bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of reaction injection molding process of polyurethane‐unsaturated polyester blends. Part II: Mechanical properties
Authors: Kim J. H. , Kim S. C. 
Published: December 2004

AbstractThe mechanical properties of polyurethane‐unsaturated polyester interpenetrating polymer networks (IPNs) that were prepared by reaction injection molding (RIM) process were measured with variations In composition, cross‐link density, and relative reaction rate. From dynamic mechanical analysis (DMA), it was found that the two component polymers had a good compatibility over the whole composition range. The tensile strengths of the blends were greater than those of the pure components and had a maximum value at 50/50 composition. The modulus of elasticity and surface hardness decreased and the impact strength increased as the polyurethane content was increased, but the changes were not high at low polyurethane content, below 50%. For higher cross‐link density, the compatibility was enhanced and the mechanical properties were improved. When the reaction rates of the components were different, some extent of phase separation was found in DMA and the properties were affected adversely.
Concentration, temperature and deformation effects in concentrated polymer solutions with volatile solvents
Authors: Foster R. W. , Lindt J. T. 
Published: December 2004

AbstractA novel high pressure polymer solution viscometer has been experimentally evaluated using the polystyrene/ethylbenzene system. The polymer solutions range in concentration from 60 weight percent polystyrene to the pure melt. The overall temperature range is 132°C to 240°C. The shear rates range from roughly 5 s−1 to 2000 s−1. It has been concluded that the present method is useful in determining the shear dependent behavior of these volatile solutions, The shear dependent nature of this system is consistent with accepted non‐Newtonian viscosity theory.
Structure‐property relationships for thermoplastic block terpolymers containing poly(styrene‐p‐tert‐butylstyrene) copolymer end segments
Authors: Chen John C. , Fetters Lewis J. 
Published: December 2004

AbstractTerpolymers containing polybutadiene as a central segment and diblock or random copolymer terminal units of equimolar amounts of styrene and p‐tert‐butylstyrene have been synthesized and evaluated. The structure property relationships were examined by a combination of transmission electron microscopy (morphology), dynamic viscoelasticity measurements, and melt rheological evaluations. The presence of p‐tert‐butylstyrene was found to lead, under certain circumstances, to thermoplastic elastomers exhibiting good phase separation and mechanical properties at ambient temperature along with Newtonian melt viscosities at low shear rates at elevated temperatures. This latter behavior is in contrast with that exhibited by conventional poly(styrene‐diene‐styrene) triblock copolymers.
Cure kinetics of an epoxide/anhydride/amine resin system: A fractional‐life method approach
Authors: Lee Sung‐Nung , Yuo Wu‐Bin 
Published: December 2004

AbstractA fractional‐life method coupled with dynamic differential scanning calorimetry (DSC) scan was employed to study the kinetics of the isothermal polymerization of the DGEBA (diglycidyl ether bisphenol A)/HHPA (hexahydrophthalic anhydride)/BDMA (benzyl dimethyl amine) resin system. This method avoids the problem of uncertainty in the total heat evolution in the isothermal DSC scan, The reaction orders obtained for this epoxy resin vary from 1.05 to 1.44 in the temperature range 118–135°C and are believed to be more accurate than those determined in previous studies.
An approach for estimating the permeation of phosphonofluoridates into a high polymer matrix part 1. Development of the approach
Authors: Mangaraj D. , Pfau J. P. , Luttinger M. , Block F. , Magee W. S. 
Published: December 2004

AbstractAn approach has been developed to estimate the solubility and diffusivity of toxic phosphonofluoridates in high molecular weight polymeric matrices based upon experimentation with nontoxic simulants. This approach is based on Gee's relation for estimating solubility (equilibrium swelling) from knowledge of the solubility parameters for the polymer and the simulant liquids concerned and on Van Krevelen's relation between diffusivity and activation energy of diffusion. The latter is interpolated from a standard plot of activation energy of diffusion against penetrant molar volume. Equilibrium swelling values and diffusivities for toxic alkyl phosphonofluoridates in styrene‐butadiene rubber (SBR) and low density polyethylene (LDPE) were estimated from results of swelling measurements (as a function of time and at three different temperatures) involving the two polymers and a series of nontoxic liquids, similar to the toxic alkyl phosphonofluoridates.
Nonisothermal flow of a generalized power‐law fluid in converging sections for rubber extrusion
Authors: Kakouris A. P. , Freakley P. K. , Harrison M. C. 
Published: December 2004

