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  • Chemical Engineering  (1,281)
  • Wiley-Blackwell  (1,281)
  • Annual Reviews
  • 2005-2009
  • 1990-1994  (1,281)
  • 1993  (638)
  • 1991  (643)
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  • Wiley-Blackwell  (1,281)
  • Annual Reviews
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  • 2005-2009
  • 1990-1994  (1,281)
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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1057-1063 
    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.
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  • 2
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    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
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  • 3
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1071-1078 
    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.
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  • 4
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1064-1070 
    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.
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  • 5
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1086-1093 
    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.
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  • 6
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1081-1085 
    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.
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  • 7
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1094-1100 
    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.
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  • 8
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    Polymer Engineering and Science 31 (1991), S. 1101-1107 
    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.
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  • 9
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1108-1112 
    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.
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  • 10
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    Polymer Engineering and Science 31 (1991), S. 1113-1116 
    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.
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  • 11
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    Polymer Engineering and Science 31 (1991), S. 1137-1148 
    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.
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  • 12
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1130-1136 
    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.
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  • 13
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991) 
    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
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  • 14
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    Polymer Engineering and Science 31 (1991), S. 1149-1156 
    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.
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  • 15
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    Polymer Engineering and Science 31 (1991), S. 1157-1163 
    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.
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  • 16
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    Polymer Engineering and Science 31 (1991), S. 1165-1171 
    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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  • 17
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    Polymer Engineering and Science 31 (1991), S. 1176-1181 
    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.
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  • 18
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    Polymer Engineering and Science 31 (1991), S. 1182-1188 
    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.
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  • 19
    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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  • 20
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    Polymer Engineering and Science 31 (1991), S. 1194-1199 
    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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  • 21
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    Polymer Engineering and Science 31 (1991), S. 1200-1206 
    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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  • 22
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    Polymer Engineering and Science 31 (1991), S. 1215-1221 
    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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  • 23
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    Polymer Engineering and Science 31 (1991), S. 1233-1239 
    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.
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  • 24
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    Polymer Engineering and Science 31 (1991), S. 1310-1315 
    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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  • 25
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    Polymer Engineering and Science 31 (1991), S. 1316-1329 
    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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  • 26
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    Polymer Engineering and Science 31 (1991), S. 1351-1357 
    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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  • 27
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    Polymer Engineering and Science 31 (1991), S. 1372-1385 
    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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  • 28
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    Polymer Engineering and Science 31 (1991), S. 1386-1392 
    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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  • 29
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    Polymer Engineering and Science 31 (1991), S. 1393-1399 
    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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  • 30
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    Polymer Engineering and Science 31 (1991), S. 1417-1425 
    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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    Polymer Engineering and Science 31 (1991), S. 1426-1433 
    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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  • 32
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    Polymer Engineering and Science 31 (1991), S. 1450-1460 
    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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    Polymer Engineering and Science 31 (1991), S. 1441-1449 
    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.
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  • 34
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    Polymer Engineering and Science 31 (1991), S. 1476-1482 
    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.
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  • 35
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    Polymer Engineering and Science 31 (1991), S. 1483-1492 
    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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    Polymer Engineering and Science 31 (1991) 
    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
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  • 37
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    Polymer Engineering and Science 31 (1991), S. 1509-1519 
    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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  • 38
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    Polymer Engineering and Science 33 (1993), S. 70-74 
    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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  • 39
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    Polymer Engineering and Science 33 (1993), S. 83-91 
    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.
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    Polymer Engineering and Science 33 (1993), S. 75-82 
    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.
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    Polymer Engineering and Science 33 (1993), S. 92-96 
    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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  • 42
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    Polymer Engineering and Science 33 (1993), S. 97-99 
    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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    Polymer Engineering and Science 33 (1993), S. 100-107 
    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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  • 44
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    Polymer Engineering and Science 33 (1993), S. 115-121 
    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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    Polymer Engineering and Science 33 (1993) 
    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
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    Polymer Engineering and Science 33 (1993), S. 122-124 
    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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  • 47
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    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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    Polymer Engineering and Science 33 (1993), S. 125-131 
    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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  • 49
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    Polymer Engineering and Science 33 (1993), S. 132-139 
    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.
