bluuebunny/crossref_metadata_2025 huggingface dataset:
The ABC's of extruder screw design
Authors: Rauwendaal Chris
Published: April 2003

Screw design for single screw extruders is a subject often surrounded by a certain degree of mysticism; in fact, by many people it is considered to be a black art. Others approach screw design from a mathematical point of view and determine the screw geometry from mathematical simulation of the extrusion process. Neither approach works very well. Our understanding of the extrusion process has improved considerably over the last 40 years. As a result, screw design certainly cannot and should not be considered a black art, because doing so would basically ignore all the progress made in the development of improved understanding of the extrusion process. On the other hand, relying only on mathematical modeling to achieve the desired extruder performance is not entirely appropriate, simply because the extrusion theory has not developed to the point that extruder performances can be predicted with 100 percent accuracy. The correct way to approach screw design is to combine extrusion theory and practical experience. As long as the extrusion theory is not fully developed, there is no substitute for practical experience. In this paper a practical approach to screw design is developed, with a minimal use of extrusion theory, to facilitate wider implementation of this approach. The design of the solids conveying, plasticating, melt conveying, and mixing zones of the extruder will be described based on a discussion on what physically happens to the material as it progresses along the extruder screw. It will be shown that the appropriate screw design is strongly dependent on the flow properties of the material to be extruded as well as the amount of pressure that has to be developed by the screw. This means that the screw design cannot be analyzed without consideration of the die that will be used at the end of the extruder. The design of the die, the melt flow properties of the polymer, the throughput rate, the melt temperatures, and the screen pack determine the amount of pressure that has to be developed by the screw. Therefore, the screw design that is appropriate in a regular extrusion operation is usually not optimum when a melt pump is used, because in the latter case the screw only has to develop a small amount of pressure.
Modeling plug‐assist thermoforming
Authors: Throne James L.
Published: April 2003

Plugs are sometimes used to prestretch thermoplastic sheet prior to drawdown into thermoform mold cavities. The amount of force required to stretch the sheet depends upon the material constants in the stress‐strain equation, the sheet thickness, the extent of stretching, and the geometry of the plug. Two decades ago, Williams proposed simplifying the general thin membrane large strain theory to obtain a tractable force‐deflection model. In this paper, it is shown that for plug forming, the general theory reduces to a relatively simple, transcendental relationship. Experimental force‐deflection data obtained on two thicknesses of natural rubber sheet agree reasonably well with the general theory but not at all with the Williams large strain model.
A finite element study of viscoelastic effects in double‐layer coextrusion of polymer melts
Authors: Luo X.‐L. , Mitsoulis E.
Published: April 2003

A finite element simulation of viscoelastic flows in double‐layer coextrusion of polymer melts has been performed. The constitutive equation used is a realistic integral model of the K‐BKZ type which can describe the viscoelastic memory characteristics of polymer melts. Viscosity and first normal stress data of typical PS and HDPE melts at 200°C are employed along with a feed ratio used in actual experiments found in the literature. Our results reveal important viscoelastic effects that could not be predicted by previous inelastic simulations. In particular, when the outer layer is more elastic than the inner layer, an enhanced extrudate swell is observed relative to the opposite configuration at the same flow rate, even if the outer layer is less viscous than the inner layer. In terms of a dimensionless stress ratio SR measured on the die wall, the more elastic material at the outer layer results in a higher SR value than that of the opposite configuration at the same flow rate. On the other hand, when the outer layer is less elastic than the inner layer, a reduced extrudate swell is observed relative to the opposite configuration at the same flow rate even if the outer layer is more viscous than the inner layer. When compared at the same SR value, however, our results show that the inelastic swell mechanism proposed by Tanner still applies qualitatively, i.e., a more viscous outer layer will result in larger extrudate swell than the opposite configuration.
Knit lines in reaction injection moldings
Authors: Maier Christian , Hrymak Andrew N. , Wood Philip E.
Published: April 2003

Knit lines in reaction injection molding (RIM) are formed when a fluid flow front passes through the mold cavity and must pass around objects in its path. Factors were ordered in importance of their effects on the deterioration in mechanical strength associated with knit lines. In order of decreasing importance, reactant temperature, mold temperature, and relative location (from the product) of the knit line sample were found to affect the knit line strength.
An experimental evaluation of flow distribution models for spiral mandrel dies
Authors: Perdikoulias John , Vlcek Jiri , Vlachopoulos John
Published: April 2003

Three recent mathematical models, developed to simulate the flow of polymer melts through spiral mandrel dies were analyzed. The models were compared against each other and with experimental data. The experimental data were obtained from processing several polymers through a 100 mm diameter spiral mandrel die attached to a 38 mm extruder. The die had no post‐spiral sections to ensure that only the effect of the spiral distribution system would be measured. The model developed by Vlcek et al. (Int. Polym. Process., 2, 174–181, 1988) was found to be the most accurate in predicting both the magnitude of the flow variation and the pressure drop.
Development of recycling technology for plastic fishing gear—a materials evaluation
Authors: Dagli S. S. , Kelleher P. G. , Monroy M. , Patel A. , Xanthos M.
Published: April 2003

