonlinear model is a reasonable representation of the mold filling dynamics when the acrylonitrile-butadiene-styrene (ABS) is injected into a disk shape mold. The actuation system dynamics of an injection molding machine are also investigated. The results indicate that the nonlinear model can also adequately predict the transient behavior of the actuation system.
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    Isothermal and dynamic reaction kinetics of high performance epoxy matrices (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1426-1433 
    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 reaction kinetics of the epoxy matrix of a commercial prepreg for high performance composites, based on tetraglycidyl diamino diphenyl methanediamino diphenyl sulfone (TGDDM-DDS) formulation, has been characterized by differential scanning calorimetry (DSC). A phenomenological kinetic model, able to describe the behavior of the system during normal processing operations has been formulated. The diffusion control phenomena, related to the evolution of the glass transition temperature as a function of the degree of polymerization, has been considered in the formulation of the kinetic model. Isothermal and dynamic tests have been used to calculate the model parameters and to verify the proposed model. The model is able to describe incomplete reactions in isothermal tests and heating rate dependence of dynamic test thermograms, and it has been also successfully applied to DSC experiments performed with complex thermal conditions commonly used in the processing of high performance composites.
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    Effects of thermoplastic additives on the cure of unsaturated polyester resins (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1450-1460 
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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: Thermoplastic additives tend to promote the phase separation during the reaction of unsaturated polyester resins. Consequently, they reduce the amount of shrinkage during curing. Several thermoplastic additives which resulted in significant different microstructure of cured resins were investigated. The effects of microstr acture formation on the sol-gel transition, reaction kinetics, and gelation time were studied. The mechanism of microstructure formation and causes of macro-gelation were explained by the influence of thermoplastic additives on the particle formation rate and inter-particle reaction rate during curing.
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    URL: http://dx.doi.org/10.1002/pen.760312003
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    Property modifications in poly(p-phenylene benzobisthiazole) fibers with high-tension and high-temperature drying versus postprocessing heat treatment (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1441-1449 
    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: Modifications in the structure and mechanics of poly(p-phenylene benzobisthiazole) (PBT) fibers have been attempted through high-tension and hightemperature drying and subsequent postprocessing heat treatment experiments. High-tension drying results in an enhancement in tensile properties by offsetting compressive shrinkage stresses during the drying process and improving the molecular alignment within the fiber. Elevated temperature drying under tension further improves the extent and perfection of the lateral molecular order. The increased molecular ordering and improved tensile properties are believed to result from the removal of water and residual acid at elevated temperatures. The final fiber properties after subsequent postprocessing heat treatment are independent of the drying conditions. These results suggest that the ultimate fiber properties are a function of the total strain imposed in all the processing operations (dry jet stretch region, coagulation and drying process, postprocessing heat treatment). The attainment of the fiber's theoretical highmodulus/high-strength properties appears limited by defects such as voids and internal stresses which, in turn, restrict the amount of strain imposed during the fiber process.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760312002
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    Dynamic mechanical response of model epoxy networks in the glassy state (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1476-1482 
    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 dynamic mechanical properties of model epoxy-amine networks are investigated in the glassy state over a wide range of frequencies, at temperatures between 123 K and 350 K. The effects of crosslink density and network chain flexibility on the β relaxation are examined. Motions responsible for the β process begin to develop at the same temperature, whatever the crosslink density. However, an increase in crosslink density is accompanied by an increase in amplitude and a broadening towards high temperatures of both damping tan δ and loss modulus E″. This effect is responsible for the decrease of elastic modulus E′ at room temperature with increasing crosslink density.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760312006
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    Examination of dimethacrylate inhomogeneity by solvent swelling techniques (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1483-1492 
    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: Dimethacrylate monomers polymerize to form highly crosslinked networks with an inhomogeneous distribution of regions of low and high crosslink density. The systems are probed in this work by observing the effects of solvents (nitrobenzene and water) on dynamic mechanical measurements, diffusion kinetics and fracture toughness experiments. Dynamic mechanical analysis showed that the addition of nitrobenzene is found to have little effect on the position of the glass transition or secondary relaxations for solvent levels of under 3.5 mass %. It is proposed that solvents initially diffuse into low crosslink density regions, impinging little on the methacrylate mainchains which reside largely in regions of high crosslink density. Only at higher solvent concentrations do these chains become plasticized. Confirmation of heterogeneity is provided by diffusion analysis of isothermal solvent uptake. This is also interpreted interpreted in terms of a two-stage diffusion process due to differential rates of sorption which occur in different microregions. Weighing of the water uptake of samples suspended in water indicated that some 30% of water absorbed at equilibrium exists within void regions. Addition of water causes the fracture mechanism to change from a ‘stick-slip’ mechanism characteristic of brittle polymers to stable crack growth with a lower fracture toughness. This is also attributed to differential swelling of the material causing internal stresses which aid material failure.
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    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    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.760312101
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    Styrene maleic anhydride and styrene glycidyl methacrylate copolymers as in situ reactive compatibilizers of polystyrene/nylon 6,6 blends (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1509-1519 
    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 reactive type copolymers styrene maleic, anhydride (SMA) and styrene glycidyl methacrylate (SG) are used as in situ compatibilizers in polyblends of polystyrene (PS) and nylon 6, 6 (N66). Both copolymers can react with N66 to form copolymers as effective compatibilizers to reduce interfacial tension and increase phase adhesion. However, the toughness of the compatibilized blends is significantly lower than of the corresponding noncompatibilized blends. Only a small fraction of SMA is actually reacted in a typical melt blending, and SG copolymer seems to be more reactive than SMA. The unreacted copolymers are expected to be distributed mostly in the PS phase because of their structural similarity. The reacted copolymers are not exclusively distributed along the interface; some may distribute in both matrices. SMA is known as a very brittle polymer, and the way it is distributed can greatly influence the toughness of the resulting blends. PS is also very brittle relative to N66, and moreover a high amount of SMA in the N66 phase is detrimental since N66 is responsible for the toughness of PS/N66 blends. The better compatibilized blends have the tendency to bring more SMA and reacted SMA into the N66 phase. The relative detrimental effect on the inherent toughness of N66 is much more severe than in case of PS, if they contain the same amount of SMA. This study demonstrates that polyblends with good compatibilizers do not guarantee toughness improvement. The way the compatibilizers affect the inherent properties of the matrix needs also to be taken into consideration.
