bluuebunny/crossref_metadata_2025 huggingface dataset:
An improved lattice‐fluid equation of state for pure component polymeric fluids
Authors: Panayiotou C. , Vera J. H.
Published: December 2004

The Fluid‐Lattice Theory (Ising Fluid), recently tested by Lacombe and Sanchez, has been modified by introducing the typical Flory's surface‐to‐volume ratio of the characteristic‐segment of a polymeric liquid. This surface‐to‐volume ratio is not an adjustable parameter. It is obtained from Bondi's tabulations. The resulting new equation of state has three adjustable parameters per component and it represents a definite improvement for the fitting of P‐V‐T data for polymeric liquids. Extension to mixtures is not tested in this work but, in principle, it can be done by well‐established methods.
Effect of the addition of ethylene‐propylene random copolymers on the properties of high‐density polyethylene/isotactic polypropylene blends: Part 1—morphology and impact behavior of molded samples
Authors: D'Orazio L. , Greco R. , Mancarella C. , Martuscelli E. , Ragosta G. , Silvesrte C.
Published: December 2004

Two random commercial ethylene‐propylene copolymers (EPM) with different ethylene content have been added to binary isotactic polypropylene (iPP)/high density polyethylene (HDPE) blends by melt mixing in a Brabender‐like apparatus. Impact Izod tests and a morphological analysis on the fractured surfaces of broken specimens have been performed and discussed, in order to improve the deficiency in toughness of the binary HDPE/iPP mixtures. The results show that the impact performance of both homopolymers and HDPE/iPP binary blends is strongly improved by the addition of the EPM copolymers. Such an effect is related to the fact that the overall morphology, as well as the mechanism and mode of fracture, are greatly modified by the presence of such additives. The extent is dependent on factors such as the nature of the matrix (HDPE or iPP), the composition, and the chemical structure and/or the molecular mass of the added copolymer.
A plasticating model for single‐screw extruders
Authors: Fukase Hisahiko , Kunio Takeshi , Shinya Sadahiko , Nomura Akihiro
Published: December 2004

By measuring the solid‐bed transfer velocity, width and thickness under various conditions, die following results are obtained. As the result of melting, the solid bed decreases in width and thickness almost with the same rate, and the solid‐bed transfer velocity is constant, while a melt layer exists between the solid bed and the screw root; also, when the phenomenon of dam‐up occurs, caused by the combined effect of decreasing depth of the screw channel with tin insufficient decrease of solid‐bed thickness, the transfer velocity increases proportional to the rate of decrease of channel depth. Consequently, the solid bed is considered to behave us loosely packed particles. A new plasticating model is developed by making the above results an assumption and adopting finite differential calculus with the Newton‐Raphson method to obtain accurately the melting velocity, melt profile, and solid‐bed temperature. Calculated values are in remarkably good agreement with the experimental values Solid‐bed softening point, pressure, and screw torque are also successfully estimated.
Mechanical criteria for polymer compatibility: Poly(vinylchloride)/post‐chlorinated poly(vinylchloride) blends
Authors: Clark Debra D. , Collins Edward A. , Kleiner Lothar W.
Published: December 2004

The compatibility of poly(vinylchloride PVC) with post‐chlorinated PVC (CPVC) is investigated with the purpose of relating the mechanical properties of such blends with their compatibility. The effects on compatibility of varying mixing methods, blend composition, molecular weights of components, and chlorine content of CPVC are studied. Experimental methods include comparison of the glass transition temperatures (Tgs) of blends and homopolymers using dynamic mechanical analysis, Differential Scanning Calorimetry (DSC), and comparison of the mechanical properties of blends and homopolymers. Experimental results indicate marginal compatibility between PVC and CPVC. Blends in which CPVC is the main component are indicated to be less compatible than other compositions.
Fracture toughness and fatigue of polystyrene, polyphenylene oxide and their blends
Authors: Serrano A. M. , Welsch G. E. , Gibala R.
Published: December 2004

Blends of atactic polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) represent a compatible system that exhibits a transition from a crazing to a shear bending mode of deformation as a function of composition. PS (Mw = 30,000; Mw/Mn = 1.06) exhibited a value of \documentclass{article}\pagestyle{empty}\begin{document}$ K_{IC} = 1.00 \pm 0.20{\rm }MPa\sqrt m $\end{document}. Blends of up to 60 wt.% PPO exhibited \documentclass{article}\pagestyle{empty}\begin{document}$ K_{IC} \sim 1.00{\rm }MPa\sqrt m $\end{document}. However, there is a very rapid increase in KIC with increasing PPO content in the vicinity of 75 percent PPO. Fatigue behavior of the blends parallels that under static loading.
Dynamic mechanical behavior of filled polyethylenes and model composites
Authors: Chacko V. P. , Karasz F. E. , Farris R. J.
Published: December 2004

