bluuebunny/crossref_metadata_2025_split huggingface dataset:
The compatibility of linear low density polyethylene‐polypropylene blends: Viscosity ratio plots
Authors: Bains M. , Balke S. T. , Reck D. , Horn J. 
Published: May 2005

AbstractBlends of linear low density polyethylene (LLDPE) and polypropylene (PP) show diverse mechanical property behavior in the published literature. The main objectives of this work were: to investigate the effect of viscosity of the component phases on the mechanical properties of such blends and to use the results to obtain a method for compatibilizing diaper manufacturing waste. The significant result of the study was that although LLDPE/PP blends are often termed “incompatible,” when viscosity of the components was more closely matched to each other, increases of as much as 50% in tensile strength and modulus were observed over the “rule of mixtures” line. Also, scanning electron microscopy then showed a more diffuse interface between the component phases. Three dimensional views of plots of viscosity ratio of the blend components as a function of temperature and shear rate were used to demonstrate the closer matching of viscosities for the blend components of the higher performing blends. In processing diaper manufacturing waste, addition of a high molecular weight PP in a manufacturing scale single screw extruder, to provide a closer match of viscosities of the blend components, significantly improved mechanical properties.
Zone drawn NEW‐TPI thermoplastic polyimide and its blends with Xydar liquid crystalline polymer
Authors: Aihara Yoshihiko , Cebe Peggy 
Published: May 2005

AbstractIn this work we report the effects of single stage zone drawing on the properties of NEW‐TPI thermoplastic polyimide homopolymer, and its blends with Amoco's Xydar liquid crystalline polymer. Zone drawing was performed first on homopolymer NEW‐TPI films to determine the effect of load weight, heater speed, and drawing temperature on the attainable draw ratio. Degree of crystallinity and chain orientation increase as the draw ratio increases for NEW‐TPI. Blends of NEW‐TPI/Xydar compositions 90/10 and 70/30 were studied next. In blends, the Xydar component is not molecularly dispersed, and is initially preferentially oriented along the machine direction during the film processing stage. Xydar acts as a nucleation site and lowers the temperature for crystallization of the NEW‐TPI from the rubbery amorphous state. Zone drawing was performed either parallel or perpendicular to Xydar's initial preferred orientation direction. Blends with lower Xydar fraction could be zone‐drawn to higher ratios. Zone drawing perpendicular to Xydar's initial orientation direction also resulted in increased draw ratio. Dynamic mechanical properties of the zone drawn materials were studied. In homopolymer NEW‐TPI, dynamic modulus increased by a factor of two to 4.0 GPa in zone drawn films, largely as a result of the formation of oriented crystallites. In the blends, the modulus parallel to Xydar's initial orientation direction was greater than that in the transverse direction. Depending upon composition and test direction, zone drawing increased the dynamic moduli of the blends from 1.5 up to 2.7 times, in the temperature range from 150°C to 300°C.
Processing/morphology correlations in poly(benzoate‐co‐naphthoate) liquid crystalline polymers
Authors: Hudson Steven D. , Lovinger Andrew J. , Venkataraman Sundar K. , Liu Chester , Manzione Louis T. 
Published: May 2005

AbstractThe molecular orientation and disclination defects in injection molded bulk samples of liquid crystal polymers have been revealed by transmission electron microscopy (TEM). Using a recently optimized lamellar decoration and etch technique for use with poly(benzoate‐co‐naphthoate), we have studied in detail the skin‐core morphology produced by realistic injection molding processing. In the skin, the director is observed to be highly aligned along the flow direction, and the defect density is very low (10 cm−2). In the core, however, the defect density is six orders of magnitude greater, and the director lies predominantly in the plane defined by the flow and neutral directions. The flow during processing is turbulent, giving rise to distinct morphological features and disclination clusters. When the material is filled at 20% volume fraction with long glass fibers, the molecular and filler orientations are nearly parallel. Dimensional precision also correlates with the morphology and improves with increasing core fraction.
Degradation of unstabilized medium‐density polyethylene pipes in hot‐water applications
Authors: Viebke J. , Elble E. , Ifwarson M. , Gedde U. W. 
Published: May 2005

AbstractPipes of an unstabilized medium‐density polyethylene have been pressure tested with internal stagnant water and moderately circulating air as the external medium at temperatures ranging from 70 to 105°C and changes in molecular structure and crystallinity have been studied. The stage III (fracture induced by thermal oxidation) life of the unstabilized polyethylene pipes was less than 12% of the life of the corresponding stabilized polyethylene pipes. Infrared spectroscopy and size exclusion chromatography showed an earlier and more extensive increase in the quantities of oxidation end‐products and a more pronounced decrease in molar mass of the outer‐wall‐material than of the inner‐wall‐material of the pipe. Mass crystallinity, measured by differential scanning calorimetry, increased on an average by a quantity corresponding to 45 methylene groups per chain scission event. The life of the unstabilized pipe was divided into an induction period during which no detectable thermal oxidation occurred and a subsequent polymer degradation period. The induction period exhibited an Arrhenius‐temperature‐dependence with an activation energy of 75 kJ mol−1.
Three‐dimensional modeling of reaction injection molding. I
Authors: Lo Yu‐Wen , Reible Danny D. , Collier John R. , Chen Cheng‐Ho 
Published: May 2005