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    The running-in and steady-state coefficient of friction of some engineering thermoplastics (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 70-74 
    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 dry friction properties of three engineering thermoplastics, ultra high-molecular-weight polyethylene (UHMWPE), polyoxymethylene (POW) and polyamide 66 (PA 66), have been investigated using a plane on plane contact. During running-in, the steady-state of the friction coincides with stable values for the surface temperature of the slider. The proper trend as well as the correct order of magnitude are observed between the measured surface temperatures and those calculated using the equation of Lancaster. The increase of the run-in friction as function of the Pv factor could be well correlated by μ(t) = μss - Pv-nexp(- 2 104 t), where μss is the steady-state value of the coefficient of friction, n is a constant depending on the material tested. A decrease of μss with increasing load for UHMWPE and POM indicates that friction is primarily the result of adhesion. However, for the PA 66, the opposite is valid, assuming that in this case the high Tg of this material may play an important role. Friction increases as the rugosity of specimen diminishes and as speed increases. Finally, the coefficient of friction could be well correlated by μ = kPmexp(βv) where k, m, and β are constants depending on roughness and type of material.
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    Crystallization kinetics of poly(ethylene terephthalate): Cmemory effect of shear history (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 83-91 
    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 memory effect of shear history was studied with poly(ethylene terephthalate) (PET) prepared under different shear conditions of 11.7 to 1168 s-1 in a capillary rheometer. The shear history of PET resin led to a memory effect, which in turn affected the crystallization kinetics. The crystallization rate increased with increasing shear rate. Double peaks of heating crystallization exotherms and a low value of Avrami exponent appeared at low shear rates, which was attributed to the existence of crystallization processes with different rates; one was the fast process involving the disentangled molecules that persisted during melting, and the other was the slow process involving the highly entangled molecules. The change of instantanenous Avrami exponent and overall crystallization rate constant was in good agreement with the expected trends assuming coexistence of the two crystallization processes. The crystallization kinetics of PET with shear history could be regarded as a growth rate decrease problem to be interpreted by the modified Avrami equation, 1 - Vc = exp[- K·f(t)n], when the fast process dominated the overall crystallization. The effect of shear history was reduced because of the relaxation process as the holding time in melt state before crystallization was increased.
    Additional Material: 15 Ill.
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    Dielectric characterization of water sorption in epoxy resin matrices (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 75-82 
    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: Water sorption in epoxy based materials was analyzed by dielectric spectroscopy using remote sensors. A method to determine diffusion coefficients from the changes in permittivity during water absorption is proposed and was verified experimentally by comparison with standard water gain measurements. Although the technique is limited by electrode polarization phenomena, it is sensitive to the presence of water molecules and is capable of detecting different levels of water concentration as a function of frequency. The utilization of remote sensors demonstrated the capability of dielectric analysis to be applied both in the laboratory environment, and on a larger scale, as a nondestructive technique for monitoring environmental changes in actual polymer matrix composite parts.
    Additional Material: 11 Ill.
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    Kinetic modeling of the epoxidation of natural rubber with in-situ-formed peracid (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 92-96 
    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 the presence of excess hydrogen peroxide and formic acid the latex stage epoxidation of natural rubber is pseudo-first order in nature. A kinetic model is developed to predict the maximum extent of epoxidation for the reaction system and its variation with increasing acid concentration. Th dependence of the overall rate constant on acid concentration is also studied.
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    Predicting the behavior of nonlinear viscoelastic materials under spring loading (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 97-99 
    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: Structural parts made of plastics are usually tested under creep loading conditions, i.e., the stress is applied almost suddenly and then kept constant, while defomation is measured. In practice, however it happens that such a structural part is loaded by an elastic member (for example, by a spring). In this case, the acting force is no longer constant; it decreases in the course of time, while the deformation of the specimen increases (and, obviously, that of the spring decreases). The present paper describes a numerical approach for the solution of this problem, based on the assumption that the creep behavior of the material is known. An example is presented.
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    Deformation and fracture of glass bead/ CTBN-rubber/epoxy composites (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 100-107 
    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: Carboxyl-terminated butadiene-acrylonitrile-rubber decreases modulus and yield stress of the studied epoxy but increases fracture toughness. The addition of glass bead compensates for the loss in modulus but has little effect on yield stress. However, it significantly contributes to the fracture toughness by providing additional mechanisms for toughening of both the unmodified and rubber-modified epoxy. For the toughened epoxies studied, fracture surfaces gave only limited information on fracture mechanisms since significant energy absorption also occurs in the material below the fracture surface. Suggestions for suitable material compositions for fiber composite matrices are given.
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    The effect of reactive monomers and functional polymers on the mechanical properties of an unsaturated polyester resin (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 115-121 
    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-purpose unsaturated polyester resin with 2:1 mol ratio of styrene to polyester unsaturation was modified with three vinyl monomers and two hydroxyl terminated polybutadienes. Tensile, flexural, and puncture impact properties were examined. The three acrylate monomers were tetraethylene glycol dimethylacrylate, 1,3 butylene glycol dimethacrylate, and trimethylpropane trimethylacrylate with weight percents of 2.5, 5, 15, and 30. Two hydroxyl terminated polybutadienes with slightly different contents of hydroxyl functionality were also employed in the weight percents of 2.5, 5.0, and 10.0. Results showed that an increase in the number of crosslinks and crosslink density resulted in a deterioration in the mechanical properties. The addition of an immiscible polybutadiene polymer to the polyester resin also showed a decrease in the mechanical performance of the resulting thermoset materials.
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    Masthead (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993) 
    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.760330301
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    Dynamic melt rheology. II: Re-examining the relationship of g′ in oscillatory rheometry to the melt elasticity (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 122-124 
    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 oscillatory rheometry, since the dynamic storage modulus (G′) represents the elastic component of the viscoelastic melt, it has been a rather common practice to associate it with the melt elasticity. Although this assumption might be valid in many instances, there can be exceptions as well. In the present study, we have chosen polypropylene/talc system to demonstrate an exception. For example, the melt elasticity decreases with increasing talc content as revealed by extrudate die swell, entrance pressure drop, and elastic compliance measurements; the opposite trend being reflected by G′. We can envision similar exceptions when stiffening agents are added to a polymer melt, e.g., rigid rod molecules. We are suggesting that G′ represents the elastic modulus or stiffness of the melt, which in certain situations might not reflect elasticity, i.e., the ability of a melt to recover from a deformation. The implication of the present manuscript is that caution be exercised when relating G′ to the melt elasticity of a polymer.
