bluuebunny/crossref_metadata_2025 huggingface dataset:
The properties of mica‐filled polypropylenes
Authors: Busigin C. , Lahtinen R. , Martinez G. M. , Thomas G. , Woodhams R. T.
Published: December 2004

Water‐ground Phlogopite micas were classified into narrow particle‐size distributions containing flakes with well‐defined diameters and thicknesses in order to evaluate the influence of particle size and flake aspect ratio on the mechanical properties of mica‐filled polypropylenes, For the purposes of comparison, most of the injection‐molded specimens contained 40 percent (by weight) mica. As expected, the flexural and tensile modulus values increased in proportion to the aspect ratio over the range from 30 to 60 to a maximum of 8 GPa. The measured tensile strengths of the mica‐filled polypropylenes increased substantially as the flake diameter became smaller, but did not correlate with the flake aspect ratio. The attainable properties were frequently dependent upon the method of mixing, and considerable care was necessary to ensure proper dispersion and adequate coupling. Intensive mixing, as in a Gelimat Mixer, may cause in situ delamination and particle‐size reduction of the mica filler particles, leading to a marked increase in tensile strength of the resulting composite. The mica‐filled compounds could be reprocessed many times without significant loss of properties, particularly compounds having mica particles less than 40 μm in diameter. The fracture energies (notched Izod) and the heat‐distortion temperatures were not appreciably influenced by the size or aspect ratios of the mica within this range. Increased fracture toughness could be achieved by reducing the mica concentration or employing a polypropylene copolymer. Guidelines are presented to indicate the preferred characteristics of mica fillers and the influence of mixing conditions on performance.
Optimization of the transesterification stage of polyethylene terephthalate reactors
Authors: Kumar Anil , Sukthankar V. K. , Vaz C. P. , Gupta Santosh K.
Published: December 2004

The tranesterification step of the polyethylene terephthalate (PET) formation consists of several side reactions in addition to the main ester interchange, transesterification, and polycondensation reactions. The side reactions considered in this work are acid end group, acetaldehyde, diethylene glycol, water, and vinyl end group formations. The objective function of the batch esterinterchange reactor is assumed to consist of maximizing the conversion and simultaneously minimizing the formation of side products. The control vector iteration procedure has been used to optimize the esterinterchange reactor and the temperature‐time profile that gives the best performance has been found. It is found that the reactor should be operated at a high temperature initially to obtain high conversion of dimethyl terephthalate (DMT) first, but then it should be lowered to reduce the formation of side products.
Solution of final stages of polyethylene terephthalate reactors using orthogonal collocation technique
Authors: Kumar Anil , Gupta Sushil K. , Madan Sanjiv , Shah Nirmal G. , Gupta Santosh K.
Published: December 2004

The formation of polyethylene terephthalate (PET) has been modeled to have reactions with monofunctional compounds, redistribution, and cyclization reactions in addition to the usual polycondensation step. In the final stages, the overall polymerization is mass‐transfer controlled and solution of the reactor performance equations have been determined through the orthogonal collocation technique. This technique is found to be considerably more efficient for PET reactors compared to the finite difference method; the use of ten collocation points gives results which are close to the exact solution.
The effect of a temperature gradient on residual stresses and distortion in injection moldings
Authors: Thompson M. , White J. R.
Published: December 2004

Distortion of bars injection‐molded from polystyrene, polypropylene, and glass‐fiber‐filled polypropylene and subsequently placed in a temperature gradient has been examined. Residual stress distributions have been measured both for the as‐molded state and after annealing in a temperature gradient. In the as‐molded state all moldings showed the usual residual stress distribution with compressive stresses near the surface and tensile stresses in the interior. In all three materials it was found that tensile stresses could be developed near to the warmer surface on gradient annealing and that tensile stresses still remained at this surface when the bar was cooled and permitted to bend to restore internal equilibrium. It is shown therefore that in addition to the dimensional changes which occur and which may render the molding unserviceable after temperature gradient annealing, another undesirable change takes place, leaving the molding much more susceptible to fracture from a surface flaw. Uniform annealing is found to be much less likely to cause stress reversal and the stresses remain balanced so that distortion is minimal.
Necking behavior of low‐density polyethylene‐isotactic polypropylene blends: A morphological investigation
Authors: Rizzo Giovanni , Spadaro Giuseppe
Published: December 2004

The tensile behavior of low‐density polyethylene‐isotactic polypropylene blends was investigated at room temperature. Neck formation and propagation along the whole length of the samples were observed for the whole range of composition. This behavior, which is not indicated by most data available in the literature, was examined in relation to sample morphology by scanning electron microscopy. The results of this investigation indicated some differences between the morphology of these materials and the morphology of blends which do not undergo necking propagation.
Microphase structure and properties of polyurethane/polyvinyl interstitial composites
Authors: Koberstein Jeffrey T. , Stein Richard S.
Published: December 2004