The recycling potential of used plastic fishing gear by melt reprocessing is examined from a materials standpoint, as part of broader efforts to combat marine pollution caused by plastic debris. The present paper focuses on the identification of plastics and contaminants in a large variety of collected fibrous fishing gear, and the characterization of plastics in terms of possible degradation in the marine environment and their expected thermal stability during reprocessing. None of the major plastics involved (nylons and HDPE) was found to be significantly altered after exposure; accelerated thermal stability tests also indicate that these plastics could be reprocessed to acceptable products. Strong evidence suggests, however, that PP found in minor quantities would further degrade during extrusion. The presence of asphaltic and alkyd‐type coatings on the nylon fibers was shown to complicate the characterization and melt flow behavior. Preliminary data on extrusion conditions and the effects of coatings and additives on the mechanical properties of injection molded compounds are presented. General technical and economic aspects of complete recycling facilities are also discussed.
Measuring spatial fiber orientation—A method for quality control of fiber reinforced plastics
Authors: Fischer G. , Schwarz P. , Mueller U. , Fritz U.
Published: April 2003

Properties of short and especially long fiber reinforced thermoplastics highly depend on fiber length distribution in the processed material and local fiber orientation in the processed part. Good mechanical performance is achieved, if overall mean fiber length is high and fiber orientation is well adapted to the external stress situation. If non optimized processing parameters are applied, a decay in mean fiber length and unfavorably orientated fibers in areas of high stress may result. Knowledge of morphological parameters provides quantitative information about the injection molding process and the design of the cavity. Recent advances in automated methods of measuring fiber length and spatial fiber orientation, which are based on image processing systems, reveal even small differences in morphology. Measuring spatial fiber orientation on polished cross‐sections by means of an image processor is a newer concept, that allows fast and quantitative description and optimization of the mold filling process. Some examples show the performance of the method; the measured fiber orientation is used to model thermal expansion and Young's modulus.
Peroxide modified polyolefin blends: Part I. Effects on ldpe/pp blends with components of similar initial viscosities
Authors: Yu D. W. , Xanthos M. , Gogos C. G.
Published: April 2003

As part of a broader research effort to prepare polyolefin blends with controlled rheological and mechanical behavior, LDPE/PP blends were peroxide modified through reactive processing in intensive batch mixers. Polymers with similar initial viscosities and elasticities were first melt mixed and then simultaneously reacted and mixed to produce blends whose reaction‐modified components had very different molecular weights and molecular weight distributions. The rheological behavior of the blends in both shear and elongational flow were found to depend on composition, peroxide concentration, and, possibly, on the relative response rate of the individual components to peroxide attack. In general, the rheological properties of the reacted blends differed significantly from those of blends compounded in the absence of peroxide, and they were influenced by the presence of two components with vastly different structural and rheological characteristics: the degraded PP of low viscosity and elasticity, and a branched or crosslinked LDPE with increased viscosity and increased melt elasticity. Data from the batch experiments of this work are useful in defining process requirements for continuous reactive extrusion compounding, such as component characteristics, length of mixing/reaction zones, screw geometry, and sequence of feeding, as they relate to product characteristics.
Applications for thermotropic liquid crystal polymer blends,
Authors: Williams David J.
Published: April 2003

Thermotropic liquid crystal polymers (TLCPs) are being widely investigated for their potential as “blend additives” in the 5 to 30% composition range for thermoplastic resins. Motivation for this activity stems from the desire to impart some of the remarkable qualities of TLCPs to the host resin, including enhanced processing and self reinforcement. The barriers inhibiting this technology include high TLCP resin costs, absence of specialized processing equipment, and blend brittleness. These and other barriers are expected to decline as the technology evolves. In the meantime, TLCP blends are expected to find usage in high value added niche applications, where current barriers are not controlling and where their prices can be justified on the basis of performance. The market potential for several TLCP/thermoplastic polymer blends in film and fiber applications are explored. Film and fiber blends are believed to have high potential for near term technical and commercial success. The incentives for development appear to lie primarily with host resin suppliers and device fabricators, and not with TLCP suppliers. The former are expected to benefit from improved consumption and sales resulting from improved resin system and device performance.
Morphology and property control via phase separation or phase dissolution during cure in multiphase systems
Authors: Hsich Henry S.‐Y.
Published: April 2003