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    Viscoelastic properties of a 60 mol% para-hydroxybenzoic acid/40 mol% poly(ethylene terephthalate) liquid crystalline copolyester. I: Effect of temperature historyPart of this work was originally presented at the 39th Annual Meeting of the Society of Polymer Science, Japan, in Kyoto, May 29-31, 1990. (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 108-114 
    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 paper, the rheology of a 60 mol% para-hydroxybenzoic acid (PHB)/40 mol% poly(ethylene terephthalate) (PET) copolyester (herein referred to as PHB60/PET40) produced by Unitika Co., Japan, was investigated using viscoelastic property temperature sweeps. In addition to the large-scale hysteresis (super-cooling) of viscoelastic properties that has also been seen with other PHB-based materials, in which it is possible for several PHB linkages to occur side by side along the polymer backbone (most notably the PHB60/PET40 polymer produced by Tennessee Eastman), smaller-scale viscoelastic transitions, one present in heating, and believed to be associated with the partial isotropization of liquid crystalline material, and the other apparent on cooling, occurring at a lower temperature than the first and thought to be associated with the opposite process, were observed. When overall mol% PHB composition along individual chains is considered, the well-defined appearance of the additional smaller-scale rheological transitions seen here is believed to be due to a unimodal composition distribution, rather than a bimodal distribution of which there is increasing evidence in the Tennessee Eastman materials. This difference is believed to be caused by differences in the preparation technique used for the Unitika version of the polymer.
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    Dielectric monitoring of the curing process in cyanoacrylate resin (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 125-131 
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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 cure monitoring of cyanoacrylate resin using a dielectric technique shows that in addition to the usual fast anionic polymerization step, there may be a secondary process involved over longer time scales. Two peaks are distinctly observed in the isothermal curing curves, and from the position of these at various temperatures, the activation energies of 0.4 eV and 0.17 eV could be derived. In cured cyanoacrylate resin, three relaxations were observed, viz., α, β, and γ, occurring at 152°c, 87°c, and 47°c, respectively (for 1 KHz measuring frequency), with activation energies of 1.3 eV, 0.56 eV, and 0.4 eV, respectively. The various results have been explained on the basis of secondary bond formation through the nitrile group, for which some evidence could be obtained from the infrared absorption spectra.
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    Analysis of the effects of internal heating and cooling during the rotational molding of plastics (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 132-139 
    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 rotational molding, shortening the cycle time is one of the most important requirements for increasing production rates and reducing product cost. A characteristic feature of the process is that the mold and plastic powder are heated from room temperature to the melting temperature of the plastic and then back to room temperature. In addition, in the vast majority of cases the heat input and subsequent heat extraction occur at the outside surface. In order to improve the heat transfer, this paper considers the effects of internal heating and cooling. A mathematical model has been developed in which an internal heating term can be incorporated. The experiments with rotomolding powders show that the predictions made by the model are accurate. In particular, it is found that the introduction of internal heating is very effective in shortening the cycle time and that the introduction of internal cooling in rotational molding provides a more uniform structure and less likelihood of warpage.
    Additional Material: 11 Ill.
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    Masthead (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    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.760312301
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    Migration and blooming of stabilizing antioxidants in polypropylene (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1610-1617 
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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: We have studied the migration of the hindered phenol, octadecyl-3,5-bis (1,1-dimethylethyl)-4-hydroxybenzenepropanoate, and the phosphite co-stabilizer tris 2,4-bis(1,1-dimethylethyl)phenylphosphite, out of films of polypropylene (nominal melt flow 3.5 g/10 min). Loss of additive from an initial 10% weight-% level in the polymer was followed by FTIR bands in the appropriate regions. Temperatures of 298 K, 313 K and 333 K were used. An attempt was made to analyze migration data using Fick's law for diffusion by means of a least squares fit. Octadecyl-3,5-bis (1.1-dim ethylethyl)-4-hydroxybenzenepropanoate diffused according to Fick's law with a temperature independent diffusion constant (D = 1.27 × 10-15 m2 S-1) to a steady state concentration of 7.2 % + -0.56 weight-%. The phosphite did not diffuse at all at 298 K and 313 K, but diffused with D = 8.1 × 10-16 m2 S-1 to a steady level at 333 K. Our interpretation of the phosphite migration data assumes that most of the phosphite in the sample is immobilized. A subset of the total phosphite level is free to diffuse to the surface of the polymer.
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    The influence of continuous stabilization on the properties of stabilized fibers and the final activated carbon fibers. Part I (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1618-1626 
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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: This study found that, during continuous stabilization and carbonization, the shrinkage behavior of polyacrylonitrile (PAN) fibers affects the morphology and properties of the stabilized fibers, the carbon fibers, and the final activated carbon fibers. In the stabilized fibers, a higher shrinkage of the PAN fibers during the stabilization process increased the oxygen content and the core proportion and decreased the formation of ladder polymers. The effect of the shrinkage behavior of the PAN fibers on the fracture surfaces of the stabilized fibers is discussed. A microstructure model of stabilized fibers is presented, depicting fine radial structure at the fiber center. When stabilized fibers were carbonized during a continuous carbonization process, a hole structure was found in the fiber center at the temperature of 800°C, and a hollow core was found at the temperature of 1300°C. The shrinkage behaviors during the stabilization stage and the formation of the hole and the hollow core in the fiber's center during the carbonization stage are discussed. The carbon fibers developed from shrunk stabilized fibers have a lower density and lower preferred orientation than fibers developed from unshrunk stabilized fibers. But the fibers developed in this new process have greater nitrogen and oxygen content, and have a greater porosity than the traditionally-produced fibers. The mechanical properties df the new and the traditional fibers are comparable. These characteristics are very valuable in the production of activated carbon fibers, which will be described in our next paper.
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    Processing of thermotropic liquid crystalline polymers and their blends - analysis of melt-spinning TLCP fibers (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 156-165 
    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: Isothermal melt-spinning of two thermotropic liquid crystalline polymers (TLCPs), a wholly aromatic copolyester KU-9211 (also named K161 from Bayer AG) and an aliphatic containing TLCP, PET/PHB60 (Tennessee Eastman), was studied to analyze the effect of processing conditions on fiber properties. Fibers were melt-spun from a capillary rheometer equipped with an isothermal chamber in which cross-flowed air was used as the cooling medium. The processing variables studied included the extrusion temperature, the extrusion rate, the cooling conditions, and the draw ratio. As-spun fibers were characterized by measuring storage moduli and molecular orientation parameters as a function of draw ratio under various processing conditions. Among the processing variables studied, the draw ratio was the primary factor in determining both the fiber modulus and the molecular orientation. The extrusion rate did not appear to affect the fiber properties within the range studied. The properties of K161 fibers were also dependent on the extrusion and cooling temperatures, while PET/PHB60 fibers were rather insensitive to the processing temperatures within data scatter and temperatures studied. A composite model based on a rigid-rod rotation mechanism and the deformation of nematic domains in an elongational flow field was used to model the experimental results and was compared with other theories available. Conformance of data to the composite model was obtained by use of a single temperature dependent parameter n, suggesting that the rigid-rod rotation mechanism could be used to predict the orientation development of TLCPs. The Halpin-Tsai equations and the orthotropic equation for angular dependence were used to describe the elastic properties of the TLCP fibers.