The effect of CaCO3 filler presence and CaCO3‐polymer interface character on the dynamic mechanical spectra of three polyethylenes with different molecular weights was investigated. Differences in storage modulus and loss tangent were observed for different polymer‐filler coupling and polyethylene molecular weight. The dynamic behavior of model composites was estimated using the, etastic‐viscoelastic correspondence principle, and these predictions were compared to the behavior of real materials.
Effect of short glass fibers and particulate fillers on fatigue crack propagation in polyamides
Authors: Lang R. W. , Manson J. A. , Hertzberg R. W.
Published: December 2004

The fatigue crack propagation (FCP) behavior (at 10 Hz) of several commercial short‐glass‐fiber and mineral‐reinforced nylon composites has been investigated. The FCP rates can be described in terms of the well‐known Paris relationship. Significant improvement in FCP performance was found for the glass‐fiber‐reinforced materials in comparison to that of the pure matrix materials (nylon 66 and nylon 612). Also, the FCP resistance was found to increase with increasing fiber content and interfacial adhesion for nylon 66. Despite the fact that specimens were cut from injection‐molded plaques, no or only slight effects of orientation were observed by testing specimens with cracks growing parallel and perpendicularly, respectively, to the major flow direction. Electron microscopy studies of fracture surfaces revealed a complex pattern of fiber orientation, varying over the plaque thickness and consisting of layers with fibers oriented mainly parallel, perpendicularly, or randomly to the major flow direction; nevertheless, the specimens behaved quasi‐isotropically. Significant differences in fracture mechanism were observed, depending on the matrix, the interfacial bonding, and the crack speed. In contrast to the fiber‐rein forced nylons, the mineral‐reinforced material exhibited poorer FCP resistance than neat nylon 66, even though the former is superior in tensile and impact behavior.
Studies of epoxy resin systems: Part C: Effect of sub‐Tg aging on the physical properties of a fully cured epoxy resin
Authors: Chang T.‐D. , Brittain J. O.
Published: December 2004

The effect of sub‐Tg aging on the properties of an epoxy resin system, diglycidyl ether of butanediol, DGEB, cured with 4‐4′ diaminodiphenyl sulfone, DDS, has been studied. Aging was found to increase the DSC (differential scanning calorimetric) endothermic peak, the density, and the upper yield point. In contrast, the lower yield point was relatively unchanged. This result, together with the observation of the elimination of the DSC endothermic peak by deformation and the absence of a yield point after deformation, suggested that the aging effect was eliminated by deformation. The thrermally stimulated depolarization (TSD) α‐peak was found to decrease in strength with aging time. All of the observations were best rationalized on the basis of the free‐volume concept.
Filling thin cavities of variable gap thickness: A numerical and experimental investigation
Authors: Hieber C. A. , Socha L. S. , Shen S. F. , Wang K. K. , Isayev A. I.
Published: December 2004

A theoretical and experimental investigation is presented for filling thin cavities of variable gap thickness. The modeling is based upon a finite‐element/finite‐difference formulation for an inelastic power‐law fluid and includes the effects of viscous heating and conduction upon the flow dynamics. Extensive results are presented for polypropylene and polystyrene melts injected into two variable‐gap‐thickness cavities, of which one has an insert. Good agreement is found between the predictions and measurements concerning the shape of the advancing melt front, the location of weld lines, and the temporal pressure trace at various positions in the cavity.
A study of structural development in the high speed spinning of poly(ethylene terephthalate)
Authors: George H. H. , Holt A. , Buckley A.
Published: December 2004

In recent years the spinning speeds of poly(ethylene terephthalate) (PET) fiber have increased to the point that significant structural development is being observed in the spun yarn. At even higher speeds significant crystallization has been obtained. Data characterizing these yarns will be presented and discussed showing the development of crystals and that the onset of this phenomena is related to the stress at the “freeze point.” The “freeze point” rises from around Tg at low speeds to the order of 200°C at high speeds. The spinline itself has been characterized by velocity and orientation profiles which show the crystallization process is extremely rapid, occurring over a few centimenters of the spinline.
Predicting conversion using temperature as the measured variable in the RIM process. Part I: Simulation and measurement structure
Authors: Romagnoli J. , Castro J.
Published: December 2004

In general the monitoring and control of many industrial processes is so complicated by problems associated with the on‐line measurement of the desired objectives that they must be inferred from available measurements. This leads to a state estimation problem in which the selection and adaptation of the structure of the measurements plays an important role. In particular, in the reaction injection molding (RIM) process, an accurate on‐line estimate of the conversion field is highly desirable. Since conversions cannot be determined readily by direct measurements, and a thermocouple can provide reliable dynamic temperature data, we can predict the conversion field from the solution of a state estimation problem using temperature as the measured variable. In this article, we describe an algorithm for designing the optimal arrangement of measuring sensors and analyze the RIM process dynamics which influence the structure depending on the operating conditions. The search for the optimal measurement structure for the purpose of state estimation makes up the bulk of the results. No particular estimation‐control strategy is investigated in this paper. Work is underway to develop the on‐line corrective system, which will use the temperature measurements to correct model predictions. The results of that work will appear in part II of this series.
Analysis of the puncture of a bisphenol‐a polycarbonate disc
Authors: Nimmer R. P.
Published: December 2004