The morphology of two series of polyurethane/polyvinyl interstitial composites is characterized by scanning electron microscopy, small‐angle light scattering, and small‐angle X‐ray scattering. Thermal and mechanical properties are measured using differential scanning calorimetry and dynamic mechanical analysis. The polyurethane networks examined are microphase separated segmented block copolymers. A variety of linear and network vinylic components are studied including polymethacrylonitrile homopolymer and copolymer, and polyacenaphthalene homopolymer and copolymer. The polyurethane and polyvinyl components phase separate during the in situ polymerization resulting in a three‐phase morphology. Detailed small‐angle X‐ray scattering analysis provides measurements of phase mixing, domain spacings, and diffuse phase boundary thicknesses. A comparison of these parameters for parent polymers and composites reveals only slight differences; indicating that the microdomain structures of the phase‐separated polyurethane networks are preserved in the composite. Appreciable molecular interpenetration of components is not observed. Dynamic mechanical loss measurements for several of the composites demonstrate the presence of loss processes occurring over extremely broad ranges of temperature. The strong mechanical interaction between components observed suggest that the urethane and vinyl phases may be bicontinuous in these materials.
The crystalline morphology of poly(vinylidene fluoride)/poly(methylmethacrylate) blends
Authors: Morra B. S. , Stein R. S.
Published: December 2004

Poly(vinylidene fluoride), PVF2, as well as blends of PVF2 with poly(methyl methacrylate), PMMA, develop a variety of crystalline morphologies at low undercoolings. Both the α and γ crystal forms grow from the melt and the former undergoes a solid‐solid phase transition to the latter, though its morphology remains unaltered. Three melting temperatures which decrease with increasing PMMA content are observed. Hoffman‐Weeks analysis shows the equilibrium melting points of the blends to be depressed. Using these equilibrium values, the thermodynamic interaction energy density is calculated to go from −5.40 × 106 to −2.96 × 107 j/m3 as the blend composition goes from 40.1 volume percent to pure PVF2. The band periodicity in the α form spherulites increases with crystallization temperature and PMMA content and it appears to be from a lamellar reorientation process with an apparent activation energy of 322 cal/mole. Electron diffraction patterns taken along the radial direction in a given spherulite reveal lamellar twisting which causes the banded appearance. Light scattering results suggest that the lamellar are formed into rod‐like structures on a local scale but that on a larger scale they develop a disoriented spherulitic morphology.
Performance of gear pumps in polymer processing
Authors: McKelvey James M.
Published: December 2004

Within the past several years considerable interest has developed in the practice of retrofitting plasticating extruders with gear pumps. The primary motivation for this is to reduce surges and fluctuations in the extrusion rate, thereby improving product quality and reducing waste. It is shown that the effectiveness of a gear pump for this purpose is directly related to its volumetric efficiency, which depends upon the pump dimensions, the flow behavior of the polymer, and the operating variables of temperature, pressure differential, and pump speed. Experimental data on three thermoplastic materials using a pump having gear wheels of 36 mm diameter for both leakage and power are reported. These data have been correlated with semi‐empirical equations.
Experimental study and computer simulation of a two‐stage continuous polymerization process for the production of methyl methacrylate
Authors: Carratt G. M. , Shervin C. R. , Soong D. S.
Published: December 2004

The two major problems encountered in industrial liquid‐phase addition polymerization are: the heat released by highly exothermic reactions and the great increase in viscosity with conversion. The high rate or heat generation, coupled with the low thermal diffusivity of the reacting system, often lead to thermal runaway. Even with the process kept under marginal control, large temperature variations broaden the product molecular‐weight distribution. Temperature control is particularly difficult in the Trommsdorff region, where reaction rate rapidly increases as temperature rises and viscosity builds up. A two‐stage process is developed in this work to attack these problems and to achieve continuous operation of poly(methyl methacrylate) bulk polymerization. This process utilizes a continuous stirred‐tank reactor (CSTR) as a first‐stage prepolymerizer and a spray tower as the second‐stage finishing reactor. Use of a CSTR offers good temperature control and product uniformity during the early stages of reaction and eases delivery of the reacting system to the second stage at the desired conversion and molecular‐weight level. Spraying the partially polymerized mixture into the tower as fine droplets prior to the onset of gel effect eliminates the problems of transporting, agitating, and mixing a reacting system with a rapidly increasing viscosity. Heat of reaction is efficiently removed by a countercurrent stream of nitrogen in the tower, in direct contact with the falling droplets. The high surface‐to‐volume ratio of these small droplets facilitates heat transfer, and the problem of heat buildup can be efficiently controlled. Products from the bottom of the tower can then be melt‐processed by conventional methods, such as extrusion. Experiments performed in the laboratory have demonstrated the feasibility of this proposed concept. Process optimization was in no way achieved due to serious space and equipment limitations. The process was thus further examined by computer simulation and model parameter sensitivity study. A practical design was recommended based on the model predictions.
An experimental study on the injection molding of thermosetting polyester resin
Authors: Han Chang Dae , Lem Kwok‐Wai
Published: December 2004