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    Reactive processing of polymer blends: Analysis of the change in morphological and interfacial parameters with processing (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 175-182 
    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 change in morphology and interface quantities have been analyzed for an immiscible polymer blend during reactive processing. A model polymer/polymer combination, hydroxy-terminated poly(ε-caprolactone)/liquid rubber with α, ω-carboxy groups, was employed. The blend was subjected to light scattering measurements, ellipsometry, and gel permeation chromatography (GPC). Size reduction of the dispersed phase during processing was followed by a systematic decrease in the correlation distance ζ and an increase in the specific interfacial area Ssp, both by the Debye-Bueche plot of light scattering profiles. Also observed was the time variation of the volume fraction of interface Vλ estimated as a product of the Ssp and the interfacial thickness by ellipsometry. The changes in ζ, Ssp, and Vλ with processing were accelerated when a coupling agent,γ-aminopropyltriethoxysilane (APS), was added. The amount of block copolymer formed in-situ in the APS-loaded system was estimated by GPC with RI and UV detectors. For the size reduction kinetics in both APS-loaded and -unloaded systems, Rittinger's law was found to be applicable.
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    Masthead (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993) 
    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.760330401
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    Optimization of the vulcanization process of rubber products (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 183-189 
    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: Selection of the optimum conditions for the vulcanization of rubber products, particularly of bulky ones, often is quite difficult. Especially in cases of high demand, it is unavoidable to destruct expensive prototypes in order to check important properties of the rubber at various locations throughout the product. Finite element calculations can be used to predict the flow of heat during the vulcanization process. By converting the total heat input at a selected location during a certain time into a so-called “effective vulcanization time” at a fixed reference temperature, it becomes possible to predict the properties of the rubber at that location. An example of such a procedure is given. However, to secure optimum conditions in this way would require repetitive (expensive) calculations. In this article a method is developed in which the vulcanization conditions are derived from the required properties of the rubber compound. The idea behind it is that optimal vulcanization is reached when at each location within the rubber product the effective vulcanization time at a selected reference temperature lies within predefined limits. The choice of the limits can be derived from the dependence of each of the properties chosen on the vulcanization time at the reference temperature.
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    Buildup and relaxation of molecular orientation in injection molding. Part I: Formulation (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 193-201 
    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 numerical simulation model for the analysis of the buildup and, the relaxation of molecular orientation in injection-molded products has been developed. The constitutive equations of the material are described using an extended version of the viscoelastic material model developed by Leonov. The volumetric responses are described using two different equations of state, the Tait equation and an equation developed by Spencer and Gilmore. A WLF-type of equation is used for the temperature and pressure dependence. Stresses calculated with the model are coupled to birefringence by means of the stress-optical rule. Birefringence, in turn, is used to characterize the molecular orientation. The model is used to investigate the influence of the processing conditions, the mold elasticity, and the pressure dependence of the material functions on the pressure and birefringence profiles. The material data used are for polystyrene, PS 678E, and are determined experimentally.
    Additional Material: 7 Ill.
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    Differential scanning calorimetry analysis of thermoset cure kinetics: Phenolic resole resin (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1665-1669 
    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 Differential Scanning Calorimetry (DSC) trace for a commercial phenolic resole resin shows two distinct peaks. Assuming that these represent two independent cure reactions results in a kinetic model of the form: \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{dx}}{{dt}} = p\kappa _1 \left({1 - x_1} \right)^{n_1} + \left({1 - p} \right)\kappa _2 \left({1 - x_2} \right)^{n_2} $$\end{document} with κi = κio exp(-Bi/T).The Arrhenius parameters were estimated from a plot of ln(β/Tp2) versus 1/Tp. The parameters, p, n1, and n2 were obtained by writing the DSC response predicted by the equation above in terms of a function which contains temperature as the only variable. \documentclass{article}\pagestyle{empty}\begin{document}$$ \dot q = q_{tot} \left[{p\kappa _1 \left({1 - \theta _1 /r_1} \right)^{r_1 - 1} + \left({1 - p} \right)\kappa _2 \left({1 - \theta _2 /2} \right)^{r_2 - 1}} \right] $$\end{document} with \documentclass{article}\pagestyle{empty}\begin{document}$ \theta _i = \left({1/\beta} \right)\int_{T_0}^T {\kappa _i dT \le r_i} $\end{document} dT ≤ ri and ri = 1/(1-ni).Fitting this equation to the DSC response measured at a scan rate of 4°C/min obtains p ≈ 0.66; n1 ≈ 0.55; n2 ≈ 2.2; B1 ≈ 8285; B2 ≈ 7480; κ1 ≈ 1. 12 × 108 s-1; κ2 ≈ 0.99 × 106 S-1.
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    An experimental and theoretical investigation of transient melt temperature during injection molding (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1674-1683 
    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 in-depth study of the effect of molding parameters on melt temperature was carried out, in which the melt temperature was measured with infrared probes. The effect of screw speed, back pressure, shot size, and polymer viscosity on melt temperature during plastication was determined. The melt temperature was not constant during injection, and was found to be as much as 44°C above the barrel temperature. The temperature rise results from viscous dissipation during plastication and adiabatic compression during injection. Measured temperatures are in qualitative agreement with a first order model of the process.
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    The use of oven heat sag to determine heat resistance in polypropylenes (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 248-252 
    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: Heat deflection is often the only test used to determine a materials ability to withstand exposure to elevated temperatures under load. This test has its limitations, simply because not all materials operate under loads of 1820 kPa (264 psi) or 455 kPa (66 psi). Consequently, heat deflection cannot always give a true indication of a materials high temperature capabilities. The automotive industry has used the heat sag test to measure the deformation of elastomeric materials during the paint curing process. The heat sag test measures the sag of a molded bar. One end of the bar is clamped while the other end is free to sag or deflect. Samples are tested over a range of temperatures to determine the failure deflection point. This study examines the correlation of the heat sag to heat deflection and dynamic mechanical analysis (DMA) on polypropylene resins and compounds and polystyrene.