The finite element technique is applied to analytically predict the response of a disc made of BPA‐polycarbonate during a displacement‐controlled puncture test with a hemispherical indenter. The analysis includes effects of contact load, large displacements and rotations, and large strains and material yielding. Two general topics are addressed with this analysis. First, it is shown that the load‐displacement behavior of impacted, BPA‐polycarbonate plates can be accurately predicted over a wide range of engineering interest (strains up to 30 percent) using a bilinear representation of the stress‐strain curve and flow theory of plasticity. For this purpose, the von Mises criterion is applied to define yielding in a generalized biaxial stress state, and strain rate effects are incorporated through the use of a yield stress consistent with the initial strain rate during the test. Second, in order to broaden the understanding of results associated with this widely used test, a number of mechanical and material effects are discussed, including large displacements, friction at the clamped support and indenter head, and clamping pressure at the support. Lack of agreement between the present analysis and experimental results with regard to ultimate load at puncture suggests that strain hardening and strain rate hardening of the material during the high‐strain portion of the test (30 percent‐60 percent) must be more accurately modeled for improved predictive capability.
Thermokinetic modeling of an epoxy resin I. Chemoviscosity
Authors: Tajima Y. A. , Crozier D.
Published: December 2004

It is shown that the Williams‐Landel‐Ferry equation can be taken to describe the temperature dependence of viscosity of an amine‐cured epoxy resin. Furthermore, for this resin system, the two parameters of the W‐L‐F equation can be expressed simply as functions of hardener concentration. Since the hardener concentration decreases with advancement, and since the reaction rate equation for advancement is readily determined and known, the viscosity can be calculated over any temperature (cure) cycle.
Thermal aging study of carboxyl‐terminated polybutadiene and poly(butadiene‐acrylonitrile)‐reactive liquid polymers
Authors: Okamoto Y.
Published: December 2004

A thermal aging study of carboxyl‐terminated polybutadiene (CTB) and poly(butadiene‐acrylonitrile) (CTBN) reactive liquid polymers has been conducted at 50°, 75°, 100°, and 125°C. All CTB and CTBNs are stable at 50°C aging. On aging at higher temperatures prior to use, viscosities of CTB and CTBNs increase, and terminal carboxylic acid functional groups start disappearing. Rate of viscosity increase and rate of carboxylic acid functional group disappearance increase with higher aging temperature and also with higher cyano group concentration in the polymers. The major cause of rapid viscosity increase and disappearance of carboxylic acid functional groups seems to be crosslinking between terminal carboxylic acid groups and cyano groups, which form imide structures. Crosslinking among the unsaturation in polybutadiene segments may contribute to the slow, steady viscosity increase. No acid‐anhydride formation and decarboxylation reaction, which may also result in viscosity increase and disappearance of carboxylic acid functional groups, are observed during the thermal aging at elevated temperatures.
Orientation development in thermotropic liquid crystal polymers
Authors: Ide Yoshiaki , Ophir Zohar
Published: December 2004

Thermotropic liquid crystal polymers are a new class of polymeric materials that consist of rigid backbone molecules and thus, even in the quiescent condition, take extended chain conformation to form optically anisotropic melts. A systematic investigation was carried out on how this type of material responds to two basic flow fields: shear and elongation. Rheological properties of the polymer in these flow fields have also been measured. It was found that a high level of molecular orientation was readily obtained by elongational flow but not with shear flow. Specifically, extraordinarily high orientation was obtained when the melt was subjected to small elongational strains, whiel shear strain or shear rate had little effect. A possible mechanism to explain these behaviors is illustrated based on the existing observations or theories of rodlike molecules. This finding was used to interpret the orientation distribution in the extruded and injection‐molded articles.
Orientation development in the injection molding of amorphous polymers
Authors: Isayev A. I.
Published: December 2004

Frozen‐in orientation in the injection‐molding of amorphous polymers has been considered in terms of flow‐ and cooling‐induced birefringence. In particular, measurements of the frozen‐in orientation distribution in polystyrene (PS) molded strips and circular runners have been performed. Three birefringence components, Δn, n22 − n33, and n11 − n33, have been measured for strips, and two components, Δn and nrr − nθθ, for runners. The effects of various processing conditions, of strip thickness, and of runner diameter on orientation development have been analyzed and compared with those predicted by our previously developed viscoelastic theory. In addition to injection‐molding experiments, free and constrained quenching experiments for PS and poly(methyl methacrylate) (PMMA) strips have been carried out and the gapwise distribution of cooling‐induced (thermal) birefringence has been measured. Relaxation of thermal birefringence following quenching has been observed for PMMA. The effects of flow‐ and cooling‐induced orientation on various components of birefringence in molded parts have been elucidated and limitations on the applicability of the stress‐optical law to the injection‐molding of amorphous polymers have been discussed.
Physical aging in polystyrene: Comparison of the changes in creep behavior with the enthalpy relaxation
Authors: Roe Ryong‐joon , Millman Gregg M.
Published: December 2004