An experimental study was conducted on the injection molding of a thermosetting polyester resin. For the study, a general‐purpose unsaturated polyester resin was used, with benzoyl peroxide as initiator. A differential scanning calorimeter (DSC) was used for studying the curing kinetics, under isothermal curing conditions. A plunger‐type injection‐molding apparatus was constructed, and a rectangular mold cavity with glass windows on both sides was constructed, which permitted us to record on a film the changes in stress birefringence patterns in the mold cavity during the molding operation (i.e., during the isothermal cure, post cure, and subsequent cooling), using a crossed circular polariscope. The injection‐molded specimens were used to determine the distribution of the degree of cure at various positions in the flow direction, and to relate the degree of cure to the dynamic mechanical properties.
A novel hysteresis test for studying crazing and shear yielding in rubber‐toughened polymers
Authors: Bucknall C. B. , Marchetti A.
Published: December 2004

Tensile, tensile impact, compact tension, and fatigue tests were carried out on ABS (acrylonitrile‐butadiene‐styrene), HIPS (high impact polystyrene), and toughened PMMA (poly(methyl methacrylate)). Dumbbell specimens machined from test pieces were then subjected to sinusoidal tension‐compression cycling at low stress amplitudes. The HIPS specimens produced asymmetrical hysteresis loops characteristic of multiple crazing, whereas PMMA gave more symmetrical, regularly shaped, loops. The behavior of the ABS polymers varied with loading history. It was concluded that the hysteresis test provides a useful additional technique for studying deformation mechanisms, especially under conditions that do not readily permit volumetric measurements.
Binary blends containing a commercial polyarylate
Authors: Eguiazábal J. I. , Calahorra M. E. , Cortázar M. M. , Iruin J. J.
Published: December 2004

A commercial polyarylate (PAr), a copolyester of Bisphenol‐A with 50 percent terephthalate‐50 percent isophthalate, has been characterized by means of a combination of gel permeation chromatography and viscometry. It has been studied as first component of a series of polymer blends. The presence of either one glass transition temperature (Tg) or two has been used as a criterion to determine the miscibility of each blend. In some cases, the possible incidence of transesterification reactions has been considered.
Morphology and properties of blends of polypropylene with ethylene‐propylene rubber
Authors: Yang Decai , Zhang Bailan , Yang Yongkuan , Fang Zheng , Sun Guifen , Feng Zhiliu
Published: December 2004

Great attention has been paid to the toughening of isotactic polypropylene (PP) in recent years in order to make full use of this plastic. This paper presents the results of our study on the compatibility of PP with ethylene‐propylene‐diene rubber (EPT), polybutadiene rubber (PB) or styrene‐butadiene rubber (SBR) through characterization of the blends' morphology, and on. the morphology and properties of binary blends of PP with EPT (EPT/PP) and ternary blends of PP, EPT, and polyethylene (PE) (EPT/PE/PP). Morphological structure of solution blends and the great improvement in low‐temperature impact strength and other properties of the mechanical blends have shown the difference among EPT, PB, and SBR in compatibility with PP, the effectiveness of using EPT as PP's toughening agent, and the effect of EPT on EPT/PP blend as both toughening agent and compatibilizer. Addition of EPT to EPT/PP made interesting changes in morphology but no effect on properties was observed.
Common structure, compatibility and complementarity of mathematical models of injection molding
Authors: Grmela Miroslav
Published: December 2004

The hierarchy of mathematical models of injection molding is reviewed. Compatibility of the models of the hierarchy, usefulness of simultaneous applications of models formulated on several different levels of the hierarchy and compatability between physical approximations leading to the formulation of a model, and mathematical approximations used to solve numerically the governing equations of the model are discussed. This review is intended to facilitate the search for a model that is best suited to a given need and to indicate future research.
Permeability of oxygen and water vapor through polyethylene/polyamide films
Authors: Kamal M. R. , Jinnah I. A. , Utracki L. A.
Published: December 2004

Oxygen and water vapor permeability studies were carried out on binary polyethylene/polyamide immiscible blends incorporating three polyethylene resins (LDPE, LLDPE, and HDsPE), and three polyamide resins (PA‐6, PA‐6,6, and modified PA‐6,6m). It was found that the incorporation of PA into PE reduces the oxygen permeability while water vapor permeability is increased. In the range of 0 to 30 weight percent of PA, the oxygen permeability of PE was reduced by a factor of 2.8 to 3.6. Maximum water vapor permeabilities increased: for HDPE by a factor of about 2.6 to 3.1 and for LDPE and LLDPE blends by about 1.6.
Ultrasonic velocity measurement for the determination of density in polyethylene
Authors: Piché L.
Published: December 2004

An ultrasonic immersion method is presented for the rapid and accurate measurement of longitudinal sound velocity (v) in polyethylene (PE). The method is based solely on the measurement of time delays and can be automated. The samples are the same press‐molded plaques that are prepared for the standard‐density (ρ) determination using a density‐gradient column, Our measurements on a representative group of various types of PE with densities in the range 0.92 to 0.96 g/cm3 show without ambiguity that v is proportional to ρ. The degree of correlation is such that we come to suggest that the acoustic method be used for the characterization of density. We show that the accuracy is good and compares with that of the density‐gradient column and we then conclude on the practical advantages of the ultrasonic method.
Unsaturated polyester based on poly(ethylene glycol)
Authors: Tong S. N. , Chen D. S. , Kwei T. K.
Published: December 2004