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    Polymer Engineering and Science 31 (1991) 
    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
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  • 51
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    Polymer Engineering and Science 31 (1991), S. 1610-1617 
    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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    Polymer Engineering and Science 31 (1991), S. 1618-1626 
    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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  • 53
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    Polymer Engineering and Science 33 (1993), S. 156-165 
    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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    Polymer Engineering and Science 33 (1993), S. 175-182 
    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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    Polymer Engineering and Science 33 (1993) 
    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
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    Polymer Engineering and Science 33 (1993), S. 183-189 
    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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    Polymer Engineering and Science 33 (1993), S. 193-201 
    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.
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    Polymer Engineering and Science 31 (1991), S. 1665-1669 
    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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    Polymer Engineering and Science 31 (1991), S. 1674-1683 
    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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    Polymer Engineering and Science 33 (1993), S. 248-252 
    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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    Polymer Engineering and Science 33 (1993), S. 240-247 
    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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    Polymer Engineering and Science 33 (1993), S. 217-226 
    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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    Polymer Engineering and Science 33 (1993) 
    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
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    Polymer Engineering and Science 33 (1993), S. 253-259 
    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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    Polymer Engineering and Science 33 (1993), S. 311-315 
    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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    Polymer Engineering and Science 33 (1993), S. 303-310 
    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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    Polymer Engineering and Science 33 (1993), S. 317-321 
    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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    Polymer Engineering and Science 33 (1993), S. 322-327 
    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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    Polymer Engineering and Science 33 (1993), S. 328-333 
    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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    Polymer Engineering and Science 31 (1991), S. 511-518 
    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.
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    Polymer Engineering and Science 31 (1991), S. 519-525 
    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 hot-tool welding process is commonly used for welding plastics, but high seam quality can be obtained only by optimizing weld parameters. Because of demand for better quality, the importance of quality control is increasing. At present, quality control is mainly performed by inspecting the end product, resulting in high scrap rates. An effective quality control system must therefore be able to recognize errors as they occur during the manufacturing process. For this, an FMEA (Failure Mode Effect Analysis) should be performed prior to mass production, and statistical quality control should be implemented during and after the process. This paper describes a quality control system for computer controlled hot-tool welding that is based on an understanding of the physics of the process.
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    Polymer Engineering and Science 31 (1991), S. 526-532 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper describes a process that facilitates fusion bonding of thermoplastic composite components without the need for complex fixtures and without disrupting the fiber alignment in the component laminates. The dual polymer bonding process, Thermabond, requires that an interlayer polymer be fused to the surface of each laminate prior to bonding. The characteristics of the interlayer polymer allow for joining of the components at a temperature below the softening/melting point of the reinforced polymer in the composite laminates. This leads to significant processing advantages without significant loss in mechanical performance. Discussions of resin compatibility, the effect of process conditions on mechanical performance, and the application of the APC-2/PEI Thermabond system to various structural components are included.
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    Polymer Engineering and Science 33 (1993), S. 543-548 
    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 static shear strength and static friction of three thermoplastics have been investigated for the case of contact between a bulk plastic sample and a very smooth metallic plate. The minimum tangential force required to shear the interfacial adhesion bonds between the two surfaces was measured and defined as the adhesion component of friction Fa. Experimental results showed that Fa is large when the surface energy is high or the interfacial energy is small and that a correlation may exist between this force and the work of adhesion evaluated from Dupré equation. The real area of contact Ar was also measured using an optical device designed to handle samples and experimental conditions similar to the static friction tests. It was found that Ar is proportional to Pa0.9 where Pa is the apparent pressure of contact and an increase of Fa with Pr was observed. The static shear strength τ has been evaluated as the ratio Fa/Ar, and its relationships with the real contact pressure P approximated by linear functions. It was concluded that τ increases at high P, although it has not been verified for ultra-high-molecular-weight polyethylene. An attempt has been made to explain the observed break in the data. The results indicated that (τ/τb) = κ′(τa/Pa) where b refers to bulk, a to apparent values, and κ′ is a proportionality constant that depends on the plastic material.