Physical aging in polystyrene was studied by annealing samples isothermally (at 22°, 57°, and 93°C) for various lengths of time and measuring the changes in the enthalpy and the flexural creep property. The enthalpy decrease reached a constant value after about 10 hours of aging at 93°C, indicating an apparent attainment of equilibrium, whereas the creep behavior continued to change with prolonged aging even after 10 hours. At room temperature it took about a year of aging to induce a measurable change in enthalpy, while the creep behavior showed changes clearly only after hours of aging. These and other items of evidence indicate that the effect of aging on the creep behavior cannot be interpreted solely in terms of the free volume concept. Thus the hope of being able to predict the mechanical properties of aged polymers from the measurement of specific volume or enthalpy alone is not likely to be realized.
Properties of polyisobutylene‐polyurethane block copolymers: I. Macroglycols from ozonolysis of isobutylene‐isoprene copolymer
Authors: Speckhard T. A. , Strate G. Ver , Gibson P. E. , Cooper S. L.
Published: December 2004

The properties of a series of polyisobutylene (PIB) based polyurethanes were studied and compared to those reported in the literature for polyether, polyester, and polybutadiene‐based polyurethanes. Good phase separation was reflected in the invariance of the soft segment Tn with increasing hard segment content. Increasing hard segment content resulted in larger domains, higher modulus and lower ultimate elongation. The modulus above the soft segment Tn was higher than that previously reported for polyurethanes of similar hard segment contant; improved phase separation and short contour lengths of the PIB chains were cited as possible causes of this behavior. Stress‐strain data indicated a change from isolated to interconnected domain morphology with incerasing hard segment contant. Generally similar trends were seen for all types of urethanes. The overall properties of polybutadiene polyurethanes were closest to those of the polyisobutylene polyurethanes studied. The properties of both of these systems were suggested to suffer from significant synthesis problems in urethane formation due to the incompatibility of the nonpolar hydrocarbon soft segment and the polar diol chain extender. Preliminary environmental tests indicated that polyisobutylene based materials exhibit improved hydrolytic stability and reduced moisture permeability compared to polyether and polyester polyurethanes and greater oxidative stability compared to polybutadiene based materials.
Polyurethane‐poly(methyl methacrylate) interpenetrating polymer networks: Some mechanical properties
Authors: Morin A. , Djomo H. , Meyer G. C.
Published: December 2004

The mechanical behavior of polyurethane‐poly(methyl methacrylate) interpenetrating polymer networks (PUR/PAc IPN's) was investigated. Stress‐strain and impact resistance measurements were made on IPN's with a variable PUR content. The effect of the degree of crosslinking of each network on the mechanical properties was also studied. It appears that only the ultimate elongation varies largely upon changing the crosslink degree. The results are interpreted in terms of the contribution of each network to the mechanical behavior, but also by the interpenetration of both components and by the phase continuity of the PAc network.
Shear modification of polymers
Authors: Rudin Alfred , Schreiber Henry P.
Published: December 2004

Time dependence of recovery from shear history effects in polymer liquids can be used advantageously to modify the properties of macromolecules. The net result of shearing is a reduction in elasticity and possibly in viscosity of the polymer fluid. The material may be processed subsequently in a transient, less elastic, and less viscous state if the diffusion‐related rate of recovery of a more fully entangled equilibrium state is not too rapid. Shear‐induced changes in entanglement density are manifested in variations in die swell, die entrance pressure losses, normal stresses, melt strength, flow defects such as melt fracture and sharkskin surfaces, haze of extruded films, application properties of coatings liquids and, other properties. Evidence for shear‐modification effects is reviewed in this article. The polymer species that are most amenable to this treatment are identified in general terms; shear modification processes that have been used are summarized. Methods for augmenting the efficiency of mechanical shear modification include addition of plasticizers, fillers, and incompletely miscible polymers. The expedient mentioned last can be particularly effective. Assessments of the degree of shear modification are reviewed and applications to coatings mixtures are also summarized. The time‐dependent behavior of the type reviewed in this article limits the success of theoretical approaches, as in the application of constitutive equations to describe polymer‐liquid behavior. Attempts to relate Newtonian viscosities and other rheological parameters to polymer characteristics are similarly hindered when shear history effects are not taken into account.
Pressure dependence of newtonian viscosity
Authors: Utracki L. A.
Published: December 2004

Recently, a new method of generalization of the zero shear viscosity of liquids has been proposed. The method utilizes a modified Doolittle formula and the temperature‐dependent volume, as expressed by the corresponding states theory of liquids. Furthermore, the glass‐transition temperature has been employed as the scaling parameter. The proposed treatment allowed prediction of the correlation between: (i) viscosity, η, and temperature, T, (ii) η and the molecular weight of polymer, (iii) η and concentration, and (iv) the combined effect of these variables. At present, the method is extended to the pressure, P, effect. Furthermore, by substituting the free volume fraction in the Doolittle formula by the theoretical “hole fraction,” a master‐relation is proposed that provides means for predicting η = h(T, P) dependence.
Heat transfer and microstructure in extrusion blowmolding
Authors: Kamal Musa R. , Kalyon Dilhan
Published: December 2004