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    Volumetric heating by electromagnetic energy absorption - a potential for the mass production of structural composites (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 240-247 
    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 problem of excessive heat buildup in a heat diffusion supported thermosetting process may lead, especially in the case of thick composite profiles, to compromised quality or even thermal degradation of the final product. A computer simulation of a real manufacturing process demonstrates this intrinsic weakness of the conventional manufacturing process by showing nonuniformities in the degree of cure development and a temperature inversion at the end of the processing cycle. Those nonuniformities in thermal expansion and contraction may be avoided by heating the composite uniformly throughout the whole cross section. This can be achieved with the help of electromagnetic irradiation. The electric energy absorption and, hence, conversion to heat takes place uniformly in the whole bulk of the material, regardless of the position. In effect, one can expect that the uniformly fast cured composite features superior mechanical properties over that of a composite that is conventionally processed.
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    Plane strain and plane stress analysis of fatigue crack propagation in medium density polyethylene pipe materials (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 217-226 
    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: Using the Crack Layer Theory, differences in damage formation under different stress states during fatigue crack propagation in an ethylene-butene copolymer were quantified and compared. Despite having vastly different stress states and crack propagation behaviors, arc specimens (28 mm thick) and single edge notched (SEN) specimens (2 mm thick) were shown to have the same specific enthalpy of damage, ∼300 J/g, a parameter in the Crack Layer Theory that is a measure of the material's intrinsic toughness. Damage in the SEN specimen consisted of crazing the significant material yielding; the latter damage type is associated with plane stress conditions. In the predominantly plane strain arc specimen, material yielding was minimal compared to crazing, the dominant damage form. After measuring these damage forms and applying the Crack Layer Theory, the constancy of the specific enthalpy of damage was established. Also the dissipation coefficient, β, a second parameter of the Crack Layer Theory, was shown to be a process-dependent parameter, which was inversely proportional to the lifetime of the specimen: βSEN = 4.6 × 10-5, βarc = 1.1 × 10-4, which corresponds to lifetimes of 140,000 and 30,000 cycles to failure, respectively.
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    Masthead (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993) 
    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.760330501
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    Development of high performance, waterborne coatings. Part I: Emulsification of epoxy resin (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 253-259 
    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 manufacturing process of high performance, waterborne coatings for can coating applications is developed, which includes emulsification of an epoxy resin with or without its hardener by incorporation of an acrylic resin. It becomes possible by this new process to emulsify a variety of resins with minimum effects of the surfactant acrylic resin. Thus, latitude to design formulations is widened and the performance of epoxy resin and its hardener can be fully developed.
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    Transcrystallinity phenomena in fiber-reinforced polypropylene. II: Morphology, thermal and mechanical properties relationships (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 383-391 
    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 effect of short-length carbon and Kevlar fibers on the crystallization of isotactic polypropylene (iPP) in composites prepared by compression molding has been investigated. The tendency of carbon and Kevlar fibers to nucleate the iPP during isothermal and nonisothermal crystallization has been evaluated by differential scanning calorimetry. The influence of different thermal histories used to prepare the unreinforced and reinforced samples on the crystallization parameters of iPP was examined. In addition, the tensile behavior was related to the resulting morphologies of the samples. It was observed that the crystallinity content, obtained by using different thermal treatments (slowly cooling or quenching), gives rise to different morphologies by influencing the mechanical behavior of materials as well. Moreover, the composites obtained by slow cooling seem to present a better fibber/matrix adhesion then that found in quenched samples. Possible underlying microstructures, which can explain the properties and the morphological characteristics, are also discussed.
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    Relationships in a bismaleimide resin system. Part I: Cure mechanisms (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 409-414 
    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 series of bismaleimide resin systems has been examined in order to identify the molecular features responsible for the mechanical response of these materials. A range of network structures was produced both by formulation of resins with different ratios of N,N′-bismaleimido-4,4′-diphenylmethane (BMI) and methylene dianiline (MDA), and by the use of different thermal processing cycles. Spectrographic and chromatographic techniques were used to study the reactions that occurred during the cure. Two principal reactions were confirmed: a Michael addition reaction which provides linear chain growth, and an addition reaction which produces crosslinking through the double bonds of the maleimide group. In general, curing at a lower temperature or increasing the MDA content served to favor chain extension over crosslinking, which might be expected to increase molecular mobility in the resin.
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    Processing of thermotropic liquid crystalline polymers and their blends - analysis of an in-situ LCP composite system (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 400-408 
    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: Thermotropic LCP/LCP fiber blends were prepared by a combination of meltblending and hot-drawing, using a wholly aromatic copolyester KU-9211 (also called K161 from Bayer A.G.) and an aliphatic containing LCP (liquid crystalline polymer) PET/PHB60 (from Kodak Tennessee Eastman). Morphological evidence, including scanning electron (SEM) and transmission electron microscopy (TEM), showed that the dispersed phase consisted primarily of highly oriented, 0.5 to 2 μm diameter rigid-rods of aromatic fibers imbedded in a matrix of predominantly aliphatic LCP fibrils with diameters in the range of 20 to 50 nm. An interphase of approximately 50 nm strongly bonded the two phases together. The fiber blends were characterized using dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), gas chromotography/mass spectroscopy (GC/MS), and rheological measurements. It appears that the processing conditions employed for melt blending had caused PET/PHB60 to undergo chain scission, thereby creating chemical interactions between the two LCP components during the melt blending process. Differential scanning calorimetry (DSC) thermograms as well as nuclear magnetic resonance (NMR) spectra of the extracted fraction from the mixture of 30 wt% K161/70 wt% PET(PHB60) confirmed the chemical interaction between the two thermotropic liquid crystalline polymers.
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    A pulse rheometer for reacting foams (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 426-430 
    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 foam rheometer has been developed based on the impulse theory of linear viscoelasticity. The rheometer is a large-volume parallel-plate device which operates under gap-loaded conditions, and is designed as an add-on fixture for the Materials Testing System Model 312. The rheometer provides characterization data of the pre-gel (via the zero-shear viscosity) or the post-gel (via the equilibrium modulus) properties of a foaming cellular polymer with a precision of better than ± 15%.
    Additional Material: 7 Ill.
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    Mechanical and rheological properties of poly(butadiene-acrylonitrile) rubber compounds reinforced with cellulosic material (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 443-447 
    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 usefulness of waste (mainly cellulosic) materials as a reinforcement for acrylonitrile-butadiene rubber (NBR) compounds is shown in this work. The materials tested are: henequen, pine, coconut, sugarcane husks, lignin, and wood sawdust. Their performance is compared with that of commercial reinforcement materials (santocel and solka), using the same copolymer composition without reinforcement as a reference compound. Uniform particle size is achieved by milling and screening. For some of the materials, 6 mm fibers and polymerfiber coupling agent are also tested. Reinforced copolymer formulations are prepared by milling. Optimum curing times are determined with a torsion rheometer. Mechanical and rheological tests (stress-strain behavior, tear resistance, hardness, interfacial strength, storage modulus, and loss tangent), show promising results for some materials, especially when looking for a reinforced product with low dissipation energy.