AbstractA method for predicting pressure drop and temperature distribution in convergent sections is proposed. The generalized power‐law rheological equation of state is used. Only the shear component of the converging flow is considered in order to estimate its contribution to total flow in such sections. A finite‐difference scheme was used to simulate the flow. The method was applied to an ethylenepropylene terpolymer compound using different angles of approach for which the pressure drop and the extrudate temperature had been measured experimentally. Comparison with theoretically predicted data showed excellent agreement for small angles, while for large angles the inclusion of extensional effects was found to be necessary. The contribution of viscous dissipation effects was found to be negligible for the converging sections tested.
Catalyst fragmentation during propylene polymerization: Part I. The effects of grain size and structure
Authors: Ferrero Monica A. , Chiovetta Mario G. 
Published: December 2004

AbstractFragmentation of support/catalyst particles during propylene polymerization in the gas phase is analyzed via a mathematical model including energy and mass transfer with chemical reaction processes. The rupture phenomenon is considered specifically by the model, and evaluated as it proceeds in time, Two different regions are recognized in the polymerizing particle at fragmentation time: an inner core resembling the original solid support/catalyst structure, and an external set of layers where most of the polymerization occurs. Model predictions concerning the effects of fragmentation on polymerization are discussed. The influence of different degrees of fragmentation on thermal runaways and monomer availability at active sites located inside the support/catalyst/polymer complex is shown. Monomer concentration profiles inside the growing particles are explained in terms of the combined fragmentation‐polymerization interaction. Results show a strong influence of catalyst structure on critical phenomena during early polymerization stages, and suggest the possibility of controlling critical parameters via the definition of fragment structure at catalyst preparation time.
Blends of polycarbonate and poly(hexamethylene sebacate): II. Effect of molecular weight on compatibility
Authors: Shih K. S. , Beatty C. L. 
Published: December 2004

AbstractBlends of polycarbonate (PC) and poly(hexamethylene sebacate) (HMS) with two different molecular weights were prepared and their thermal properties were studied via differential scanning calorimetry. It was found that the high molecular weight PC (HPC) and high molecular weight HMS (HHMS) were partially miscible as evidenced by the decrease in glass transition temperature of HPC in the blends. This partial miscibility is attributed to the interaction of the carbonyl dipole of the ester group and the highly polarizable aromatic carbonate structure. When the low molecular weight PC or HMS was used, the compatibility was enhanced because of the increased entropic contribution to the Gibbs free energy of mixing. In all the blends prepared, the PC crystallized as a result of the plasticizing effect of HMS. Bisphenol‐A diphenyl carbonate (dimer) was synthesized and used as the dimeric model of PC. This material was found to be an excellent diluent for HPC. A single glass transition was found in the HPC/dimer system and the temperature was dependent on the composition. The Couchman's equation was found to fit very well the glass transition temperature versus composition relationship for this system. A single glass transition was also found in the HHMS/dimer system. The melting point depression analysis was performed and resulted in a very low heat of fusion for the 100% crystalline HHMS. It may suggest that the dimer and HHMS are not completely miscible in the amorphous region.
Structure‐property relationships in polyamide/acrylonitrile‐butadiene‐styrene (ABS) blends
Authors: Howe David V. , Wolkowicz Michael D. 
Published: December 2004

AbstractThe structures and physical properties of four blends of poly(acrylonitrile‐co‐styrene‐g‐butadiene) (ABS) materials with polycaprolactam (PA6) have been characterized. The blends were separated into components by selective solvent extraction and were found to contain different structures: Blend A contained no PA6 grafts. Blend B contained PA6 grafted onto both soluble and insoluble ABS. Blend C contained PA6 grafted onto soluble poly(styrene‐co‐acrylonitrile) (p‐SAN). In Blend D, PA6 was grafted onto both the insoluble ABS and the p‐SAN phases. Transmission electron microscopy showed different morphologies in the blends. Blend A had a co‐continuous, somewhat laminar structure, while Blend D consisted of an ABS phase dispersed in a PA6 continuum. Blends B and C had intermediate structures. All four blends, however, had very similar rheological and physical properties despite the variation in structure.
The effect of viscosity ratio on the morphology of polypropylene/polycarbonate blends during processing
Authors: Favis B. D. , Chalifoux J. P. 
Published: December 2004