Experimental measurements were made to determine the contact temperature and the rate of heat transfer between the mold and the polymer during the cooling stage of the extrusion blowmolding process. The experimental data were compared to the results of a finite difference computer simulation of the heat transfer problem, allowing for the variation of the properties of the polymer in the solid and molten states. Good agreement was obtained between experimental and calculated results. Heat transfer results were subsequently employed to explain observed differences in the microstructure of the blowmolded articles, particularly in relation to the distributions of crystallinity and birefringence. Finally, it was demonstrated that much faster cooling rates and more uniform molded articles can be obtained by employing rapid internal cooling, as in the case of water injection into subzero air inside the inflated parison.
The hydrolytic stability of glass fiber reinforced poly(butylene terephthalate), poly(ethylene terephthalate) and polycarbonate
Authors: Kelleher P. G. , Wentz R. P. , Hellman M. Y. , Gilbert E. H.
Published: December 2004

The hydrolytic stability of glass fiber reinforced poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET) and polycarbonate (PC) was studied. The activation energies in kcal/mole for hydrolysis are 26 for PBT and 23 for PET. Both PBT and PET contain 30 percent glass fiber reinforcement. The hydrolysis rates for a series of experimental PC's containing 10, 30 and 40 percent glass were obtained from GPC data. These increase with glass concentration but are lower than that of the unreinforced PC. Melt flow rate changes are a good measure of the hydrolytic degradation of PET. However, in the time scale of these experiments, the tensile properties of glass reinforced PBT and PC do not correlate well with M̄w changes, unlike unreinforced PBT and PC polymers. Consequently, to compare these three glass fiber reinforced polymers, estimates of failure time must be based on changes in tensile strength rather than melt flow rate.
Distribution of striation thickness from impingement mixers in reaction injection molding
Authors: Baldyga J. , Bourne J. R.
Published: December 2004

The striation thickness distribution developed in an impingment T‐mixer is predicted using the statistical theory of turbulent diffusion. The predicted distribution is independent of the mixing nozzle Reynolds number, in agreement with some experiments, and is primarily a function of the mixing head geometry, the ratio of the reagent flow rates and the residence time distribution of the flow in the mixing head. Mixing is described as the result of fluid deformation in the intertial subrange of turbulent flow. The relationship of deformation to time and energy dissipation rate ϵ is examined. In the impingement T‐mixer ϵ is related to the kinetic energies of the streams entering and leaving the head. (There are no surface tension effects and pressure is relatively uniform in the mixing head, so that the kinetic energy is dissipated by viscous forces.) The distribution of residence times of fluid elements in the T‐mixer is responsible for varying degrees of deformation and hence a distribution of striation thickness. This residence time distribution does not seem to have been studied and the flow pattern was thus modeled as perfect macromixing, having an exponential distribution. The procedure developed in this paper to calculate the distribution of striation thickness allows reasonable estimates of its parameters from fluid mechanical information and showed good agreement with experimental values, without having to fit any quantities. This new approach to striation thickness distribution is worth further evaluation.
Effects of axial stretching on the resistivity of carbon black filled silicone rubber
Authors: Kost J. , Narkis M. , Foux A.
Published: December 2004

The resistance and resistivity of Ketjenblack EC/silicone rubber compounds were studied as function of strain in constant strain rate experiments. Both strain and rate of strain affect the electrical resistivity of the compounds. Such effects are carbon black concentration dependent. Ketjenblack EC, a low structure black, is shown to behave differently than other blacks of high structure in the electrical resistivity‐strain experiments. The resistivity in the straining experiments is determined by the transient distribution of the conductive particle array.
Melt rheology of polymer blends the morphology feedback
Authors: Plochocki A. P.
Published: December 2004

Particular rheology compositions (PRC) so far observed for blends of polyolefins are confirmed with composition dependence of melt elasticity and viscosity functions for polypropylene/rubbers and blends of other commercial polymers. Particular morphology at PRC was indirectly ascertained from the composition dependence of specific volume, vT–compositions for which the maximum vT observed are those of minimum viscoelasticity. Direct evidence from scanning electron microscopy (SEM) indicates that the disperse morphology undergoes distinct change at PRC: from uniform into bimodal, with coarser core. Rubber rich mixtures display stratified texture confirming that the melt elasticity ratio (Van Oene's) criterion for disperse/stratified morphology transition is valid in case of polypropylene/rubber blends. For a set of polymers of given melt elasticity ratios and at a composition ratio, static and rotational distributive mixers generate polyblends differing significantly in the melt rheology—morphology interaction.
NMR characterization of intermolecular interactions for polymers, IV. Intermolecular interactions of low molecular weight analogues for compatible blends of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Djordjevic Miomir B. , Porter Roger S.
Published: December 2004

The intermolecular interaction, IMI, leading to the compatibility of polystyrene, PS, and poly (2,6‐dimethyl‐1,4‐phenylene oxide), PPO, has been identified by analyzing the IMI of the model compounds of low molecular weight; cumene, styrene oligomer, 2,6‐dimethyl phenol, and its trimer. The IMI has been detected and identified applying Rummens' method for the analysis of the solvent‐induced changes in NMR chemical shifts. The results indicate that the driving force in the formation of the compatible blend of PS and PPO is the π‐hydrogen bond between the electrodeficient methyl groups in PPO and π‐orbitals in PS. There were no indications that n‐hydrogen bonds are formed between ring hydrogens of PS and the oxygen in PPO.
Stress‐relaxation crazing of polymers — an energy criterion
Authors: Brueller O. S.
Published: December 2004