The morphology and properties of polymer alloys and blends can be controlled via phase separation or phase dissolution during cure. The morphology and properties control by phase separation was achieved by simultaneously manipulating miscibility, kinetics of phase separation, and cure reaction of polymer systems. Using phase diagrams consisting of binodal and spinodal curves, the morphology of epoxy/CTBN (carboxyl‐terminated butadiene acrylonitrile copolymer) systems can be controlled by the mechanism of nucleation and growth or by spinodal decomposition. We have found that the particle size of the rubber reinforcement in epoxies is affected by the mechanisms of phase separation. Phase separation by nucleation and growth gives larger rubber particles than the corresponding phase separation by spinodal decomposition. This contrast in the morphology development is the consequence of controlling phase separation through chemorheological behavior. Modification of the phase separation kinetics in epoxy/CTBN systems was extremely effective at altering both morphology and properties of these alloys. This technique offers a mean to shift the glass transition temperature of the rubber‐rich phase while leaving the glass transition temperature of the epoxy‐rich phase intact. Such control over morphology is the key to ultimately controlling material properties. The morphology and properties can also be controlled by phase dissolution during cure via invoking anion–cation interactions or intrachain repulsion forces. Phase dissolution in elastomer blending is the key for achieving optimal morphology having a synergistic effect in the polymer blends. The morphology and properties of NR (natural rubber)/EPDM blends were controlled through compatibilization and co‐vulcanization to promote phase dissolution during cure. A synergistic result in the blends was achieved by having an interconnected phase morphology. The domain sizes of the blends are 3–5 μm before cure and 1–2 μm after cure. These blends showed superior mechanical properties to those of the individual NR or EPDM, after a long term of high temperature aging.
Impact behavior of modified PVC for outdoor applications
Authors: Tseng A. A. , Borrosky M. A. , O'Connor S. M. , Knotts J. J.
Published: April 2003

A systematic study was conducted to determine the optimum polyvinylchloride (PVC) molecular weight and impact modifier concentration blend for the construction or outdoor application. This application called for a material with superior impact and weathering properties as well as cost efficiency. Three different molecular weights of PVC have been used in the present study. Impact modifier was blended with the PVC at various concentrations to improve its impact properties. The blends were extruded, pelletized, and injection molded for testing. Three types of impact tests, including the lzod, the Gardner, and the Dynatup impact tests, were conducted, all of which followed the ASTM Standards. A cost analysis was also conducted based on the relationship of the blend impact properties and their respective cost. The optimum blend developed has a molecular weight of 61,000 with an impact modifier concentration of six parts per hundred.
Report on the state of the art: Injection molding of fiber reinforced thermoplastics. Part I. materials and processes
Authors: Kelleher Paul G.
Published: April 2003

This is part of a survey of recent developments in injection molding of fiber reinforced thermoplastics. Topics discussed include materials and properties, the injection molding process with emphasis on fiber orientation and fiber lenght, advances in injection molding, as well as alternative methods for processing reinforced polymers.
PS–PMMA Block copolymer system as compatibilizer for PS–PVC blends
Authors: Caneba Gerard T. , Kandiraju Srinivasarao
Published: April 2003

We are studying the use of PS–PMMA block copolymer systems to improve the mechanical properties of immiscible PS–PVC blends. For a particular PS–PMMA block copolymer system, we found that effective compatibilization occurs at compatibilizer levels of 1–5 wt % in a 50/50 PS–PVC blend. In the samples, storage and stress relaxation moduli were at least midway between those of pure PS and PVC. On the other hand, the equivalent uncompatibilized blend exhibited storage and stress relaxation moduli that are much lower than those of the soft PVC component. Stress relaxation moduli of pure PS remained fairly constant with time, while a 25% drop was observed for pure PVC after 120 sec. Also after 120 s, stress relaxation moduli for the uncompatibilized blend exhibited a 20% drop, while a less than 10% drop was observed for the compatibilized PS–PVC blends.
Mathematical modeling of the pultrusion of epoxy based composites
Authors: Trivisano A. , Maffezzoli A. , Kenny J. M. , Nicolais L.
Published: April 2003

The thermokinetic and rheological behavior of epoxy based composites during the pultrusion of carbon fiber composites is analyzed using a mathematical model accounting for the heat transfer and the heat generation characteristics of polymerizable systems. An energy balance and a kinetic expression for the chemical reaction are simultaneously solved to calculate the temperature and degree of reaction profiles. Afterwards the viscosity as a function of the degree of reaction is computed applying a theoretical model. The dimensionless mathematical model is applied to the description and optimization of the process variables. General optimization criteria are identified and applied to compute, through a tailored numerical simulation, the optimum set of processing conditions for different case studies corresponding to different die temperatures, pulling speeds, and composite thicknesses.
Report on the state of the art: Injection molding of fiber reinforced thermoplastics. Part II. Design and manufacture
Authors: Kelleher Paul G.
Published: April 2003

This is the second part of a survey of recent developments in injection molding of fiber reinforced thermoplastics. Topics discussed include product design, mold design and fabrication, prototyping, product manufacture, and applications of these materials.
Output computation in the grooved‐barrel extruder with regard to various conveyance techniques
Authors: Potente H. , Stenzel H. , Bergedieck J.
Published: April 2003