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    Polymer Engineering and Science 33 (1993), S. 614-621 
    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 glass transition temperatures in bismaleimide-based resins were investigated using different stoichiometric ratios of 1, 1′-(methylenedi-4, 1-phenylene)bismaleimide (BMI) and 4, 4′-methylenedianiline (MDA). The resin cure involves a low temperature primary amine addition to the maleimide double bonds and a high temperature homopolymerization of the maleimide double bonds. The network topology and the glass transition temperature changes with resin composition and curing conditions were determined using differential scanning calorimetry (DSC). An empirical model was used to relate the glass transition temperature to the extents of the amine addition and the homopolymerization reactions in 1:1 and 2:1 BMI:MDA resins. The changes in thermal properties with resin post-cure were also examined.
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  • 75
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    Polymer Engineering and Science 33 (1993), S. 640-644 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dynamic mechanical properties, tensile properties, and scanning electron microscopy of blends of poly(methyl methacrylate) and polycarbonate were investigated after phase separation above their cloud point temperature by annealing in a hot press. The dynamic mechanical properties show that phase separation proceeds more distinctly for the blends annealed at higher temperature and for longer time. The scanning electron micrographs show that the morphology of phase separated blends varies with the conditions of heat treatment. The tensile properties of phase separated blends deteriorate on account of the coarsening of the brittle dispersed phase over the optimum size and the occurrence of voiding during the heat treatment.
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  • 76
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    Polymer Engineering and Science 33 (1993), S. 665-674 
    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 packing stage starts at the end of mold filling. During this stage, additional material is forced into the mold to compensate for the shrinkage during subse-quent cooling. Underpacking results in molded parts with dimensional variation. Overpacking causes flash at the parting lines, stick during ejection, and excess residual stresses resulting in warpage. The packing stage is thus extremely important in the determination of the final quality of the product. Despite its importance, analysis of the packing stage has been relatively ignored, particularly the viscoelastic effect. In this work, the analysis of the isothermal packing stage is presented for a Maxwell fluid. A set of governing equations is derived for a two-dimensional mold and solved using the Galerkin finite element method. In addition to the distribution of velocity and pressure, the model predicts the stresses in the planar direction, which could be used for subsequent calculation of the residual stresses.
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  • 77
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    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: Non-isothermal crystallization growth rates of nucleated and non-nucleated isotactic polypropylene (iPP) in dotriacontane were determined experimentally by thermal optical microscopy. Adipic acid was used as the nucleating agent. The non-isothermal growth rates of the nucleated and non-nucleated systems were compared with experimentally determined isothermal growth rates. The Lauritzen and Hoffman growth rate equation, originally developed for isothermal crystallization, was modified to describe the non-isothermal growth. The modified Lauritzen-Hoffman equation was used to predict isothermal growth rates from non-isothermal crystallization for the nucleated and non-nucleated polymer-diluent mixtures. This study is the first to deal with polymer-diluent-nucleating agent systems vital to membrane production.
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  • 78
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    Polymer Engineering and Science 33 (1993), S. 564-572 
    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 Dow process for producing perfluorinated ionomeric membranes includes several emulsion copolymerizations involving gaseous tetrafluoroethylene and a second liquid phase monomer. The choice of the organic phase monomer depends on the desired product. The emulsion copolymerization reactor model was developed by extending the Smith-Ewart-Gardon theory for emulsion polymerization processes. Population balance techniques and Flory-Huggins solution theory were applied. The resulting coupled partial differential equations were solved using the method of characteristics. The reactor model, with minimal adjustable parameters, predicts most polymerization results, including molecular weight, reaction rates in the three process stages, latex particle size, polymer composition, and the composition drift as a function of reaction time. The analysis and reactor model is used in the manufacturing process to set process conditions to obtain the desired properties in the polymer product.