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    A mixing model for multicomponent reactions in twin screw extruders applied to the polymerization of urethanes (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 457-466 
    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 understand the performance of multicomponent reactions in twin screw extruders the mixing mechanism in the extruder had to be understood. Therefore, two new relevant mixing parameters are defined; the mixing efficiency, which is the average number of passages of material through a high shear region; and the mixing deficiency, which is the fraction of material that does not pass through a high shear region. With these parameters an analysis can be made of the mixing circumstances in the extruder. The new model was applied to the polymerization of urethanes in a counter-rotating twin screw extruder. The results agreed very well with the theoretical expectations.
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    The grafting of maleic anhydride on high density polyethylene in an extruder (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 467-474 
    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 grafting of maleic anhydride (MAH) on high density polyethylene in a counter-rotating twin screw extruder has been studied. As the reaction kinetics appear to be affected by mass transfer, good micro mixing in the extruder is important. Due to the competing mechanisms of increasing mixing and decreasing residence times at increasing screw speed, and due to the complicated reaction scheme, various non-linearities exist that are prohibitive for simple optimization rules. The interaction diagram presented in this paper for a twin screw extruder as a MAH grafting reactor can be used for better understanding of the influence of the extruder parameters on the reaction process.
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    Comparison of “all trans” enzymatically prepared unsaturated polyesters with chemically synthesized and industrial polyesters (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 311-315 
    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 unsaturated polyesters (UP) by high-temperature polycondensation is accompanied by isomerization of the double bond from the cis to the trans configuration. The presence of the trans double bonds facilitates crosslinking and may have an important influence on rheological and mechanical properties of the UP and the cured end product. All-trans polyesters are not available on the market. A study of “all-trans” low-temperature polycondensation based on chemical and enzymatic lipase catalysis was recently reported. This paper presents the characteristics of lipase-synthesized UP vs. general-purpose UP, as obtained by X-ray, differential scanning calorimetry (DSC), and other methods. In contrast to the commercial amorphous UP, crystallinity was found in the “alltrans” enzymatically and chemically synthesized UP. The crystallinity of the enzymatically and chemically synthesized UP. The crystallinity of the enzymatically synthesized UP was confirmed by higher values of elasticity. DSC analyses complemented the results obtained by other methodologies.
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    URL: http://dx.doi.org/10.1002/pen.760330511
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    Molecular structure, morphology, and antioxidant- consumption in polybutene-1 pipes in hot-water applications (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 303-310 
    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: Pipes of isotactic polybutene-1 (PB) have been exposed to internal water and external air in pressure tests at 105°C. The pipes exposed to different internal pressures exhibited different failure mechanisms, referred to as stages I, II, and III. Samples taken from these pipes have been analyzed by infrared (IR) spectroscopy, wide-angle X-ray scattering (WAXS), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). IR spectroscopy and WAXS confirmed that thermal oxidation of the amorphous part of the polymer accompanied the onset of stage III. Thermal oxidation led to extensive molar mass reduction and to a significant increase in mass crystallinity and melting peak temperature. Extensive and visible degradation in pipes failing according to stage III was confined to so-called “oxidation spots.” The latter were first formed at the outer wall and propagated inwards, finally constituting approximately 50% of the wall thickness. The antioxidant concentration profiles obtained by DSC were always symmetrical and were successfully adapted to a previously developed model. It was shown that migration of the antioxidant was the dominant loss mechanism, that the diffusion coefficient was constant through the pipe wall, and that the evaporative loss to the external air was marginally greater than the loss to the internal water phase. Chemical consumption of the antioxidant was found to be negligible.
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    Analysis of the coupling between the apparent time scale of thermal degradation and sample sizeA portion of the work was presented at IUPAC'90, Montreal. (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 317-321 
    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: Sample size sensitivity of thermal gravimetric analysis (TGA) presents a serious handicap in the obtaining of reliable thermal stability data for high-temperature applications. For example, predictions of the apparent time for degradation during an isothermal experiment based on the results obtained using a 10 μm thick specimen can be off by an order of magnitude when applied to a product with a thickness of 10 cm. To address this effect, TGA experiments studying the thermal degradation of poly(methyl methacrylate) were conducted. Analysis of the experimental data resulted in the development of a relationship between the apparent time scale of the thermal degradation and the specimen thickness. Origins of the new dependence were traced to the change of the diffusivity resulting from material volatilization. Implications of the coupling between these two events for the analysis of thermal stability for new polymeric materials are discussed, and required changes in the current methodology are outlined.
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    Measurement and correlation of mutual diffusion coefficients for styrene-butadiene rubber(SBR)-n-nonane systems (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 322-327 
    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 mutual diffusion coefficients for styrene-butadiene rubber(SBR)-n-nonane systems were measured using a sorption apparatus with a quartz spring at 100 and 130°C for mass fractions of n-nonane ranging from 0 to 0.16. The mutual diffusion coefficients were correlated with good agreement by the free-volume theory.
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    On the tensile testing of high modulus polymers and the compliance correction (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 328-333 
    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 application of a method to determine and correct for the influence of non-specimen extension in tensile testing is reviewed and demonstrated using two different thermotropic liquid crystalline polymers. In the tensile testing of high modulus polymer extrudate, where the amount of specimen extension is inferred from the crosshead travel, the error associated with system compliance can be significant and parameters such as modulus and elongation will be in error. The need to apply the correction depends on the magnitude of the product of the sample modulus and cross-sectional area, divided by the test gage length, relative to the system compliance value. Its application is not necessarily restricted to high modulus materials, and can be extended to samples of larger cross-sectional area and lower modulus. Guidance to assist in the choice of a suitable gage length to avoid compliance correction and a method to quantify the error contribution is presented.
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    CO2 laser welding of polymers (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 582-585 
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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: Deep penetration welding of polymers can be carried out at high speed with relatively low laser power. This results from an efficient coupling CO2 laser radiation to polymers that leads to volume heating. A brief review of energy coupling and heat transfer effects in polymers under CO2 laser welding conditions is given. Some examples of low power (10 to 100 watt) CO2 welding of polypropylene and polyethylene at depths of up to 1.5 cm are discussed.