Today the design of extruder screws for grooved barrel extruders is often still based on the known values of the designing engineers or on empirical methods. For some years theoretical approaches for the design of grooved‐barrel extruders have existed1–5 which are, however, not yet satisfactory in computing the output performance, especially in the pressure gradient dependent range. The article presented here introduces a technique for the computation of the output performance in grooved‐barrel extruders in the transport stiff as well as in the pressure gradient dependent range. This also allows the computation of optional multisection screws with shear and mixing sections. The equations are based on a physical–theoretical model that permits a precise statement about output performance and the relevant material‐, geometry‐, and process‐parameters.
Design and optimization of extrusion dies using computer based simulations
Authors: Rakos Ronald , Sebastian Donald
Published: April 2003

Computer based simulations can be used to design and optimize commonly used industrial dies thereby reducing the need for costly modifications of a poorly designed die. Strategies are presented for the design and optimization of three types of extrusion dies, a mandrel pipe die, a spiral blown film die, and a coat‐hanger sheet die. The development of the computer model for each of the dies is presented. The assumptions made in the model and the numerical techniques employed in each of the simulations are outlined. Numerous examples are given to illustrate how each of the design simulations is used.
Melting theory for temperature‐dependent fluids, exact analytical solution for power‐law fluids
Authors: Rauwendaal Chris
Published: April 2003

The first quantitative description of melting in single‐screw extruders was given by Tadmor around 1965. A simple analytical theory was developed for Newtonian fluids assuming the fluid viscosity to be unaffected by changes in temperature. Also, an approximate analytical theory was developed for a power‐law fluid assuming the power‐law constants to be independent of temperature and viscous dissipation to be negligible. Later workers extended the theory; however, most of these extensions did not allow closed‐form analytical solutions, thus requiring numerical techniques to obtain solutions. One of the most crucial assumptions in the analytical melting theory is the assumption that the viscosity of the polymer melt in the melt film is not affected by temperature differences in the melt film. This assumption has been eliminated in the improved melting theory by deriving and exact solution of the temperature and velocity profile in pure drag flow of a temperature‐dependent power‐law fluid between two parallel plates. It will be shown that the inclusion of the temperature dependence of the viscosity dramatically affects the predictions of the melting rate. It will further be shown how the new theory can be used to predict the optimum barrel temperature for melting.
Structure development in powder processing of polyphenylene sulfide
Authors: Jog Jyoti P. , Lodha Anjali , Nadakarni Vikas M.
Published: April 2003

The thermal and crystallization behavior of polyphenylene sulfide (PPS) in the context of its structure development in solid‐state processing is reported. The solid‐state processing of polymers involves cold compaction of the powder, followed by sintering. Since this process comprises of heat treatment at high temperatures for extended periods, the structure of PPS would be expected to be affected. An attempt has been made to elucidate the effect of compaction and sintering process parameters on the physical and chemical structures of the polymer. The changes in the structure of the polymer were monitored by characterizing its melting and crystallization behavior. It was observed that compaction resulted in changes only in the physical structure, leading to destruction of the smaller/less stable crystallities. The thermal treatment at high temperatures led not only to physical changes involving crystal growth and perfection but also to chemical changes in the structure, resulting in modification of crystallization behavior. The extent of change was found to be different for PPS in the powder form and in the pellet form, which is explained on the basis of the restricted diffusion of air in pellet form as compared to the powder. Such changes observed in the samples were also dependent on the type of sintering medium. The sintering in presence of nitrogen did not show significant changes in the crystallization or melting behavior. Thus, the structure development in solid‐state processing of PPS was influenced by the sintering time, temperature, and sintering medium, leading to physical and/or chemical changes.
Postmolding and load‐induced deformation analysis of plastic parts in the injection molding process
Authors: Santhanam N. , Chiang H. H. , Himasekhar K. , Tuschak Peter , Wang K. K.
Published: April 2003

To assess warpage and shrinkage of an injection‐molded plastic part, an integrated computer‐aided engineering (CAE) system has been developed. This integrated system employs a simultaneous analysis of the compressible fluid flow, heat transfer, and residual stresses in the polymer during the filling and postfilling stages of the injection molding process and of mold cooling/heating that occurs throughout the entire process. Using the polymer temperature and pressure distributions as a function of time, an analysis has been performed to predict the residual stresses, treating the polymer as a viscoelastic material. The resultant loading is interfaced with the structural analysis program ABAQUSTM to predict the postmolding shape of the plastic part. Analysis has also been performed to evaluate the load‐deflection behavior of a molded part and the effects of different degrees of material anisotropy.
Report on the state of the art: Reactive processing using twin‐screw extruders
Authors: Sakai Tadamoto
Published: April 2003