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  • 79
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    Polymer Engineering and Science 33 (1993), S. 598-606 
    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 phase separation behavior of unsaturated polyester (UPE)-polyurethane (PU) interpenetrating polymer networks (IPNs) was investigated by light scattering measurements during simultaneous polymerization. The scattered light intensity change with time showed the formation of the dispersed domains, and the average domain correlation length could be calculated from the angle of maximum scattering intensify. It was noted that the dominant phase separation process was spinodal decomposition due to fast reaction. The morphology observed by the transmission electron micrographs for various process conditions showed similar results as obtained from the light scattering experiment.
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  • 80
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    Polymer Engineering and Science 33 (1993), S. 754-763 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of a thermotropic liquid crystalline polymer (LCP), Vectra A900, and a thermoplastic elastomer, Kraton G1650, were made on a single screw extruder. During extrusion, fibers of the LCP are formed under influence of shearing and elongating forces. The stiffness and tensile strength of the elastomer are greatly improved by the addition of the LCP. The modulus of elasticity of blends containing up to 20% LCP can be described well with the Halpin-Tsai equation. Differential scanning calorimetry and dynamic mechanical thermal analysis (DMTA) measurements show that the polymers are immiscible, but the DMTA results show a shift of the glass transition temperature of the elastomeric block of the Kraton polymer. This shift may be attributed to a layer of elastomer adsorbed on the LCP particles.
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  • 81
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    Polymer Engineering and Science 33 (1993), S. 772-780 
    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 morphology developing during the spinodal decomposition process of polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends was successfully controlled by photo-crosslink reactions between PS chains. The crosslink reaction was carried out by taking advantage of the photodimerization of anthracene moieties that are labeled on PS chains. Effects of photo-crosslinks on the morphology induced by temperature jumps (T-jump) from the one-phase region into the spinodal region were examined under several experimental conditions such as T-jump depths and irradiation times. It was found that the concentration fluctuations developing during the spinodal decomposition process were efficiently frozen upon irradiation using a XeF excimer laser as well as a mercury (Hg) lamp. Furthermore, these ordered structures are quite stable upon annealing. These results demonstrate that the morphology developing during the spinodal decomposition process can be well controlled by easily accessible light sources such as high pressure mercury lamps. Thus the photo-crosslink reaction described in this work can provide the basis for a potential technique to design multiphase polymer materials with controllable ordered structures.
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  • 82
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    Polymer Engineering and Science 33 (1993), S. 865-876 
    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 review presents a general picture of suspension, dispersion, and interfacial polycondensation processes employed for the preparation of beaded resins, dry powders, and high solid dispersions. The polymer systems covered include polyamides, polyesters, polycarbonates, polyurethanes, and phenol-formaldehyde and urea-formaldehyde resins. Basic features of heterogeneous polycondensation processes are outlined, and different mechanisms of particle formation in suspension, dispersion, and interfacial polycondensation are discussed. Effects of manufacturing parameters such as feed ratio, droplet/particle stabilizer, and stirrer speed on product characteristics are also briefly covered.
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    Polymer Engineering and Science 33 (1993), S. 901-906 
    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: Polyimide blends consisting of pyromellitic dianhydride/4,4′-oxydianiline (PMDA/ODA) and biphenyl-tetracarboxylic dianhydride/p-phenylene diamine (BPDA/PDA) show a distinct glass transition behavior at temperatures lower than each component does. Disruption of molecular packing by blending of polymers having dissimilar interaction sites leads to a significant increase in molecular mobility at much lower temperatures. This is examined by laminating two pieces of film cast from the blend and measuring the adhesive strength at the interface. A strong adhesion, 11.5 N/cm (6.6 lbf/in) by 180° peel test, was achieved indicating interpenetration of polyimide molecules. It was also found that the polyimide blends can be converted into highly ordered states by mechanical deformation of the blends above their glass transition temperatures (Tgs).
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    Polymer Engineering and Science 33 (1993), S. 913-922 
    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: Semi-interpenetrating networks have been produced from castor oil and poly(ethylene terephthalate) (PET). Bond interchange between PET and castor oil plays a major role in the development of initial miscibility, also affecting morphology and chemical structure. Microheterogeneous morphology is developed for materials of intermediate composition, which have much greater toughness than the polymers from which they were made.