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    URL: http://dx.doi.org/10.1002/pen.760320903
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    Fatigue strength of vibration welded thermoplastic butt joints (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 593-599 
    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: Fatigue data are presented for the strengths of 120-Hz vibration-welded butt joints of four resins: the three amorphous polymers polycarbonate (PC), polyetherimide (PEI), and modified polyphenylene oxide; and the semicrystalline polymer poly(butylene terephthalate). Data are also presented for the fatigue strength of 250-Hz vibration welds of the high-temperature polymer PEI. For all the welds, fatigue strength was evaluated through 10-Hz, tension-tension, load-controlled tests at an R value (ratio of minimum stress) of 0.1. Surprisingly, for all the stress levels studied, none of the PC test specimens failed at the welds, indicating that the fatigue strength of PC welds equals that of the base resin. This is not true of the other three resins, except at relatively low stress levels. For each of the four resins, macrographs are used to highlight the differences between the failure surfaces of monolithic specimens and specimens that failed at the welds.
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    Ultrasonic welding using tie-layer materials. part II: Factors affecting the lap-shear strength of ultrasonic welds (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 612-619 
    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 influence of tie-layer Melt Flow Index on the lap-shear strength of ultrasonic welds in oriented polypropylene (OPP) has been evaluated. The tie-layer Melt Flow Index was varied from 0.03 dg/min to 2600 dg/min; the highest lap-shear strength properties were obtained using tie-layers that had melt flow index values between 30 and 100 dg/min. When using low Melt Flow Index tie-layers, hot spot formation and concomitant changes in fusion zone and heat-affected-zone dimensions produced stress concentrations that promoted failure in oriented polypropylene material away from the bondline region. When very high Melt Flow Index (2600 dg/min) tie-layers were used, the mode of failure during lap-shear testing was a mix of cohesive, in oriented polypropylene, and adhesive failure. The molecular weight of material at the bondline was not markedly affected by the thermal cycle produced during ultrasonic welding. Only the flash ejected when using low Melt Flow Index tie-layers exhibited any evidence of degradation; it is suggested that the ejected flash may have been degraded because of a combination of thermal, cavitation, and thermo-oxidative processes.
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    Experimental characterization of processing-performance relationships of resistance welded graphite/polyetheretherketone composite joints (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 620-631 
    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 study to investigate fusion bonding (welding) of AS4 graphite/polyetheretherketone (PEEK) thermoplastic composites is presented. Processing studies are conducted for resistance welding preconsolidated AS4/PEEK laminates in both unidirectional and quasi-isotropic configurations using PEEK and polyetherimide (PEI) film at the joint interface. All bonding was done under a constant displacement process. The influence of processing time, initially applied consolidation pressure, and the rate of heat generation on weld performance is examined through lap shear and Mode I interlaminar fracture toughness testing. A rapid increase in strength with processing time that asymptotically approaches the compression molded baseline is measured. Weld times for quasi-isotropic lap shear coupons are significantly shorter than those with a unidirectional lay-up. Variation of the initially applied consolidation pressure is shown to have little influence on the lap shear strength of PEEK film welded lap joints. A discussion of the mechanisms allowing void formation during the welding process is given. Bond strength test results are correlated with ultrasonic C-scans of the weld regions.
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    Resin flow through fiber beds during composite manufacturing processes. Part I: Review of newtonian flow through fiber beds (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 221-230 
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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: A critical part of any master model used to simulate or control a composite material manufacturing process is the description of resin flow through the fiber bed. We present here a review of both theoretical and experimental studies of fluid flow through porous media, including fiber beds. For the practical porosity range of interest in continuous fiber composites processing (0.3〈 ∊ 〈 0.6), the permeability cannot be accurately described using the Blake-Kozeny-Carman equation, even though the flow is Newtonian at very low Reynold's number. For aligned fiber situations, the Kozeny constant, k, deviates radically from theory, depends on bed nonuniformities, and is only constant over very narrow porosity ranges. Thus, one cannot experimentally determine k at high porosities and use this value to describe low porosity situations. Theoretical attempts, based on perfectly spaced and aligned arrays of cylinders, adequately describe the transverse permeability of ideal fiber beds in the high porosity range, but do not succeed at porosities below 0.6. For axial flow through aligned fiber beds, the theory yields permeabilities much lower than are experimentally observed throughout the entire porosity range. For randomly arranged fibers, random cylinder theory also predicts permeabilities that are significantly lower than are measured.
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    Effects of thermal modification on the structural properties of thermotropic liquid crystalline copolyester and phenoxy resin blends (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 267-272 
    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 effects of thermal modification on the structural properties were studied for a poly(ethylene terephthalate-co-p-hydroxybenzoic acid) liquid crystal bended with phenoxy resin. Poor miscibility and phase separation between the blend components are observed by the temperature dependence of dynamic mechanical properties of sample molded at 260°C, over the composition range studied. The miscibility of the blends is increased by molding at 280°C, and the blends molded by increasing the processing time show a dynamic mechanical transition to a homogeneous blend. These changes are the result of an interchange reaction between the blend components. A rubbery modulus has been observed for such blends. This implies the formation of cross-linked structures that accompany the interchange reactions.
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    Resin flow through fiber beds during composite manufacturing processes. Part II: Numerical and experimental studies of newtonian flow through ideal and actual fiber beds (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 231-239 
    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: Proper description of the resin flow through fibrous media is an important input to the modeling of composite manufacturing processes. Based on our conclusions in a recent review of pertinent literature (see Part I, this issue), Newtonian flow through ideal cylinder arrangements has been analyzed and measured. The analytical and numerical solutions agreed well with both our own experimental observation and those of others. Experiments with actual carbon fiber beds revealed significant deviations from ideal bed behavior. These deviations include dependence of the permeability on the nature of the permeant and the applied pressure difference, both of which make questionable the use of the Blake-Kozeny-Carman (BKC) equation to describe flow in real carbon fiber beds. Experiments that simulate the autoclave process by featuring combined permeation and consolidation of fiber beds have yielded additional dependencies of the permeability on process characteristics, such as the consolidation load and the original resin-rich areas within the fiber beds.
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    Numerical prediction of fiber orientation in injection molding (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 254-266 
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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: We develop a numerical method for calculating fiber orientation in the midsurface of a molded part of small thickness. Two-dimensional fiber orientation is predicted on the basis of either Jeffery's equation or a constitutive equation for the orientation tensor. The calculation is fully transient; it is performed on a time-dependent flow domain. The method is based on finite elements. Updated finite element meshes are generated at every instant of filling and allow one to perform an accurate calculation of the orientation even along the boundary of the flow domain. The method is applied to several examples in plane and three-dimensional geometries.