Unsaturated polyesters were prepared by one‐stage melt condensation of maleic anhydride, phthalic anhydride, propylene glycol, and poly(ethylene glycol)s with different molecular weight, and the properties of their castings from styrenated resins were investigated. Tensile and flexural properties decrease with the increase of molecular weight of poly(ethylene glycol), but impact strength, elongation, and water absorption have an inverse effect. This study improves the understanding of the effect of chain length of poly(ethylene glycol) in unsaturated polyester on the properties of its castings.
Two and three component interpenetrating polymer networks
Authors: Klempner D. , Frisch K. C. , Xiao X. H. , Frisch H. L.
Published: December 2004

Two and three component interpenetrating polymer networks (IPNs) have been prepared from polyurethanes, epoxy resins, and acrylic copolymers using the simultaneous technique (SIN). These materials exhibited a variety of morphologies and properties dependent on the types of polymer, molecular weight of precursors, presence of charge groups, and presence of intentional grafts between the component polymer networks. In general, decreasing molecular weight of prepolymers, presence of intentional grafts, and presence of charge groups of opposite charge resulted in increased homogeneity (interpenetration). In addition, increased homogeneity resulted in enhanced mechanical properties.
Processing of reinforced plastics using multi‐screw compounders
Authors: Eise Kurt , Curry John , Farrell John
Published: December 2004

Polymer modification by addition of reinforcing agents represents a popular means of increasing physical property values. The polymer matrix has been forced to accept up to 55 percent by weight of fibrous reinforcement and 80 percent by weight of powdered types in order to meet application requirements. These materials demand sophisticated mixing equipment which must provide extensive intake and conveying capabilities, polymer wetting of reinforcement, and dispersion of reinforcement. This process must also be conducted with controlled shear intensity and excellent temperature and residence time control in order to respect polymer thermal sensitivity and product requirements. The extrusion process is a proven economical method for incorporating reinforcements into polymer resins. Co‐rotating intermeshing twin‐screw extruders are particularly suited for these tasks. Positive conveying, self‐wiping, and shear intensive mixing characteristics provided by the screw mechanism satisfy requirements of reinforcement compounding. This mechanism allows interruption of streamline flow which is needed to disperse both high and low aspect ratio reinforcing agents into a polymer matrix. Mathematical representation of the benefits of twin‐screw extrusion (relative to single‐screw) related to pumping and mixing capability have been developed based on the classical pressure flow continuity equation with proper selection of boundary conditions.
Hydrodynamic analysis of negative flow in a spiral disc extruder
Authors: Krein H. L. , Plumtree A. , Rudin A.
Published: December 2004

The flow of polymer melts in a rotating disc extruder is analyzed with a mathematical model for pressure flow and leakage flow (termed neg ative flow). It is assumed that the material is fully melted and exhibits Newtonian flow behavior under isothermal conditions for each element. Flow is evaluated in successive sections of the flow path and the final expression involves a computer‐assisted numerical solution. Pressure flow, which is negative, is calculated by analyzing the situation in which the pressure gradient causes the extrudable material to flow back across the stationary disc. A simplified geometrical model is developed for numerical solution, assuming incompressible flow. Leakage flow is between the contours of the disc and the engaging interior face of the housing. The flow is also directed opposite to the drag component and is estimated by using parallel plate flow equations.
On the nonlinear response of polymers to periodical sudden loading and unloading
Authors: Brueller O. S.
Published: December 2004

In practice, it happens very often that structural parts made of plastics are submitted to a long term loading which “jumps” periodically between a constant maximal value and a constant minimal one. The knowledge of the material response to such a kind of loading demands very laborious experimental investigations. Since generally the loading takes place in the nonlinear viscoelastic range of the material, an analysis based on linear superposition cannot be applied. In the present paper a computational method is proposed to predict the response of the polymer to a low frequency “jumping” load in the nonlinear viscoelastic range, This method is based on the knowledge of the long term behavior of the material under constant loading conditions, which is approximated by finite exponential series. Both cases, stress‐relaxation‐type and creep‐type loading histories are treated. Examples presented show a very good agreement between theoretical predictions and experimental data.
A computer study of film blowing
Authors: Luo X‐L , Tanner R. I.
Published: December 2004

This paper extends Petrie's work on film‐blowing to cover viscoelastic non‐isothermal flow for both the convected Maxwell and the Leonov models. Good agreement with experimental data is shown for the former. The calculations are highly unstable, however, and it is difficult to obtain convergence with arbitrary values of the film‐blowing parameters. The general effect of viscoelasticity is to stiffen the film and restrain the increase in bubble diameter. There is some difference between bubble shapes generated using the Maxwell and Leonov constitutive models but the temperature variation of properties is seen as the dominant effect, The Leonov model tends not to be stiff enough in its response to the present flow, which is purely extensional and good agreement with experiment was not obtained. For the Maxwell model the relevant mean relaxation time must be used for good agreement between experiment and calculation.
The rubber particle size dependence of crazing in polypropylene
Authors: Jang B. Z. , Uhlmann D. R. , Sande J. B. Vander
Published: December 2004