AbstractThe size of the minor phase in an immiscible polymer blend can have a significant effect on properties such as the impact strength. Few studies, however, have quantitatively considered the parameters controlling the size of the dispersed phase. In this paper, light and scanning electron microscopy have been used to examine the size of the minor phase in polypropylene/polycarbonate blends after melt processing. The size was examined as a function of both the viscosity ratio (p) and the torque ratio (TR). The viscosity ratio is studied in the regions of p > 1 and p < 1. p has a marked effect on the morphology of the dispersed phase with the phase size increasing by a factor of 3 to 4 times from p = 4.5 to p = 17.3. Reduction in the size of the minor phase was achieved below p = 1 with the minimum particle size occurring at p ≃ 0.15. The results for these systems indicate the presence of upper and lower limits of p beyond which deformation becomes difficult. This is shown to be similar in some respects to the behavior of Newtonian fluids in shear flow, although the upper limit extends beyond that observed in the Newtonian fluid studies.
Phase behavior studies of the system polystyrene‐polybutadiene‐chloroform. II. Modification of the Flory‐Huggins theory
Authors: Tseng H.‐S. , Lloyd D. R. , Ward T. C. 
Published: December 2004

AbstractPhase behavior of polymer‐polymer‐solvent systems can be determined using gel permeation chromatography. This technique enables one to generate the binodal curve and tie lines relating coexisting phases, to locate the critical point and, through the use of an appropriate solution theory, to calculate interaction parameters. Previous studies of the incompatible polystyrene‐polybutadiene‐chloroform system indicated that the classical Flory‐Huggins theory yields an anomalous behavior of negative interaction parameters. Probable causes are specific interactions due to the polar nature of chloroform plus failure to account for the concentration dependence of the polystyrene‐chloroform interaction. A modified version of the Flory‐Huggins theory incorporating concentration dependence of polymer‐solvent interaction was used to reevaluate the polystyrene‐polybutadiene‐chloroform system. This approach yields positive interaction parameters for the incompatible system polystyrene and polybutadiene.
Reaction‐induced crystallization kinetics during the anionic polymerization of ϵ‐caprolactam
Authors: Lee Kwang Hee , Kim Sung Chul 
Published: December 2004

AbstractThe kinetics of crystallization during anioiiic polymerization of ϵ‐caprolactam was studied by the adiabatic temperature rise method, A new kinetic model for the non‐isothermal crystallization was derived and the possibility of its application was Investigated. By evaluating the parameters in the model for the given adiabatic system, the crystallization behavior during the; polymerization process was analyzed. The experimental and calculated temperature rise showed a very good agreement, which indicated that the model equation was appropriate to describe the non‐isothermal reaction‐induced crystallization kinetics in this study. The melting temperature of the reaction mixture increased steadily due to the change of the crystal structure with conversion. The equilibrium crystallinity was higher when the crystallization started in the presence of unreacted monomer than when the crystallization occurred after polymerization was completed. At lower conversion, the reaction mixture was less viscous, a condition that made transport to the liquid‐crystal interlace easier, and thus the activation energy for transport decreased. On the other hand, the increasing mobility resulted in difficulty in forming stable nuclei arid the free energy of nucleation increased.
Relationship between electron sensitivity and chemical structures of polymers as electron beam (EB) resists. V: Polyamides containing sulfur groups as positive eb resists
Authors: Oguchi Kiyoshi , Ygneyama Sachiko , Sanul Kohei , Ogata Naoya , Takahashi Yoichi , Nakada Tomihiro 
Published: December 2004