AbstractIn this research a model to simulate both the filling the curing stages of a reaction injection molding (RIM) process in complex three‐dimensional molds is developed. This model can be used to predict not only the temperature and conversion changes with time but also the front position during filling. Using given physical and chemical properties of the RIM system, moldability can be determined in advance. The numerical techniques used in this research include adaptation of the SIMPLE algorithm developed by Patankar for a moving‐front, two‐phase system with non‐negligible inertial effects, and exothermic chemical reaction. The model predictions of temperature and conversion compare favorably with available data on simple two‐dimensional molds. The ability of the model to predict the dynamics of filling in more complicated molds was verified by comparison to mold filling experiments with water and a polyurethane foam.
Investigation of processing‐structure‐properties relationships in polyethylene blown films
Authors: Patel Rajen M. , Butler Thomas I. , Walton Kim L. , Knight G. W. 
Published: May 2005

AbstractMolecular orientation imparted during film fabrication is known to have a major effect on mechanical and thermal properties of both glassy and semicrystalline polymers. A three‐variable Box‐Behnken designed experiment was used to study the effects of die gap, die land length, and blowup ratio (BUR) on key linear low density polyethylene (LLDPE) blown film properties at constant final film thickness. In addition, differences in molecular orientation in the films were studied using optical birefringence and shrinkage methods. Measured key film properties were correlated to processing conditions and to measured molecular orientation. Die land length had no significant effect on film structure and properties. All LLDPE films exhibited about 70 to 80% shrinkage in the machine direction (MD) but expanded in the cross direction (CD). Most films exhibited negative in‐plane birefringence. MD Elmendorf tear was found to be inversely related to drawdown ratio and MD shrinkage, suggesting that MD tear is dependent primarily on amorphous chain extension and hence, amorphous segments orientation for LLDPE blown films. Dart impact strength of the films was shown to be related to MD shrinkage and to the induced surface roughness due to varying die gap. In a separate study, blown films of three high pressure LDPEs were fabricated under nearly identical conditions. No correlation was found between birefringence and shrinkage data on the LDPE blown films.
On the pressure dependency of the viscosity of molten polymers
Authors: Kadijk S. E. , Van Den Brule B. H. A. A. 
Published: May 2005

AbstractA slit viscometer to measure the viscosity of polymer melts under processing conditions is described. Along the slit a pressure drop is generated by applying a pressure at both the entrance and the exit. In this way the pressure in the center can be controlled independently of the shear rate. The pressure gradient in the slit is measured by means of three pressure transducers which are mounted in the region of fully developed flow. Results of pressure‐dependent viscosity measurements on polystyrene, polyacrylonitrile‐butadiene‐styrene, and polypropylene are presented in a shear rate range of five decades. The flow curves obtained at different pressures and temperatures can be shifted onto a master curve. The shear thinning behavior of the three materials is adequately described with the generalized Cross‐Carreau equation, while the zero shear viscosity is modeled with a generalized Arrhenius‐W.L.F. relationship, incorporating a pressure dependency. Alternatively, it is possible to describe the zero shear viscosity in terms of the free volume fraction and the temperature.
Laser welding of polymers
Authors: Nonhof C. J. 
Published: May 2005

AbstractDeep penetration welding and cutting of metals can be carried out at high speed with relatively low laser power. The efficient coupling of the laser radiation to the metal is due to the formation of a “keyhole.” Over the years, an attempt has been made to transfer the results on metals to plastics. It will be shown here that keyhole welding of plastics is limited to the very restricted set of plastics that have a boiling point. Volume heating, a mechanism that is not applicable to metals, is restricted to plastics with a good transparency for the incident radiation and with a high optical quality. Finally, surface heating is shown to be the most common mechanism for heating plastics.
Enhancement of electrical conductivity of uniaxially and biaxially processed poly(p‐phenylene sulfide) films
Authors: Ko Dong‐Hwi , Min Kyonsuku 
Published: May 2005

AbstractA fundamental study of electrical conductivity of uniaxially and biaxially stretched poly‐p‐phenylene sulfide (PPS) film was conducted. In this paper, we paid special attention to understand the effect of processing conditions on the electrical conductivity as well as the conduction mechanism of tantalum pentafluoride (TaF5) doped PPS. The electrical conductivity of PPS film was measured by a four‐point probe method in the parallel and perpendicular directions to the stretching direction. The infrared spectra of doped and undoped stretched PPS films demonstrate that the TaF5 doping causes distortion (polaron) in PPS chain and conduction. A similar discussion was reported by Tsukamoto, et al. (1, 2). They found the delocalization of π‐electrons in doped PPS by X‐ray spectoscopy (XPS), infrared spectroscopy (IR), and C13‐NMR. The conductivity of doped PPS films increased with increasing stretching ratio. The crystallinity effect on the electrical conductivity was investigated by changing crystallinity of PPS films in terms of annealing and multi‐axially stretching. Orientation development was investigated by wide angle X‐ray scattering and birefringence techniques. The relationship between conductivity and orientation of stretched PPS films was investigated by introducing electrical anisotropy.
Kinetic studies and process analysis of the reactive compatibilization of nylon 6/polypropylene blends
Authors: Dagli S. S. , Xanthos M. , Biesenberger J. A. 
Published: May 2005