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    URL: http://dx.doi.org/10.1002/pen.760320405
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    Stereological measurement and error estimates for three-dimensional fiber orientation (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 240-253 
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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: A method is presented for measuring three-dimensional fiber orientation in fiber-reinforced polymers and placing confidence limits on the results. The orientations of individual fibers are determined from the elliptical intersections between the cylindrical fibers and a polished section. This can be done using either manual digitization or automated image analysis. Volume averages for the sample are computed using an orientation-dependent weighting function that corrects for the bias of an area-based sample. Equations are developed for nonuniform fiber lengths, using both number-average and weight-average measures of orientation. Sources of systematic, measurement, and sampling error are discussed and equations for sampling error and the propagation of measurement error are derived. The results use a second-rank tensor to characterize fiber orientation, but the error analysis can be applied to any type of orientation parameter. We implement the technique using manual digitization of optical micrographs. Our implementation accurately measures samples with known orientation, and produces identical results from two perpendicular sections of a glass fiber/nylon injection-molded sample.
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    Impact resistance performances of polyamide 6 blended with different rubber phases (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 273-279 
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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: We have studied the impact strength, by Charpy and Izod tests, of blends of polyamide 6 with different rubbers, 10 wt% of each, or rubbers and glass fibers (8.5 wt% and 15 wt% respectively). The rubbers are from three different families: (i) a nonreactive cross-linked terpolymer, methyl methacrylate/butadiene/styrene (17/64.5/18.5); (ii) two block copolymers compatible with the matrix, poly(tetramethylene glycol)/polamide 12 (70/30 or 34/66); and (iii) two polymers containing reactive functionality, a terpolymer ethylene/ethyl acrylate/maleic anhydride (68/30.5/1.5) and a copolymer ethylene/acrylic acid (90/10). The classification of additives in regard to improved impact depends on the procedure used for the impact strength measurement, particularly on whether the samples are notched or unnotched. The results are discussed in relation to the dimensions and the adhesion of the rubber particles. The level of adhesion has been estimated from observations in scanning electron microscopy of cavities due to pullout nodules and of nonextracted rubber after treatment in boiling xylene. Strong variations in the morphologies are found, depending on the chemical nature of the rubber. The crystalline state of the polyamide in the blends has also been evaluated from differential scanning calorimetry.
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    The impact performance of thermoplastic sheet composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 287-297 
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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: Sheet composites of polypropylene and poly(ethylene terephthalate) were produced by melt consolidation of alternating layers of polymer films and random glass fiber mats. The composites had a nominal glass content of 50 wt% (∼30 vol%). The sheets were stamped into a complex part from which test specimens were machined, and mechanical properties determined. Flexural strengths as high as 159 MPa were recorded for polypropylene composites and 313 MPa for poly(ethylene terephthalate) composites. The flexural modulus of the polypropylene composites reached 9.1 MPa, whereas the modulus of the stiffest poly(ethylene terephthalate) composite was 15 GPa. The impact properties of the composites were equally high. Polypropylene composites absorbed up to 257 J/cm during an instrumented falling dart impact test. Poly(ethylene terephthalate) composites absorbed as much as 116 J/cm in the same test.
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    Masthead (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992) 
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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.760320501
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    Interpretation of fiber fragmentation in carbon/epoxy single fiber composites: Possible fiber pre-tension effects (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 298-304 
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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 fiber straightening pre-tension applied during the sample preparation of single fiber composites is suggested here to significantly affect the number of fragments as well as the value of the Kelly-Tyson interface shear strength obtained from single filament composite tests. This implies that fragmentation tests performed under seemingly identical conditions, but in which the fiber pre-tension is not accurately controlled during sample preparation, might yield widely differing experimental results. We present and discuss a new set of experimental results dealing with fiber pre-tension effects in carbon/epoxy single fiber composites.
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    The effects of transcrystalline interphase in advanced polymer compositesThis paper has been presented in part or in full at the Materials Research Society Symposium N, Boston, November 1989; the Third International Conference on Composite Interfaces, Cleveland, May 1990; and the Textile Institute World Conference, Dundee, Scotland, November 1990. (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 280-286 
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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: Surface-induced transcrystallization in fibers has been reported in some advanced polymer composites. It is believed that transcrystalline interphase may affect stress transfer efficiency between the reinforcing fiber and the matrix. In this study, attempts were made to examine the effects of transcrystallinity on composite performance, particularly on fiber-matrix interfacial bond strength, and to investigate possible attributes of transcrystallization. Three polymer resins, poly(etherketoneketone) (PEKK), poly(etheretherketone) (PEEK), and poly(phenylenesulfide) (PPS), and four types of fiber, polyacrylonitrile (PAN)-based AU-4 (untreated AS-4) carbon, pitch-based carbon, poly (p-phenylene terephthalamide) (PPDT) aramid, and E-glass were used. It was found that PPDT aramid and pitch-based carbon fibers induce a transcrystalline interphase in all three polymers because of an epitaxial effect. Under certain conditions, transcrystallization was also observed in PAN-based carbon and E-glass fibers, which may be partially attributed to the thermal conductivity mismatch between the fiber and the matrix. Plasma treatment on fiber surface showed a negligible effect on inducing transcrystallization, whereas solution-coating of PPDT on the fiber surface showed a positive effect. The Microdebonding test, which measures the interfacial bond strength between the fiber and the matrix, consistently showed more than 40% increments for various single filament systems with transcrystalline interphase versus without. However, the effects of transcrystallinity on the interfacial bond strength appeared to decrease as the fiber content increased in composites.
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    Fabrication and electrical properties of ceramic superconductor/polymer composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 305-309 
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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: Superconductor/polymer composites were prepared by mixing powders representing the Y-Ba-Cu-O and Bi(Pb)-Sr-Ca-Cu-O systems with high-density polyethylene. Their electrical resistivities were measured as a function of temperature. By controlling the powder preparation techniques, it was possible to fabricate composites with superconductive transition to zero resistivity in the Bi(Pb)-Sr-Ca-Cu-O system. These composites can be fabricated in certain desired shapes.
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    Strength of glass-filled modified polyphenylene oxide vibration-welded butt joints (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 511-518 
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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 strengths of glass-filled modified polyphenylene oxide (GF-MPPO) welds relative to the strengths of GF-MPPO are shown to depend on specimen thickness. (Modified polyphenylene oxide is a blend of poly (2,6-dimethyl-1,4-phenylene ether) and high-impact polystyrene.) Relative strengths on the order of 70 and 87 percent can be achieved in 6.1 and 3.18-mm-thick specimens, respectively. Welds of GF-MPPO to modified polyphenylene oxide (MPPO) can easily attain the strength of MPPO, the weaker of the two materials. In contrast to MPPO, in which weld strength decreases with increased weld pressure, the strengths of GF-MPPO to GF-MPPO welds and GF-MPPO to MPPO welds, are not affected by weld pressure.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310707
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