AbstractPolyamidethioethers were synthesized and evaluated as positive electron beam (EB) resists, The polyamidethioethers decomposed easily with EB exposure. At high doses (indicating low sensitivity), crosslinking reactions occurred for polyamidethioethers having C‐S bonds produced by Michael addition, but the other polyamidethioethers did not crosslink. The C‐S bonds produced by Michael addition may influence crosslinking rather than decomposition. The sensitivity of oxidized polyamidethioether was higher than that of the nonoxidized polymer with no change in resolution. The oxidized polyamidethioether had a high sensitivity and a high resolution, and is adaptable as a positive EB resist.
Computation of the gel effect in multifunctional self‐polymerization in the presence of intramolecular reactions
Authors: Kumar A, , Khandelwal P. K. 
Published: December 2004

AbstractIntramolecular reactions in the step‐growth polymerization of multifunctional monomer, RAf, were modeled. The rate constant for this step was taken from the Monte Carlo studies of Plate and Noah. Species Pvn, with v Intramolecular bonds and chain length n, was defined, and differential equations governing their molecular weight distribution (MWD) in hatch reactors were written. An algorithm of computation valid up to the gel point was developed, and the process of gelation was studied under the variation of the rate constant parameters of the intramolecular reaction step. It was found that the larger the molecule, the greater is its tendency to form intramolecular bonds. We devised a mathematical method to find the conversion of A groups on Pon species. Whenever this reaches a critical value {= l/(f−1)}, conditions for gelation are generated and molecules of infinite structure begin to form. In the presence of intramolecular reactions, the tendency to form a network is reduced because larger molecules undergo cyclization and there is consequently a shift in the gel point, which has been computed in this work.
Latent skin in asymmetric loeb‐type hollow fiber membrane
Authors: Castellari Carlo , Francesconi Romolo , Ottani Stefano , Comelli Fabio , Pezzin Giovanni 
Published: December 2004

AbstractA computer simulation model for the latent skin growth inside a hollow fiber polymeric membrane Is developed. The evaporation step is studied using a solvent evaporation Law and a concentration‐dependent diffusion coefficient, both derived from data. The solvent concentration profiles inside the fiber are obtained as a function of the evaporation time for different sets of the parameters governing the internal diffusion and the surface evaporation of the solvent. The computer model enables estimation of the role of the parameters in the growth of the asymmetric latent skin.
Rheological properties of thermotropic liquid crystalline aromatic copolyesters
Authors: Zhou Zhenglong , Wu Xiuge , Wang Meirong 
Published: December 2004

AbstractA series of thermotropic liquid crystalline polyesters based on p‐acetoxybenzoic acid, naphthalene dicarboxylic acid, hydroquinone diacetate, and poly(ethylene terephthalate) were prepared via melt polycondensation. The anisotropic melts were studied by means of thermal optical testing, differential scanning calorimetry, scanning electron microscopy. X‐ray diffraction, and rheological methods. It was found that the copolyesters in the mesomorphic state exhibit drastic shear‐thinning and the experimental results indicate that the non‐Newtonian Indexnis in the range of 0.17 to 0.50, the flow‐activation energies ΔEηare 297.1 to 182.0 KJ/mol over the shear rate of 10 to 1000 S−1at temperature 225 to 270°C; and the mesomorphic copolymers are readily oriented during processing, resulting in highly oriented as‐spun fibers.
Influence of the processing conditions on morphology and deformation behavior of poly(butylene terephthalate) (PBT)
Authors: Ludwig H.‐J. , Eyerer P. 
Published: December 2004

AbstractThis paper discusses the effect of varying cooling rates during crystallization on the spherulitic structure of poly(butalene terephthalate). Light microscopy, transmission electron microscopy, and differential scanning calorimetry were used to examine specimens. The mechanical properties of the polymers studied were examined by a variety of methods.
The effect of processing conditions on the microstructure of embossed polyethylene films
Authors: Kamal M. R. , Haber A. , Li Song 
Published: December 2004