The tensile crazing and Charpy impact behavior of polypropylene modified with styrene‐butadiene copolymer (SBR) and ethylene‐propylene‐diene monomer (EPDM) was studied. Various rubber particle size distributions were obtained by varying the relative viscosities between rubbery phase and PP matrix. Transmission electron microscopy and computer‐aided image analysis were used to provide particle size information. In general, PP blends with smaller rubber particles are tougher and more ductile than those with larger particles, probably because the former represents a more efficient use of rubbery phase in promoting crazing and/or shear yielding. Samples with average particle diameter D̄ ≥ 0.5 μm were found to exhibit pronounced crazing. Within a given sample, no crazes appeared to develop around individual rubber particles with D < 0.5 μm. The higher the D, the greater the propensity to form crazes. The behavior of samples with D̄ ≪ 0.5 μm appeared to be dominated by shear yielding; very few crazes could be found. That there exists a critical rubber particle size is explained by the requirement that sufficient stress concentration be maintained to a finite radial distance to permit the initiation and growth of a craze, which requires a finite volume. Small particles, inducing smaller stress‐enhanced zones, are therefore not effective in initiating crazes.
Synthesis and rheological study of some maleic acid polyamides
Authors: Jaćović Mihailo S. , Djonlagić Jasna , Macknight William J. , Lenz Robert W.
Published: December 2004

The contributions of the cis and trans configurations of the main chain double bonds to the transition temperatures and rheological properties were determined for four well‐defined polymaleamides, which were prepared by the room temperature ring‐opening, step‐growth polymerization reactions of N,N′‐bisisomaleimide monomers with bifunctional primary diamines. The polymaleamides were glassy solids, which could be thermally isomerized into related polyfumaramides. The glass transition temperatures of the polyfumaramides, as determined by mechanical spectrometry, are systematically and markedly higher than those of the polymaleamides from which they were derived.
Recent studies on interpenetrating polymer networks
Authors: Frisch K. C. , Klempner D. , Xiao H. X. , Cassidy E. , Frisch H. L.
Published: December 2004

Recent investigations on interpenetrating polymer networks (IPNs) have included two component IPNs from polyurethanes and poly(methacrylates) and two component IPNs from polyurethanes and epoxies. All the IPNs were prepared by the simultaneous polymerization technique (SIN‐IPNs). Two types of IPNs, polyurethane‐poly(methyl methacrylate) (PU/PMMA) and polyurethane‐poly(methyl methacrylate‐methacrylic acid) (PU/PMMA‐MAA) were prepared. Improved phase miscibility and decreasing extent of phase separation was observed in both types of IPNs with increasing the NCO/OH ratio, decreasing molecular weight of the polyol in the PU and introduction of charge groups. A comparison was made between full‐IPNs, pseudo‐IPNs, graft copolymers and related homopolymers from polyurethanes and epoxies. Increased compatibility in full‐IPNs and graft copolymers was observed by means of DSC, SEM and was also further substantiated by a shift toward single Tgs as determined by dynamic mechanical spectroscopy. The introduction of opposite charge groups in two‐component IPNs from polyurethanes and epoxies led to improved compatibility (no phase separation) and enhanced mechanical properties.
A mathematical model for computer simulation of a direct continuous esterification process between terephthalic acid and ethylene glycol: Part 1. Model development
Authors: Yamada Toshiro , Imamura Yoshio , Makimura Osamu
Published: December 2004

A new mathematical model has been developed for the continuous esterification process of terephthalic acid (TPA) and ethlene glycol (EG) with consideration of oligomer characteristics. The liquid weight fraction in the reaction mixture, β, has been selected as a principal parameter in this model. The solubility of TPA in EG and bis β‐hydroxyethyl terephthalate (BHET) has been measured in order to estimate more precisely the concentration of each component. Good agreement has been obtained by plotting the log of solubility data of TPA in EG and BHET against the reciprocal of the absolute temperature with correlation coefficients of 0.998 and 0.989, respectively. The validity of these data has been verified in comparison with other data.
Phase diagrams and membranes
Authors: Lonsdale Harold K.
Published: December 2004

Over the past two decades, membrane technology has found application in a variety of industries, ranging from water desalination to gas separations. These new applications have come about because of the availability of high‐performance, permselective membranes. A key element in the development of these new membranes has been the discovery of “skinned” or asymmetric membranes. These membranes typically have an effective thickness on the order of 0.1 to 0.2 μm. They are essentially composite structures, consisting of a dense skin supported by a finely porous substrate. We now recognize that an understanding of the mechanism of formation of these asym‐metric membranes is available through binary and ternary phase diagrams. Membranes for microfiltration, ultrafiltration, reverse osmosis, and gas separations are now routinely produced by some form of “phase inversion” process, amenable to explanation through phase diagram considerations.
Structure formation during spinning of poly(p‐phenylenebenzobisthiazole) fiber
Authors: Cohen Y. , Thomas E. L.
Published: December 2004