One of the most important signs of failure, easily observable in transparent and translucent polymers, is the appearance of visible crazes. The observation of first crazes is relatively simple in uniaxial long‐term experiments (such as creep and stress‐relaxation). An energy‐related crazing criterion has allowed good predictions of the appearance of first visible crazes under uniaxial creep loading conditions. The results have shown that in spite of the different applied stresses and different corresponding crazing times, the specific dissipated energy at crazing was the same. The objective of the present work was to investigate if this criterion, based on the constancy of the specific dissipated energy, is valid also for uniaxial stress‐relaxation. The good agreement between theoretical predictions and experimental results confirms this assumption.
The apparent rate constant model for kinetics of radical chain copolymerization: Chemical‐controlled process
Authors: Kuo Jen‐Feng , Chen Chuh‐Yung , Chen Chun‐Wen , Pan Ting‐Chung
Published: December 2004

In this article the kinetics of chemical‐controlled radical‐chain copolymerization have been reduced to pseudohomopolymerization kinetics by introducing the apparent rate constants, The methods for the determinations of the values of the apparent rate constants, mode of termination, and the methods for the calculation of molecular weights and distributions are proposed. The data required for these determinations and calculations are simply obtained by the usual steady‐state method. According to the traditional kinetics along with the definitions of the apparent rate constants, these apparent rate constants as functions of traditional rate constants, monomer compositions, and copolymer compositions are derived. Further utilizing the theoretical expressions obtained, we show that the apparent rate constants are the general rate constants for both radical chain homo‐ and copolymerizations. The bulk radical copolymerizations of methyl methacrylate and styrene at various monomer feed compositions at 60°C are used to test the proposed model. The empirical apparent rate constants obtained are described well, by the following expressions,

and

and the mode of termination on the combination termination is

where K and K denote the apparent rate constants of propagation and termination, respectively. The term f1(= 1 − f2) stands for the mole fraction of styrene in the monomer solution fed. F1 is the copolymer composition produced at f1. β is the mode of termination.
Modeling of polyethylene terephthalate reactors: 7. MWD considerations
Authors: Ravindkanath K. , Mashelkar R. A.
Published: December 2004

A mathematical model has been developed to compute the molecular weight distribution (MWD) in the polyethylene terephthalate (PET) manufacturing process. Unlike the previous efforts, this model takes into account the influence of side reactions and various interchange reactions on MWD. The process of blending of molten polyester chips has also been simulated with a view to calculate the equilibrium MWD as well as the time required to reach the equilibrium MWD. The1 significance of the results has been discussed in terms of industrial operations involving PET polymerization and PET blending.
Theoretical investigations on some rigid‐rod polymers used as high‐performance materials
Authors: Welsh William J. , Bhaumik Dharmajyoti , Jaffe Hans H. , Mark James E.
Published: December 2004

This review focuses on a new type of para‐catenated aromatic polymer being used in the preparation of high‐performance films and fibers of exceptional strength, thermal stability, and environmental resistance, including inertness to essentially all common solvents. Polymers of this type include cis and transpoly(p‐phenylene benzobisoxazole) (PBO), and the cis and trans forms of the corresponding poly(p‐phenylene benzobis‐thiazole)(PBT). The purpose of this paper is to summarize the authors' theoretical work on the structures, conformational energies, intermolecular interactions, and electronic properties of PBO and PBT chains, including the protonated forms known to exist in strong acids. The emphasis is on how such studies provide a molecular understanding of the unusual properties and processing characteristics of this new class of materials.
Linear‐low‐density polyethylene melt rheology: Extensibility and extrusion defects
Authors: Constantin D.
Published: December 2004

This paper investigates three aspects of linear‐low‐density polyethylene (LLDPE) rheological properties: shear viscosity variations with shear rate and temperature, tensile behavior determined with an extensiometer, and extrusion defects. The differences in shear viscosity variation with shear rate and temperature between LLDPE and LDPE (low‐density polyethylene) are shown. These differences, attributed to wider molecular weight distribution and to long chain branching (LCB) in LDPE, involve different extrusion behaviors. The lack of LCB in LLDPE can be demonstrated by comparison of the measured Newtonian viscosity with the value of the same parameter calculated from molecular weight distribution and composition law of Newtonian viscosities. The lack of LCB leads to good melt extensibility, which is shown by tensile properties of polyethylene melts determined with a non‐isothermal extensiometer. The melt fracture phenomenon is studied because it promotes surface defects on bubbles in film application. Extrudate distortions are examined at the laboratory extruder outlet. This test shows differences between LLDPE and LDPE, but also between some LLDPE samples.
The influence of high storage humidity on some properties of solid propellants
Authors: Harniv Israel , Rigbi Zvi
Published: December 2004