Reactive processing technology is rapidly coming into widespread use in the plastic industry as a tool for both simplifying conventional polymerization processes and creating innovative polymers and their alloys. For a long time, we have been making great efforts to develop the technology and systems related to this field. In this report, we describe fundamental functions of twin‐screw extruders and introduce some applications of reactive processing using the twin‐screw extruder. Furthermore, we discuss the future trends of this technology.
Initiation of a solid‐state extrusion of a cross‐linked silicone rubber
Authors: Cohen A. , Burmester A. F.
Published: April 2003

Initiation stage of a plunger‐driven extrusion of a cross‐linked silicone rubber material was investigated. The experiments were performed at room temperature with a series of capillaries of various diameters positioned in a conventional Instron rheometer. It was observed that the extrusion of the rubber started with a cylindrically shaped “plug” which was followed by an “apple peel” shape. This change in the shape of extrudates corresponds to changes in the load applied to the plunger. Analysis of this transition and its variation with the size of the capillary points to interesting physical mechanisms involved in this solid‐phase processing operation.
Metal injection molding: Freedom in design for sintered metal components
Authors: Bielzer Raffael , Michaeli Walter
Published: April 2003

Metal injection molding represents a combination of sintering and injection molding technology. The shaping is performed by injection molding and the compaction into the definitive part by sintering. Shaping starts with the metal powders and binders being mixed, homogenized, and worked up to a granulate. The granulate is now processed to the so‐called green compact on an injection molding machine. Injection mold processing of powder metal is basically comparable to pure thermoplastics. After forming, the green compact must be compacted to the final, purely metallic component. To this end, the binder part must be removed from the body, which is subsequently sintered down to its final density. This article touches upon aspects of the problems and questions arising from powder–metal injection molding. The objective is to provide an insight into a promising production process.
Computer prediction of cycle times during rotational molding of plastics
Authors: Nugent P. J. , Crawford R. J. , Xu Liang
Published: April 2003

A computer simulation program has been developed for the rotational molding of plastics. The predictions obtained from this program in terms of heating/cooling rates and overall cycle times have been compared with experimental molding trials with a range of plastics. It is shown that the computer model predicts accurately the real situation for a wide range of processing conditions. In particular, the program allows the effects of oven efficiency, mold material, mold wall thickness, and molded part thickness to be assessed quantitiatively. The article presents information on heat transfer coefficients that are applicable during rotational molding and typical cycle times for a wide range of process conditions. © 1992 John Wiley & Sons, Inc.
Thermoplastic polymer formulations: An approach through experimental design
Authors: Sell Joseph W. , Lepeniotis Stefanos S.
Published: April 2003

An approach to modify a thermoplastic polymer's cost–property profile is through polymer blends and glass reinforcement. An experimental design for a thermoplastic polymer formulation was done using RS/Discover® and EChip®. Here, two crystalline thermoplastic polymers have been compounded with fiber glass to reduce cost and maintain useful melt processing properties and physical properties. Using RS/Explore and EChip software, the results were analyzed by regression analysis and the results summarized in contour plots. The ease of use and resultant format of the data analysis from these software packages are compared. A total of 10 responses were measured and analyzed in this experiment and multivariate data analysis was incorporated where appropriate. © 1992 John Wiley & Sons, Inc.
Thermoplastic epoxies from n‐alkylamines
Authors: Huang Jan‐Chan , Gu Fan
Published: April 2003

Thermoplastic epoxy resins have some special applications. In this study, the diglycidyl ether of bisphenol‐A and three different monoamines—butylamine, hexamine, and dodecylamine—at different epoxy–amine ratios were used to make epoxy resins. Relative viscosity, hardness, Vicat softing temperature, volume resistivity, and refractive index were investigated. As amine contents approach the equivalent value, these properties reach the maximum value except the refractive index, which decreases continously with increasing amine content. When the carbon number of amines increases, the properties decrease except volume resistivity. Refractive index values vary with composition, suggesting a possibility of producing epoxies with a desired refractive index for optical applications. © 1992 John Wiley & Sons, Inc.
Fundamentals of polymer compounding: The phase‐inversion mechanism during mixing of polymer blends
Authors: Shih Chi‐Kai
Published: April 2003

During a routine extrusion compounding of a polymer blend of polyarylate resin and ethylene/acrylate rubber, an unexpected powdery product instead of a cohesive mixture was obtained. Also, the 20% rubber component was not well dispersed in the final product. This process problem was studied by simulation with a laboratory internal mixer following the procedure discussed by Shih. The powder formation was successfully reproduced. From the results of continuous video monitoring and analyses of the intermediate samples collected during the simulation experiments, we found that the progression of mixing from solid pellets to a cohesive mixture in a batch mixer or a twin‐screw extruder needs to “climb over” a prolonged transition state where the plastic polyarylate was dispersed in the 20% rubber. The finding led to two successful solutions to the powdering problem. A “phase‐inversion” mechanism is proposed to explain the observed morphological changes. This mechanism appears to have wider applicability in the processing of polymer blends. © 1992 John Wiley & Sons, Inc.
Compatibilization and toughening of PPE—PP blends with hydrogenated, styrene—diene block copolymers
Authors: Akkapeddi M. K. , Vanbuskirk B.
Published: April 2003