AbstractFilm embossing is a mechanical process in which a flat film is transformed into an embossed product. During the process, thermal and stress fields are applied Lo the polymer, causing changes in the microstructure and physical dimensions of the material. The engineering analysis of the process requires the study of various aspects relating to the characterization of the microstructure before and after embossing, A variety of techniques were employed to characterize the properties and microstructure of the embossed film in relation to: crystallinity, orientation, mechanical properties, and dimensions of the embossed films. The thermal treatment of the polymer film was shown to be the most significant factor in the process. By controlling the thermal treatment of the film, it is possible to manipulate the properties and dimensions of the embossed film. The important aspects: influencing thermal treatment include the radiation heater temperature, preheat roll temperature, line velocity, and film thickness. The initial film orientation and embossing pressure have a minor effect on the final properties of the embossed film. The main effect of the embossing pressure is on the bulk thickness of the embossed film.
Production of controlled‐rheology polypropylene resins by peroxide promoted degradation during extrusion
Authors: Tzoganakis C. , Vlachopoulos J. , Hamielec A. E. 
Published: December 2004

AbstractResults of experimental and modeling studies of the peroxide promoted degradation of polypropylene (PP) are presented. Experiments were carried out, in glass ampoules and in a plasticating extruder. The initiator, 2.5‐dimethyl‐2,5‐bis(tert‐butylperoxy)hexane was used as a radical generator. The extruder used had a 38 mm diameter and 24:1 L/D single‐screw. In these experiments, the effect of peroxide concentration and screw speed on the molecular weight distribution (MWD) of the polypropylene resin was studied. Samples collected from the experimental runs were analyzed for melt flow index (MFI), flow curve, extrudate swell, and MWD. The measured data are presented and correlations among various parameters are considered. Generally, it can be concluded that controlled‐rheology (CR) resins with lower molecular weight, narrower MWD, and reduced viscosity and elasticity, can be produced, A kinetic model for the peroxide Initiated degradation of PP is proposed. Simulations based on this model are compared with experimental data for the production of CR resins. The experimental data were obtained from three sources: (i) industry, (ii) literature, and (iii) present experimental work. The comparison was done in terms of average molecular weights of the resin. Agreement between model predictions and experimental results is quite satisfactory suggesting that this model should find use in commercial practice.
Effects of mechanical drawing on the structure and properties of peek
Authors: Lee Lidia H. , Vanselow Janice J. , Schneider Nathaniel S. 
Published: December 2004

AbstractThis study examines the effects of crystallinity and temperature on the mechanical properties of PEEK. Crystallinity in PEEK Increases with annealing temperature up to a maximum of 28 percent with a melting point at 335°C. A minor melting peak also occurs about 10°C above the annealing temperature. In cold drawing the samples exhibited a yield stress and necking followed by homogeneous drawing. The yield stress increases with crystallinity, but there is no change in the modulus. The extension in the necking process also increases with crystallinity, however there is only a slight increase in extension‐to‐break since necking is compensated by the final amount of homogeneous drawing. The yield stress of PEEK when drawn at Tg (145°C) is significantly lower than at room temperature indicating a reduction in mechanical properties at temperatures approaching Tg. After mechanical drawing the minor melting peak disappears and on heating the material undergoes cold crystallization near the onset of Tg. There is evidence that this minor crystalline component might contribute to the yield stress changes with annealing history. Cold drawing induces crystallization of amorphous PEEK but decreases crystallinity and generates microscopic voids in crystalline PEEK, The various effects of crystallinity on mechanical properties could be important in determining the stress response of PEEK as the matrix in composites.
Concurrent enthalpy recovery and curing phenomena in epoxy encapsulating materials for semiconductor applications
Authors: Belton Daniel J. , Molter Michael 
Published: December 2004

AbstractPost mold thermal processing of epoxy encapsulated semiconductor devices is accomplished in order to optimize the properties of the encapsulating material. Traditionally, such processes were believed to alter solely the state of cure in such systems. We have examined the effects of aging at temperatures close to, but below the molding temperature via dynamic mechanical spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry as a function of molding temperature. The large property changes observed during aging for samples molded at the lowest temperatures studied were attributed to physical aging phenomena in the presence of low levels of chemical reaction. As the molding temperature was increased chemical aging, phenomena began to precede the volume recovery associated with physical aging, and the overall property shift was altered. It is the intent of this paper to examine in detail the microstructural basis for such observations, as well as the time dependence of the overall property shifts.