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    Polymer Engineering and Science 33 (1993) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Polymer Engineering and Science 33 (1993), S. 989-995 
    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 twin screw extrusion and stampable sheeting processes, we have investigated the application of reactive processing technology to fiber-reinforced stampable sheet made of an unsaturated polyester (UP) alloy with high toughness. As a result, we obtained a stampable sheet composed of a UP/nitrile butadiene rubber (NBR) polymer alloy matrix and glass fiber mats with physical properties equivalent to those of polypropylene (PP) stampable sheet, and moreover, with higher heat resistance than PP.
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    Polymer Engineering and Science 33 (1993) 
    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
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  • 88
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    Polymer Engineering and Science 33 (1993), S. 1022-1026 
    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: Steady flow behavior of bulk liquid crystals and polymeric liquid crystals are summarized into a three region flow curve. Changes in the internal structure during deformation and flow were investigated by rheo-optical methods. Two different optical geometries were used. In one method, a light beam passed through perpendicular to the shear plate, and in the other method a light beam passed perpendicular to the edge of the lamina flow. The results indicate that the details of the internal texture do not necessarily appear in the rheological properties, such as viscosity, and that the molecular orientation mechanism under shear force is fundamentally different in a liquid crystal of rod-like molecules and a suspended solution of rod-like molecules. In the isotropic solution, the rod-like molecules float or are suspended in a solvent and are oriented by the flow field of the solvent fluid. However, in a liquid crystal, the torque propagates directly on the individual rod-like molecules, affecting their orientation. They flow as if it were a plastic solid.
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    Polymer Engineering and Science 33 (1993), S. 1042-1048 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polybenzimidazole (PBI) and polysulfone (PS) do not form miscible blends; however, the tensile modulus and strength of their blend fibers are comparable to, or better than, that of PBI fibers, depending on process conditions. Fibers spun from an 80/20 PBI/PS solution blend have PBI-like LOI (limiting oxygen indices) and flame shrinkage behavior. Sulfonation and stabilization of this fiber improve its thermal properties. The process window for these blend fibers has been determined. There was no aging phenomenon on as-spun PBI/PS blend fibers, while as-spun fibers made from PBI/polyarylate (PA) and PBI/high modulus aramides (HMA) exhibited remarkable aging effects on fiber properties. This difference probably arises from the fact that (1) the former is not a miscible blend, while the latter are; and (2) the former does not have hydrolysis groups, such as ester and amide groups, as that in the PA and HMA systems.
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    Polymer Engineering and Science 33 (1993), S. 1084-1084 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 91
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    Polymer Engineering and Science 33 (1993), S. 1110-1121 
    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 dielectric behavior of glassy thermoplastic polymer in the microwave frequency range was investigated. Specifically, the relationship between energy absorption and temperature for several thermoplastic systems was examined to test the theoretical basis for heating under microwave irradiation. Irradiation under traveling and standing wave conditions were explored. The heating rate versus temperature data at a frequency of 2.45 GHz yielded a microwave calorimetry procedure for examination of the dielectric and relaxation behaviors. Correlations were drawn between (a) the apparent activation energy and the critical temperature, and (b) the shape of the dielectric spectra at 2.45 GHz and its shape in the kHz region. WLF relationships were examined for glassy thermoplastics to show the difference in changing activation energy with temperature.