Simple blends of poly(2,6 dimethyl 1,4‐phenylene ether) (PPE) and polypropylene (PP) are highly incompatible and consequently quite brittle regardless of the molecular weights and ductility of the individual components. Hydrogenated, styrene‐diene block copolymers, viz. S‐EB‐S triblock and S–EP diblock copolymers, can be used to compatibilize and toughen the blends. The ductility and impact toughness of the PPE–PP blends depend not only upon the nature of styrene block copolymers but also on the nature of PPE and PP used. It was found that lower‐molecular‐weight PPE was actually better in achieving a blend with desired combination of high‐impact toughness and high heat distortion temperature. Compatibilization efficiency and morphological considerations influencing the blend's properties are discussed. © 1992 John Wiley & Sons, Inc.
Modeling of membrane inflation in blow molding: Neural network prediction of initial dimensions from final part specifications
Authors: Diraddo R. W. , Garcia‐Rejon A.
Published: April 2003

The use of neural networks in the modeling of the inflation stage of the blow molding process is discussed. The simulation is enacted in the reverse process direction, predicting initial membrane dimension requirements from final part thickness distributions. This situation has practical implications because tooling costs and machine down times can be minimized with the information obtained. The optimal network topology entails simultaneous pre‐ and postprocessing of the data. An adaptive window is employed for modeling of the effects of adjacent segments. The optimal window length is 16 for both the input and output layers in the network topology. Simulations are run for bottles blown using various constant and pulsed die gaps. © 1993 John Wiley & Sons, Inc.
Blends of polypropylene and nylon 6: Influence of the compatibilizer, molecular weight, and processing conditions
Authors: La Mantia F. P.
Published: April 2003

The aim of this work is to study the influence of different types of compatibilizing agents, different processing conditions, and the molecular weight of the two components on the properties of immiscible blends of polypropylene and nylon 6. Increasing the content of the functional group of the modified polypropylene and the content of nylon in the blend, the effectiveness of the compatibilization improves. The same effect is observed by decreasing the molecular weight of the two components, in particular, that of the polyamide. The influence of the processing conditions is slight provided no degradation takes place during processing. © 1993 John Wiley & Sons, Inc.
Analysis of PVC blends by three‐dimensional solubility parameters
Authors: Huang Jan‐chan , Chang David C. , Deanin Rudolph D.
Published: April 2003

An investigation was undertaken on the application of the three‐dimensional solubility parameter method to predict miscibility of polyblends. The three‐dimensional method attempts to account for the combined effects of dispersion, polar, and hydrogen bonding interactions between molecules. This study focused mainly on the miscibility of blends of poly(vinyl chloride) (PVC) with homopolymers as well as with copolymers. The three components of solubility parameters were calculated from the group contributions of the structural units of the polymers. By comparing the parameters of different PVC blends in two categories, PVC/homopolymer and PVC/copolymer blends, the miscibility trend of PVC blends was revealed. The three‐dimensional solubility parameter approach successfully predicted the miscibility of several homopolymers. For copolymers, the chance of miscibility was increased because of the ability to adjust the solubility parameter through composition. This was reflected in a smaller distance between the solubility parameter of copolymer and that of PVC. Experimental results reported in the literature confirmed this conclusion. © 1993 John Wiley & Sons, Inc.
Mechanochemical bonding of hard‐to‐bond materials
Authors: Vakula V. L. , Genel L. S. , Kestelman V. N.
Published: April 2003

Some new aspects of mechanochemical treatment are reported. The method is developed to bond such specific materials as polytetrafluoroethylene, polyethylene, polypropylene, and others that are known as hard‐to‐bond materials. The new method possesses such advantages as low cost, simplicity, high strength of adhesive joints and stability of properties. © 1993 John Wiley & Sons, Inc.
Effect of solid–state modified polypropylene on the physical performance of sawdust–filled polypropylene composites
Authors: Sain M. M. , Kokta B. V.
Published: April 2003