The structure formed in the coagulation stage of the spinning process of poly(p‐phenylene benzobisthiazole) fiber is studied by electron microscopy. An oriented network of microfibrils with typical fibril diameters of about 80‐100Å is observed. We suggest that these microfibrils are the fundamental structural elements of the fiber. Thus, knowledge of the mechanism by which this initial structure is formed may allow for better control of final fiber properties. The relation of structure formation during coagulation to the phase diagram of a rigid polymer solution and to the kinetic mechanism of the phase transition is discussed.
Mechanical and thermal properties of an alternating methyl methacrylate styrene copolymer
Authors: Bataille P. , Granger F.
Published: December 2004

The copolymer resulting from the polymerization of methyl methacrylate and styrene in the aqueous phase was tested for its mechanical and thermal properties. The usual procedure to obtain such a copolymer is by radical polymerization, but it can be done also by an ionic solution polymerization and in most cases the copolymer obtained has a statistical polymer arrangement. As this polymer is made by a complex mechanism in the presence of zinc chloride and water, it has many interesting features. The polymerization itself in the presence of water has a good industrial appeal as it simplifies considerably the operations as well as eliminates the suspension phase solvent cost. Another feature is the molecular weight distribution; we have two definite nearly monodisperse groups of polymers—one of these groups has an average molecular weight of 107. The thermal properties of the polymers were studied as functions of the polymerization conditions and a mathematical expression was derived relating these factors. The mechanical properties of this, polymer compares favorably to available industrial products.
Bisbenzocyclobutene: A thermoset matrix host for rigid‐rod molecular composites
Authors: Chuah H. H. , Tan L.‐S. , Arnold F. E.
Published: December 2004

An approach to realize the reinforcement of a thermoset system at the molecular level by rigid‐rod polymers was investigated. A mixture of bisbenzocyclobutene (BCB)‐terminated imide oligomers constitutes the thermosetting component, and the rigid‐rod polymer utilized in the present study was poly(p‐phenylene benzothiazole) (PBT). The cure chemistry of the thermoset materials is based on the ability of benzocyclobutene functions to homopolymerize under the influence of heat. Thermal properties as well as film processing and mechanical properties of PBT/BCB thermoset composites are presented.
Development of an ionomer tracer for extruder residence time distribution experiments
Authors: Weiss R. A. , Stamato H.
Published: December 2004

A polymeric tracer was developed from the tributylamine salt of lightly sulfonated polystyrene. The residence time distribution (RTD) measured for the extrusion of polystyrene with this tracer was compared with that measured using conventional particulate tracers, In general, the particulate tracers had a longer mean residence time and a broader RTD, which were attributed to increased mixing of the particulates.
Viscosity modeling during epoxy resin cure
Authors: Schmitt George , Wiley John , Gotro Jeffrey
Published: December 2004

A model is presented that describes the changing melt viscosity of an epoxy laminating resin during its cure. The model incorporates chemical as well as physical factors. The predictions of the model are compared to experimental data using resin cured at several rates of heat‐rise, and at a fixed heat‐rise profile using resin preadvanced to different extents of reaction. Agreement is good, particularly at rapid heat‐rise rates, typical of those used in production.
Analytical melting model for polymer pellets
Authors: Kuo S. H. , Chung C. I.
Published: December 2004

The plasticating or melting behavior of polymer pellets sliding on a hot metal surface was investigated. An analytical model was developed for predicting the melting rate and the shear stress of an incompletely compacted solid bed of pellets in terms of the rheological and thermodynamic properties of the polymer, the pellet size, the degree of compaction, and the operating conditions. This investigation extends the results of the previous investigators obtained for a fully compacted solid bed of polymers to an incompletely compacted solid bed of polymers, closely representing the initial stage of the plasticating mechanism inside a screw extruder. Experimental verification of the analytical model developed here was made by testing six different commercial polymers.
Kinetic studies of the crystallization of nylon‐6 block copolymers
Authors: Limtasiri T. , Grossman S. J. , Huang J. C.
Published: December 2004

The crystallization kinetics of nylon‐6 and nylon‐6 block copolymers (NBC's) containing 1–3 mole % poly(ethylene oxide), PEO, were measured under isothermal and linear cooling conditions. The Avrami equation was used to fit the data. The range of the Avrami index n was from 1.5 to 2.2 for the system studied in the temperature range from 400–454 K. Maximum rate of crystallization was observed in the above temperature range. Nylon‐6 block copolymers showed the maximum crystallization rate at a lower temperature than nylon‐6. When the soft segment exceeded 3 mole %, no crystallization was observed. Cooling rate studies showed the same tendency. The crystallization rate behavior of nylon‐6 block copolymers was similar to the pure nylon.
Phase behavior of blends of poly(vinyl chloride) with an α‐methyl styrene/acrylonitrile copolymer
Authors: Kim J. H. , Barlow J. W. , Paul D. R.
Published: December 2004

Poly(vinyl chloride), PVC, is shown to be miscible with an α‐methyl styrene/acrylonitrile copolymer, αMSAN, containing 30 percent AN by weight using differential scanning calorimetry for blends prepared by several methods. Melt blending gave single Tg mixtures; whereas, solution techniques gave results that depended on the solvent choice and the manner in which it was removed. These blends do not phase separate on heating prior to significant PVC decomposition (∼250°C) in contrast to PVC/SAN blends which have much lower cloud points. Repulsion between α‐methyl styrene and acrylonitrile units in the copolymer is the principal cause for miscibility of this system as shown by an analysis based on a binary interaction model using calorimetry data for low molecular weight liquid analog compounds.
A study of the miscibility of blends of polybutadiene and styrene‐butadiene copolymers
Authors: Shah Ketan , White James L. , Min Kyonsuku
Published: December 2004