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  • 92
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    Polymer Engineering and Science 33 (1993), S. 1132-1140 
    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: Stoichiometric mixtures of DGEBA (diglycidyl ether of bisphenol A)/DDS (diaminodiphenyl sulfone) and DGEBA/mPDA (meta phenylene diamine) have been isothermally cured by electromagnetic radiation and conventional heating using thin film sample configurations. Fourier transform infrared spectroscopy (FTIR) was used to measure the extent of cure. Thermal mechanical analysis (TMA) was used to determine the glass transition temperatures directly from the cured thin film samples. Well-defined glass transitions were observed in the TMA thermograph for both thermal and microwave cured samples. Significant increases in the reaction rates have been observed in the microwave cured DGEBA/DDS samples. Only slight increases in the reaction rates have been observed in the microwave cured DGEBA/mPDA samples. Higher glass transition temperatures were obtained in microwave cured samples compared to those of thermally cured ones after gelation. The magnitude of increases of glass transition temperature is much larger for the DGEBA/DDS system than DGEBA/mPDA system. The microwave radiation effect was much more significant in DGEBA/DDS system than in DGEBA/mPDA system. DiBenedetto's model was used to fit the experimental Tg data of both thermal and microwave cured epoxy resins.
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    Polymer Engineering and Science 33 (1993), S. 959-970 
    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: It is of great importance to accurately measure or predict the Residence Time Distribution (RTD) in designing extruders and/or in setting up a proper operating condition, because chemical reactions depend significantly on the RTD and temperature when chemical reactions take place during the extrusion process. A previous method to predict the RTD can analytically determine RTD, Residence Time Distribution Function f(t) and Cumulative Residence Time Distribution Function F(t), based on a simplified two-dimensional velocity field in an extruder. However, this previous method cannot accurately take into account the three-dimensional circulatory flow inside the extruder. The present paper suggests a new method to accurately determine the RTD taking into account the three-dimensional circulatory flow and presents a new formula derived to calculate f(t). In order to demonstrate the applicability of the new method including the circulatory flow effect, RTD, f(t) and F(t) were calculated based on a three-dimensional velocity field obtained via a quasi-three-dimensional finite element analysis. It was found that the previous method has a tendency to underestimate the RTD, owing to the neglect of the three-dimensional circulatory flow in comparison with the new method.
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    Polymer Engineering and Science 33 (1993), S. 980-988 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Experimental data confirm the utility of the following simple equation in predicting the spin coating behavior of polyimide precursor solutions: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm h} = {\rm c\beta }_{\rm 0} {\rm k}^{{\rm \beta }_{\rm 1} } {\rm \omega }^{{\rm \beta }_{\rm 2} } {\rm t}^{{\rm \beta }_{\rm 3} } \quad\quad\quad\quad{\rm (1)} $$\end{document} in which \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {c = {\rm polymer\, solution\, solid\, weight\, fraction;}} \\ {\beta _i = {\rm fitted\, coefficient\, (Greek\, letter\, beta)};} \\ \quad{h = {\rm film\, thickness\, after\, cure\, or\, solvent\, removal};} \\ \quad{k = {\rm polymer\, solution\, kinematic\, viscosity, centistokes};} \\ {t = {\rm time},{\rm and;}} \\ \quad{\omega = {\rm wafer\, spin\, speed, rpm (Greek\, letter\, omega)}.} \\ \end{array} $$\end{document}.
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  • 95
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Ternary systems consisting of polypropylene (PP), ethylene-propylene-dieneterpolymer (EPDM) and different types of inorganic fillers (kaolin, BaSO4) have been investigated with respect to their mechanical behavior. On the basis of an Interphase model, it was possible using the modified van der Poel equation to describe the temperature dependence of the storage modulus G′(T) and the loss modulus G″(T). The interphase properties G′(T) and G″(T) could be calculated.
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    Polymer Engineering and Science 33 (1993), S. 1033-1041 
    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 nonlinear diffusion equation is used to study early-stage spinodal decomposition of polymer solutions, in relation to the membrane formation, in two dimensions. The effects of overall polymer composition and composition-dependent mobility and diffusivity are included in our simulations. Our results show a kinetically stable structure is established during the early stages, which corresponds to a circular range of peaks in the two-dimensional frequency spectrum. Such a spectrum is found to result in an interconnected cell structure in the two-dimensional real space. A decrease in the level of polymer interdomain interconnectedness is obtained as time increases, which indicates the influence of interfacial tension. As the overall polymer composition is increased, an increase in interdomain distances is observed, although the same early stage morphological structure is obtained. Finally, calculated interdomain distances from the two-dimensional simulation are larger than those obtained in equivalent one-dimensional model systems.