The influence of solid‐state modified polypropylene on the physical performance of uncoated or thermoset‐resin coated sawdust‐filled polypropylene composites was studied. The effect of composition of the composites on tensile strength, Young's modulus, tensile toughness, elongation, and impact strength was determined through two 23 factorial rotatable designs. The results of this investigation show that both the m‐phenylene dismaleimide‐modified polypropylene precompounded sawdust as well as solid‐state modified maleated polypropylene can be successfully used to prepare sawdust‐filled polypropylene composites with good tensile strength. On the whole, this property improved compared to that of unfilled polypropylene. According to the analysis of factorial design, the optimum composition to prepare a composite with highest tensile strength within the experimental range was 30–40 wt% phenolic resin coated sawdust together with 4–6wt% solid‐state modified maleated polypropylene; while the product composition for the worst design was a combination of high amount of phenolic resin modified polypropylene with phenolic resin coated sawdust. The experimental design also concluded that effect of compositions on impact strength of composites was not significant in most of the cases. Overall, the empirical models constructed in this study provided a good approximation to actual experimental measurements; we are encouraged to extend this approach to processing conditions for manufacturing these composites. © 1993 John Wiley & Sons, Inc.
The microwave processing of polymeric materials
Authors: De Meuse M. T. , Ryan C. L.
Published: April 2003

An overview is presented of the currently studied microwave‐assisted chemical and physical processes, as they pertain to polymers. Furthermore, the features which affect the microwave heating of polymers are described. Finally, some of the factors which have limited more widespread acceptance of microwave processing of polymeric materials are highlighted. © 1993 by John Wiley & Sons, Inc.
Sheet coextrusion of polymer solutions and melts: Comparison between simulation and experiments
Authors: Hannachi A. , Mitsoulis E.
Published: April 2003

Coextrusion flows of polymer solutions and melts to produce polymeric sheets are studied employing (a) the Lubrication Approximation Theory for a quick determination of interface development and pressure drops for each material; and (b) the Finite Element Method, which uses a u‐v‐p‐T‐h formulation for the velocities, pressures, temperatures, and interface location and solves in the flow domain the full conservation and constitutive equations. The determination of the interface is part of the solution process. Simulations have been carried out for several cases of two‐layer coextrusion of polymer solutions (Oppanols, i.e., polyisobutylenes) and compared with experimental data available in the literature. A three‐layer coextrusion case is also studied with a barrier ethylene vinyl alcohol and an adhesive layer tying a polystyrene layer, and the results are compared with experimental data. For low flow rates, the interface location agrees closely with experiments. For high flow rates, a tendency for encapsulation occurs, which cannot be captured by the present purely viscous two‐dimensional simulations. © 1993 John Wiley & Sons, Inc.
An integrated approach for modeling the injection, compression, and resin transfer molding processes for polymers
Authors: Liang Erwin W. , Wang H. P. , Perry Erin M.
Published: April 2003

An integrated finite element process simulator has been developed for modeling the injection, compression, and resin transfer molding processes for polymeric materials. The similarities among the three processes permit consolidation of the models into an integrated software package with low maintenance and ease of future extension. An introduction to the integration algorithm embedded in the process simulator is followed by models for injection, compression, and resin transfer molding. The validation of the injection molding portion of the integrated simulator is then addressed by comparing pressure history and filling patterns between the simulator predictions and experimental data. Tooling, processing, and quality issues—such as gating and venting design, weldline locations, and pressure and closing force requirements—are illustrated by two examples, a 3‐D fan blade and a ribbed box. © 1993 John Wiley & Sons, Inc.
Cross‐Linking of polypropylene by peroxide and multifunctional monomer during reactive extrusion
Authors: Kim B. K. , Kim K. J.
Published: April 2003

Polypropylene (PP) powder was extruded in the presence of peroxide and multifunctional monomers at varying concentrations. With increasing peroxide concentration, MFI increased almost linearly, whereas hardness, modulus, and impact strength decreased, and the results were interpreted in terms of decreased molecular weight and its distribution by chain scission. On the other hand, triacrylate type multifunctional monomers (PETA and TMPTA) reduced the MFI of PP upon extrusion, and led to increase of Tm and Tc followed by increased modulus, yield strength, and elongation as well. TAIC and PBQ exerted effects smaller than triacrylate type. When the multifunctional monomers were added to the 0.01 phr peroxide containing system, MFI decreased below that of peroxide, and increased above that of multifunctional monomer of the same concentration, and synergistic physical properties were generally obtained, especially at low content of coagent. However, at higher peroxide concentration (0.05 and 0.1 phr) MFI increased with PETA and TMPTA, and decreased with PBQ. In general, increase and decrease of MFI were respectively followed by the decrease and increase of modules, strength, and impact strength as well. © 1993 John Wiley & Sons, Inc.
Solid state processing of polymers: A review
Authors: Jog J. P.
Published: April 2003

The solid state processing technique is used for processing of a variety of polymers such as ultra high molecular weight polyethylene, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyether etherketone, and polyphenylene sulfide. The solid state processing involves cold compaction of polymeric powders followed by sintering at temperatures above their melting point. The properties of such products are influenced by the powder characteristics and a number of process parameters encountered during the compaction and sintering processes such as compaction pressure, rate of compaction, sintering temperature, and time. The understanding of the physical processes involved in solid state processing of polymers is essential for defining the parameters to obtain the product with desired properties. In this review, the various aspects of solid state processing are discussed with reference to the physical processes. © 1993 John Wiley & Sons, Inc.
Advances in injection molding of fiber‐reinforced thermoplastics during 1991—Part II: Processing, design, and manufacture
Authors: Kelleher Paul G.
Published: April 2003