We investigated the miscibility of polybutadienes with butadiene‐styrene copolymers of varying styrene content. The methods of optical microscopy, differential scanning calorimetry, and small angle light scattering (SALS) were used. All polymers/copolymers used in this study have equivalent butadiene microstructures. Copolymers with high styrene levels are immiscible with polybutadiene. The tendency to miscibility increases with decreasing styrene content. An upper critical solution temperature is observed with the 23 percent styrene copolymer.
Investigations of the layered structure of injection‐molded polypropylene discs and of its behavior in tensile tests. Dedicated to Prof. H. Janeschitz‐Kriegl on the occasion of his 65th birthday
Authors: Fleischmann E. , Zipper P. , Jánosi A. , Geymayer W. , Koppelmann J. , Schurz J.
Published: December 2004

The tensile test behavior of specimens taken from polypropylene discs injection‐molded with and without packing, respectively, was studied. The initial state of the different layers of the specimens and their stressed state, respectively, are characterized by small‐angle X‐ray scattering (SAXS), wide‐angle X‐ray scattering (WAXS), measurements of birefringence and of mechanical properties, and by light‐microscopic investigations. The results off these experiments altogether give a detailed representation of the behavior of the different layers of the specimens in the tensile test.
A novel positive resist for deep UV lithography
Authors: Yamaoka Tsuguo , Nishiki Masashi , Koseki Ken'Ichi , Koshiba Mitsunobu
Published: December 2004

A novel positive resist was prepared by sensitizing poly(p‐trimethylsilyloxystyrene) with p‐nitro‐benzyl‐9, 10‐diethoxyanthracene‐2‐sulfonate (NBAS) which was found to be a deep UV bleachable acid precursor. The silylated polymer is converted to alkaline soluble poly(p‐hydroxy‐styrene) in the presence of acid and a small amount of water. The photoresist gives high resolution positive patterns on imagewise exposure with deep UV light with a sensitivity of 15 mJ/cm2.
A model for the thermal and chemorheological behavior of thermosets. I: Processing of epoxy‐based composites
Authors: Kenny J. M. , Apicella A. , Nicolais L.
Published: December 2004

The rheological and thermokinetic aspects of the cure of epoxy based composite laminates are analyzed by means of a computer program developed using the heat transfer and heat generating characteristics of a polymerizable system. In particular, the temperature and degree of cure influence on the resin viscosity have been first considered, then the temperature profiles, calculated according to an appropriate kinetic and heat transfer modeling, have been used to predict the corresponding viscosity profiles. Molecular and thermocalorimetric parameters are used for the prediction of the theoretical chemorheological behavior. Commercial epoxy systems commonly used in the preparation of carbon fiber laminates have been characterized by Differential Scanning Calorimetry (DSC) and dynamic viscosity measurements and the results are compared with the theoretically predicted values.
Monitoring the cure processing properties of unsaturated polyesters in situ during fabrication
Authors: Kranbuehl D. E. , Averty P. H. , Hoff M. , Hoffman R. D.
Published: December 2004

The use of frequency dependent impedance measurements in the Hz to MHz range for continuous in situ measurements of the processing properties of unsaturated polyester resins both in a laboratory and manufacturing tool is presented. The frequency dependence of the complex impedance is used to separate and measure ionic and dipolar mobility. These two parameters are used as molecular probes to monitor in‐situ the reaction onset, point of maximum flow, gel, post gel buildup in modulus, and the final degree of hardness.
Process control for polypropylene degradation during reactive extrusion
Authors: Pabedinskas A. , Cluett W. R. , Balke S. T.
Published: December 2004

This paper describes the development of process control schemes for the free radical initiated (reactive) degradation of polypropylene in an extruder (reactive extrusion). The objective of the work was to control the amount of degradation in order to produce polypropylene with a specified molecular weight. The die pressure drop was used as a measure of the amount of degradation (the measured variable) and the initiator concentration was used to control the amount of degradation (the manipulated variable). The reactive degradation process was modeled empirically to determine the dynamic relationship between the input degradation initiator concentration and the output die pressure drop. Several control schemes were evaluated for controlling the die pressure drop (amount of degradation) with emphasis placed on schemes designed to overcome the non‐linear process gain and dead time.
Hydrodynamic analysis of a banbury mixer 2‐D flow simulations for the entire mixing chamber
Authors: Cheng Jing‐Jy , Manas‐Zloczower Ica
Published: December 2004