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    Polymer Engineering and Science 33 (1993), S. 1279-1287 
    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 finite element numerical analysis of preform inflation associated with the injection blow molding process has been developed using a neo-Hookean constitutive model. The analysis is capable of predicting final wall thickness distributions for axisymmetric mold geometries. Experimental studies were conducted on a Uniloy injection blow molding machine (Model 189-3 and Model 122). A twelve ounce (355 mL) cylindrical bottle mold was instrumented with contact sensors, thermocouples, and pressure transducers. Visualization studies of the inflation process were performed using specialized tooling and high-speed video cameras. The experimental studies provide justification for analyzing the deformation by means of a static elastic approach. The predicted wall thickness distribution is in reasonable agreement with the experimental data. Nonuniformities in the temperature distribution in the preform were found to have the most significant impact on the inflation behavior and the resulting wall thickness.
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    Polymer Engineering and Science 33 (1993), S. 1301-1307 
    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: Dielectric α-relaxation of a bisphenol-A type epoxide oligomer has been investigated in the vicinity of the glass transition temperature (Tg) by the direct current (DC) transient method. The logarithm of the DC transient current for the oligomer was well approximated by the third order function of the logarithm of time. The complex dielectric constant was calculated through the Fourier transformation of that approximation function according to Simpson's integration rule in a frequency range of 10-5 - 1 Hz. At the temperature around the Tg (45°C), the dielectric α-relaxation process of the oligomer was found to be governed by the Havriliak-Negami equation. The relationship between the DC conductivity (σ) and the dielectric relaxation time (τ), σ·τm = const, is valid near and above the Tg of the oligomer. The DC transient current method combined with the DC conduction and the dielectric bridge measurements is considered to be a practical tool for analyzing the dielectric α-relaxation process of the epoxide oligomer over a wide frequency and temperature range.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1065-1078 
    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 recirculating screw mixer (RSM), a new small-volume intensive mixer for the polymer laboratory, is designed, built, modeled, and tested. This type of batch mixer is intended for the mixing of 1 to 30 cm3 of viscous material at high shear rates. A material element in the mixer experiences alternating screw pump and tubular flows with reorientation between these flows. A mixer with a 10 cm3 sample capacity is built for testing and evaluation. Flow visualization experiments are used to investigate the quality of the distributive mixing achieved. The flows in the mixer are modeled for the cases of a Newtonian fluid and a power law fluid. The Newtonian model accurately predicts the recirculation time for particles suspended in Newtonian silicone oils. The power law model accurately predicts the screw torque obtained with a polystyrene and polyethylene. A method for the measurement of fluid rheology from the operating conditions of the RSM is proposed and tested. The mixing achieved by the RSM is compared to that obtained by a batch mixer with roller blades. Both mixers are used to prepare blends of ethylene-propylene rubber in polystyrene. The morphologies of the resultant blends are compared and differences in the mixing action are discussed. The mixers are also used to prepare composites of fumed silica in polyethylene. The quality of mixing obtained in the RSM compares quite favorably with that obtained in the batch mixer with roller blades for polystyrene/ethylene-propylene rubber reactive blends and polyethylene/silica composites.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1092-1109 
    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 objective of this effort has been to investigate the relationship between polymer structure and microwave absorptivity. Dielectric loss factor, ε″, loss tangent, tan δ, and oscillator strength, (εS -- ε∞), were used to evaluate potential material processability under applied microwave radiation. Numerous polymeric materials varying in chemical and physical structures were irradiated in a low power (≤ 100W) electric field at 2.45 GHz. Electromagnetic radiation was applied as either traveling or resonant wave modes in cylindrical and rectangular waveguides. In general, heatability was found to be a direct function of the dielectric loss dispersion dependence on temperature and frequency. The dielectric loss factor obtained at low frequency measurements was found to be directly proportional to the heatability of polymers. A WLF plot was used to predict the shift of dielectric loss maxima into or out of the microwave frequency range.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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