This article is the second part of a survey of developments in the open literature during 1991 on subjects related to the injection molding of fiber‐reinforced thermoplastics. Topics discussed include injection molding machines, screw design, process control systems, modeling, product design, mold design and manufacture, characterization techniques, and applications of composites. Although these technological advances are broadly applicable to the processing, design, and manufacture of thermoplastics generally, they are essential to the enhanced engineering, fabrication, and utilization of fiber‐reinforced thermoplastics. © 1993 John Wiley & Sons, Inc.
Pressure‐related driving forces in the fully filled nonintermeshing twin screw extruder
Authors: Bigio David I. , Ramanthan Mohan R. , Herman Paul
Published: April 2003

Research in understanding the mechanisms behind driving forces in the fully filled nonintermeshing twin screw extruder concentrated on experimental analysis of the relation between stagger, screw speed, and cross‐channel flow due to measured pressure differential in the nip region. A new measure of the pressure driving force was also sought out, to correlate new data to previous findings from visual studies. The first part of the study was to obtain the values for the dynamic pressure on both sides of the nip region. Further refinements to the equipment used in previous studies allowed closer placement of the transducers in the nip region. After the data were stored, analysis started by determining the δp values from the trace of the pressure differential. By plotting these values, we obtain a highly repeatable curve confirming that the greatest pressure flow occurs at small staggers. A simple 2‐D model for pressure flow in the nip region was used to estimate the effect of the cross‐channel pressure differential. Values for the cross‐channel pressure flow were calculated and compared with the drag flow and found to be significant. © 1993 by John Wiley & Sons, Inc.
Intelligent processing of polymer sheets for calendering
Authors: Tseng A. A. , Shih W. H. , Thomas C. L. , Chen S. J.
Published: April 2003

The Intelligent Processing of Materials (IMP) concept has been applied to the calendering process with the goal of improving shape quality and process efficiency. All four basic features of the IPM, including modeling, data processing, sensing, and controlling, are considered. In the process modeling, bending and thermal models are developed. With these models, the relationship between the process parameters and quality of the calendered sheets has been established. A material data bank has been established to couple with the process modeling and real‐time sensing data. In sensing, ultrasonic and temperature sensors have been implemented to measure critical quality and process parameters in situ. The sensing data have been used not only to verify the modeling prediction but also to establish information needed to diagnose the causes of the layflat problem. Based on the model prediction as well as sensing information, a better control system to alleviate layflatness problems has been developed. Finally, a control strategy for future improvement of the calendering system is proposed. © 1993 by John Wiley & Sons, Inc.
The precise determination of polydispersity index (PI) in rheological testing of polypropylene
Authors: Shang S. W.
Published: April 2003

The polydispersity index (PI) of polypropylene (PP) obtained from plotting the crossover point of shear storage modulus (G′) and loss modulus (G″) was comparable to that using gel permeation chromatography (GPC). The precise PI determination was dependent upon the material properties of PP and rheological measurement technique. The effect of testing percent strain on PI was determined over a wide range of melt flow rate (MFR). The employed percent strain could affect PI of this percent strain was not independent of the frequency at the crossover frequency of the resin. To measure PI precisely, a 5% strain was recommended for MFR ≥ 30, while a 15% strain was suitable for MFR < 30. © 1993 by John Wiley & Sons, Inc.
Structure and properties of nucleated random and block copolymers of propylene
Authors: Sterzynski Tomasz , Lambla Morand , Crozier Hervé , Thomas Michel
Published: April 2003

The addition of various nucleating agents to a polymer leads to the modification of its crystalline structure, i.e., the formation of small spherulites with consequent changes in mechanical and optical properties. The aim of our research was to determine the role of nucleating agents on the crystallization of propylene copolymers. Random and block copolymers containing propylene and low amounts of ethylene were used in formulations with nucleating agents based on derivatives of sorbitol such as dibenzylidene sorbitol (DBS) and para‐methyldibenzylidene sorbitol (MDBS). The introduction of low concentrations of DBS and MDBS leads to significant changes in the crystalline structure with respect to α and β phases, as well as in the kinetics of crystallization. Using WAXS, DSC, optical microscopy, and tensile testing, the following changes of nucleated propylene copolymers were observed: (a) an increase in the crystallization temperature; (b) an increase of the level of crystallinity; (c) a considerable decrease of the size of spherulites (i.e., an improvement of the transparency of the random copolymers); (d) a decrease of the amount of the β phase in block copolymers; (e) an increase in tensile strength at yield; and (f) an increase in secant modulus. In most cases we found that the most efficient nucleating agent was the MDBS. © 1994 John Wiley & Sons, Inc.