The absorption of water vapor by propellants based on hydroxy‐terminated polybutadiene and an isocyanate from atmospheres of increasing relative humidities, and the swelling index of the propellant which had absorbed various proportions of water, were measured in an attempt to establish the extent of hydrolytic damage. The method was found incapable of assessing such damage, but it was shown that there was no measurable absorption of vapor below 92 percent relative humidity (RH). The MEK/polymer and toluene/polymer interaction parameters were determined.
Gas chromatographic determination of the interaction parameter of poly(ethylene oxide)/poly(methyl methacrylate) blends
Authors: Elorza J. M. , Fdz‐Berridi M. J. , Iruin J. J. , Guzman G. M.
Published: December 2004

Inverse gas chromatography (IGC) has been used to investigate thermodynamic miscibility of a molten poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blend. Toluene, benzene, and chloroform have been employed as probes in pure and mixed stationary phases of these polymers. Experimental measurements have been taken over a narrow range of temperatures because of the high PMMA glass transition temperature as well as the degradation of the PEO. The interaction parameter χ23 determined at 150°C is slightly negative and dependent on the interacting probe, as has been also noted in previous chromatographic studies on polymer‐polymer miscibility. The last section is devoted to a model calculation, using Flory's equation of state theory. Different χ23‐concentration curves have been simulated, with the interaction energy parameter X23 as an adjustable parameter.
Chain scission and mechanical degradation of polystyrene
Authors: Fordyce P. , Devries K. L. , Fanconi B. M.
Published: December 2004

The extent of molecular degradation of amorphous polystyrene when subjected to mechanical grinding at cryogenic temperature has been investigated using electron spin resonance, infrared spectroscopy, and viscometry. Essentially identical concentrations of chain ruptures in the degraded samples were found from infrared spectroscopic determinations of molecular end group concentrations and by the changes in the viscosity‐average molecular weights. The chain‐scission concentration was from two to four times the free‐radical concentrations, indicating that free‐radical‐propagation reactions play a much less dominant role in the degree of molecular damage associated with mechanically induced chain scission in glassy polymers. In addition, experiments were carried out as a function of molecular weight and these indicated a virtual independent behavior with molecular weight.
High‐temperature electrical conductivity and thermal decomposition of Sylgard® 184 and mixtures containing hollow microspherical fillers
Authors: Johnson R. T. , Biefeld R. M. , Sayre J. A.
Published: December 2004

The high‐temperature electrical conductivity and thermal decomposition characteristics of Sylgard® 184 with and without hollow microspheres of glass, silica, and ceramic have been determined to 600 to 700°C in air and nitrogen environments. The materials are silicone‐based dielectrics and are used as electronic encapsulants. Results show that a peak in the conductivity temperature dependence at ∼300°C results principally from volatilization of [Si(CH3)2O]n with some evolution of water, that oxygen accelerates decomposition, and that the microspheres may help form a network of interconnected conductive pathways in the residual material. There is a good correlation between thermal stability and temperature‐dependent electrical properties.
Mechanical compatibilization of immiscible blends
Authors: Barlow J. W. , Paul D. R.
Published: December 2004

The mechanical properties of a variety of immiscible binary blends, with and without third component polymeric compatibilizers, are reviewed and qualitatively related to the degree of adhesion between blend components as determined by lap shear testing. Generally, blends comprised of components which adhere well, one to the other, show improved ductility relative to blends of components which do not adhere, Similarly, polymeric compatibilizers are found to be more effective for improving the properties of a binary blend system if they adhere well to both primary components of the immiscible mixture. These results suggest that adhesion between phases in the mixture strongly influences the ultimate properties of the blend. Some evidence is presented which suggests that components which adhere well are partially miscible.
Polypropylene based polymer blends: Fields of application and new trends
Authors: Galli P. , Danesi S. , Simonazzi T.
Published: December 2004

The new industrial strategy in the polymer field requires the transformation of plastic “commodities” into “specialties”. From this point of view, polypropylene (PP) plays an important role both for its intrinsic properties such as high melting temperature, low density, high chemical inertness and for its capability to be produced with different morphological and molecular structures, to be modified with the addition of other polymers or mineral fillers and to be grafted with functional groups. The present range of special and reinforced polypropylene grades includes: elastomer‐modified PP, elastomer‐modified filled PP, glass fiber‐reinforced PP, filled PP, esthetic filled PP, flame‐retardant PP, and thermoplastic elastomers. New trends for significantly improving this family of polymers involve impact resistance, processability, durability, dimensional stability, elasticity, and surface properties. A positive answer to this complex emerging demand will put, as indicated, in this work, “special and reinforced polypropylene grades” in a position to successfully compete with technopolymers in some important, rapidly growing application sectors.
Roll fusing of toner particles on rough papers in the xerographic process
Authors: Kuo Youti
Published: December 2004

This paper deals with squashing of toner particles in a variety of paper topographies in the roll fusing of toner images in xerographic machines. The model developed can be used for predicting the mean spreading ratio of toner particles related to fix level with given rheological properties and fusing temperature and pressure.