Banbury mixers are widely used in polymer processing. The mechanics of flow in the chamber of an internal mixer are complex and difficult to analyze due to the complicated geometry and the highly transient character of the flow. For this work, a fluid dynamics analysis package—FIDAP, using the finite element method, was implemented to simulate the flow patterns for a Banbury B mixer. A 2‐D flow analysis was carried out for the whole mixing chamber with two counter‐rotating rotors. A power‐law model fluid was used to characterize the rheological behavior of the mixture. 18 different geometries were selected to represent the relative position of the two rotors during their revolution. Streamlines and pressure contours were plotted for each geometry. Transient pressure profiles at fixed locations in the chamber wall were compared with experimental data. The comparison shows good agreement between theoretical predictions and experimental observations.
Fracture toughness and crack growth mechanism for multiphase polymers
Authors: Zhang M‐J. , Zhi F‐X. , Su X‐R.
Published: December 2004

The fracture behavior of acrylonitrile‐butadiene‐styrene (ABS) was investigated using the J‐integral method under monotonic loading. Two ways were used to monitor the onset of crack growth: the dyeing method and the length of craze region ahead of initial notch. The blunting at the crack tip and crack growth mechanism for ABS Was observed using a scanning electron microscope. Before the onset of crack growth, the energy put into material was dissipated to create crazes ahead of the initial notch and to deform the material at the crack tip. A part of the energy was released to create a new crack surface after the onset, of crack growth.
Crystallization kinetics of oriented polymers
Authors: Gupta R. K. , Auyeung K. F.
Published: December 2004

The increase in the rate of polymer crystallization brought about by mechanical deformation above the polymer glass‐transition temperature is examined. For flexible macromolecules, this deformation results in alignment and extension of polymer chains. By hypothesizing that the instantaneous growth rate at a given constant temperature depends uniquely on the polymer chain orientation in the surrounding melt, an explicit expression is obtained for the growth rate of a spherulite in terms of experimentally measurable quantities. Isothermal meltspinning experiments were conducted with poly(ethylene terephthalate) (PET) using a laboratory setup. Very large values of the total crystallinity and significantly enhanced values of the crystallization rate were generated by operating at different temperatures that straddle the temperature of maximum crystallization rate for the quiescent melt. Measured rates of crystallization do, indeed, correlate with the instantaneous amorphous orientation. Furthermore, a masterplot, independent of temperature, is obtained by normalizing the crystallization rate under spinning conditions with that under quiescent conditions. This is the first time that such data have become available, and, given the processing history, such a master plot should be of use in predicting the crystallinity levels in actual nonisothermal industrial experiments.
Laser annealing of polyetheretherketone (PEEK)
Authors: Fang Shwu‐Jen , Salovey R. , Allen Susan D.
Published: December 2004

Changes in the crystalline morphology and thermal behavior of amorphous poly(etheretherketone) (PEEK) films have been effected by irradiation with a continuous wave CO2 laser. At high laser scan rate and power, PEEK films melt and requench into amorphous transparent films. At a scanning velocity of 14 μm/s and incident intensities ≥ 4.8 W/cm2 and a Gaussian beam radius of 1.63 mm, PEEK films crystallize “completely” above Tg on laser annealing. Irradiation of PEEK films on a quartz substrate reduces the cooling rate, allowing slower and more perfect recrystallization. Similar changes are effected by reducing the laser scan velocity or by increasing the laser power. Depending on the experimental conditions, laser induced recrystallization may occur on annealing above Tg or on cooling from the melt.
Crack initiation and propagation paths for brittle failures in aligned and misaligned pipe butt fusion joints
Authors: Parmar Ravindra , Bowman Jeremy
Published: December 2004

Medium density polyethylene pipes of 63, 90, and 125mm outside diameter, together with 63mm high density polyethylene pipes, were butt fusion joined to give aligned and controlled misaligned joints. These fabricated systems were tested at elevated temperatures under constant and fluctuating internal pressure loading. For brittle failures at the butt fusion joint, a thorough examination has been made of the points of crack initiation and the crack propagation path in relation to weld microstructure, It has been observed that the butt fusion process induces the presence of a long sharp notch formed when the internal weld bead rolls towards the pipe. This notch initiates circumferential joint failures, particularly in misaligned butt joints. Points of disturbance on the inner weld bead appear capable of inducing axial cracks at the butt fusion joint but only for aligned joints. The microstructure at the butt fusion joint was seen to have little influence on the crack propagation path.
Cold compaction of polyether‐etherketone and nickel powder blends
Authors: Reilly J. J. , Kamel I. L.
Published: December 2004

This study deals with the cold compaction of polyether‐etherketone (PEEK) and nickel powder blends. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were utilized for this investigation. These PEEK powders included fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P). Each of the four different PEEK powders were blended with about 10 vol−% nickel powder (Novamet) using a dry mixing technique. These PEEK/nickel powder blends were then successfully compacted at room temperature. Green strengths as high as 39.5 MPa and 26.3 MPa were measured on nickel filled 150 grade and 450 grade compacts, respectively. The higher strength values of the nickel filled compacts compared to their respective unfilled ones were attributed to a higher degree of mechanical interlocking and plastic deformation, which was induced in the polymer particles during compaction by the hard nickel filler. These composites also exhibited lower viscoelastic recoveries than their respective unfilled compacts. Electrical resistivities as low as 0.06 ohm‐cm were achieved by compacting 150P/nickel powder blends. This resistivity value agreed well with the calculated value predicted from the literature.