The deformation of toner particles is solved with respect to the asperity pressure encountered in the contact between the roll and the paper surfaces. Various contact situations are considered, among them: toners on smooth papers, on tops of paper asperities, and at valleys of a paper surface. In addition to rheological properties and fusing conditions, toner spreadings also depend on toner size, paper roughness, and the rubber modulus of the fuser roll.

Based on an integration algorithm, statistical averages of toner spreadings can be computed in terms of distribution functions of toner and paper asperity height. Comparisons of theoretical predictions with measurements show good agreement over a broad range of data.
Heat transfer in injection molding of crystallizable polymers
Authors: Kamal M. R. , Lafleur P. G.
Published: December 2004

A model is proposed for the treatment of heat transfer with crystallization during plastics processing in general, and injection molding in particular. The model incorporates experimentally determined crystallization kinetics parameters. It permits the calculation of the distribution of both temperature and crystallinity in the molding. Theoretical predictions are in good agreement with experimental measurements in both injection molding and a prototype apparatus.
Compatibilization of polyester/polyamide blends via catalytic ester‐amide interchange reaction
Authors: Pillon L. Z. , Utracki L. A.
Published: December 2004

In a series of publications we reported on melt rheology, morphology, and mechanical properties of the poly(ethylene terephthalate)/poly(amide‐6,6) blends (PET/PA). The non‐oriented samples had poor interphase bonding resulting in low impact and tensile strengths. To improve these properties the ester‐amide interchange reaction was carried out in solution and in melt. In the latter case a Brabender Plastograph was used in the mixing chamber or twin‐screw extruder configurations with p‐toluenesulfonic acid as a catalyst. The interchange reaction was followed by 400 MHz proton and 13C nuclear magnetic resonance spectroscopy.
Development of phase morphology in incompatible polymer blends during mixing and its variation in extrusion
Authors: Min Kyonsuku , White James L. , Fellers John F.
Published: December 2004

An experimental study of the development of phase morphology in incompatible polymer melt blends of polyethylene/polystyrene (PE/PS), polyethylene/polycarbonate (PE/PC), and polyethylene/nylon‐6 (PE/N6) is presented. Different temperatures (180°C, 240°C) of mixing and polyethylene molecular‐ weight levels were used in the PE/PS studies. Little variation in the cross‐sectional phase morphology of the PE/PS extrudates was observed with these variables, though the morphology became finer with increased shear rate/stress in capillary die flow. Variations in the longitudinal morphology are observed with continuous filaments of dispersed phase only arising when the dispersed phase has an equal or lower viscosity than the continuous phase. The PE/N6 and PE/PC, especially the former, give coarser morphologies when the N6 and PC are the continuous phases. This was attributed to larger inter‐facial tensions. The effect of viscoelasticity was also discussed.
A basic study of orientation in poly(ethylene terephthalate) stretch‐blow molded bottles
Authors: Cakmak Mukerrem , Spruiell Joseph E. , White James L.
Published: December 2004

A series of stretch‐blow molded poly(ethylene terephthalate) bottles were investigated using measurements of birefringences (in plane and out of plane) and wide angle x‐ray diffraction (WAXS) pole figures. Both bottles prepared in our laboratories and commercial bottles were investigated. Birefringences Δn13 and Δn23 of inside and outside surfaces of bottles were determined as a function of position along the length of the bottle (1‐bottle axis, 2‐hoop direction, 3‐thickness direction). The Δn13, Δn23 for the inside surface of the bottles were found to be greater than those for the outside surface indicating heterogeneity through the thickness of the bottles. The WAXS studies indicate that the benzene rings in the polymer align parallel to the bottle surface. The chain axis in crystalline regions exhibit orientations close to equal biaxial orientation. Both Δn13 and Δn23 increased with inflation pressure.
Predicting water diffusivity in elastomers
Authors: Aminabhavi Tejraj M. , Thomas Richard W. , Cassidy Patrick E.
Published: December 2004

By the use of water absorption data (rate and equilibrium), the diffusivity of distilled and salt water through Neoprene, styrene‐butadiene, and ethylene‐propylene‐diene elastomers was predicted. Activation parameters were calculated from the Arrhenius plots and were used to calculate heats of solution (all negative). Solubility coefficients (S) were calculated from permeability (P) and diffusion (D) coefficients. For all materials salt water showed a lowerDthan distilled water but a higherSandP.
Polycarbonate resins
Authors: Clagett Donald C. , Shafer Sheldon J.
Published: December 2004

An outline of the history and manufacture of polycarbonate resins is followed by a discussion about resin product types anal their processing. The key properties of flex modulus, deflection temperature, and impact are those that make polycarbonate resins premier engineering resins. Like most other engineering plastics, polycarbonate resins' early commercial history was characterized by substitutions of polycarbonate resins for traditional materials, particularly metal and glass. Examples of applications are presented, More recently application developments involve ab initio selection of polycarbonate resins and article designs based on polycarbonate resin properties. In addition, “tailored” resins such as poly (estercarbonate) resins and polycarbonate resin blends have evolved to meet specific applications. The future growth of polycarbonate resins is predicted to feature few new resins, many new blends, and application developments using computer techniques.