AbstractThis article describes a study on the reactive compatibilization of nylon 6 (N6) and polypropylene (PP) blends through a functionalized PP. A graft copolymer was formed in‐situ by reacting an acid modified PP with N6 during blend compounding. The compatibilization reactions are studied in detail. Kinetics were estimated by means of experiments in a batch mixer. Three time constants were estimated, corresponding to (a) reactions, (b) melting of polymers, and (c) melt mixing. The effects of temperature and rotor speed on the reaction kinetics were also measured. There was a substantial increase in initial reaction rate, as the rotor speed was increased. Increasing the temperature did not significantly affect the reaction rate. Process parameters important for such a reactive compatibilization process were identified by statistically designed experiments in a co‐roatating intermeshing twin‐screw extruder. Screw speed, presence of venting, and sequence of feeding were shown to have a noticeable effect on the reactive compatibilization process during continuous compounding.
High modulus polypropylene: Effect of polymer and processing variables on morphology and properties
Authors: Phillips R. , Herbert G. , News J. , Wolkowicz M. 
Published: May 2005

AbstractThe morphology and properties of high modulus polypropylenes (PP) are characterized over a wide range of material variables. These variables include the tacticity, room temperature xylene solubles (XSRT), molecular weight, melt flow rate (MFR), and polydispersity index (PI). Flexural modulus in quench‐cooled compression moldings of propylene homopolymer can be correlated to the volume fraction crystallinity, ϕc, by an empirical logarithmic dependence. The quantitative zero orientation results for the quench‐cooled compression moldings provide an approximate crystallinity normalization for oriented moldings. WAXS analyses of crystalline orientation were determined over a range of melt temperatures and mold locations and correlated to the skin area fraction by optical microscopy. WAXS analysis of the balance of orientations for the crystallographic axes suggest that the orientation balance is primarily determined by the “melt orientability” of the resin type. An empirical description of flexural modulus in injection molded PP is developed for the range of material variables and molding conditions studied. This description is represented as a function of crystallinity‐normalized modulus vs. the frozen‐in crystalline orientation.
Reactive extrusion of acrylic acid grafted polypropylene with hexadecylamine
Authors: Wang X. C. , Tzoganakis C. , Rempel G. L. 
Published: May 2005

AbstractTo study the possibility of the production of branched polypropylene (PP) by a reactive extrusion (REX) route, side chains were introduced on the backbone of a polypropylene material by reacting hexadecylamine with acrylic acid grafted PP. Experiments were carried out both in solution and in the melt, and the products were analyzed by FTIR, elemental analysis, dynamic mechanical, and rheological techniques. Analysis of the FTIR spectra of the samples produced in the solution reactions, at an equal molar ratio of [ –NH2]/[–COOH] without catalyst addition and without removal of the by‐product, revealed that the formation of imide was increased with increasing the reaction time up to 10 h, while a further increase in reaction time resulted in a reversal of the reaction. In the REX experiments, FTIR analysis showed that the imide formation increased with the [–NH2]/[–COOH] molar ratio. At a molar ratio of one, more imide was present in the REX product than the in‐solution one. Elemental analysis suggested that the nitrogen content in the products initially increased with [–NH2]/[–COOH] molar ratio and then reached an almost constant value at molar ratio values of about unity. The glass transition temperature (Tg) was measured by dynamic mechanical analysis (DMA), and it was found that the attachment of the alkyl chains caused a reduction in Tg of the products. Finally, rheological measurements showed that the shear viscosity of the products increased with the amine/carboxyl molar ratio at low shear rates and that their moduli were enhanced as a result of the attachment of the alkyl side chains.
Interfacial tension in polymer melts. Part II: Effects of temperature and molecular weight on interfacial tension
Authors: Kamal M. R. , Lai‐Fook R. , Demarquette N. R. 
Published: May 2005

AbstractInterfacial tension is one of the most important parameters that govern the morphology of polymer blends and the quality of adhesion between polymers. However, few data are available on interfacial tension due to experimental difficulties. A pendant drop apparatus was used for the determination of the interfacial tension for the polymer pair polypropylene/polystyrene (PP/PS). The effects of temperature and molecular weight were evaluated. The range of temperatures used was from 178° to 250°C, and the range of molecular weights used was from 1590 to 400,000. The interfacial tension decreased linearly with increasing temperature. With only one exception, higher molecular weight systems showed weaker dependence of interfacial tension on temperature than lower molecular weight systems. Also, polydisperse systems showed a stronger dependency on temperature than the monodisperse systems. The value of the interfacial tension, which increases with molecular weight, appears to level off at molecular weights above the entanglement chain length. For the polymer pair PP/PS, the dependency of the interfacial tension on the number average molecular weight appears to follow the well‐known semi‐empirical (−2/3) power rule over most of the range of molecular weights. Comparable correlations were obtained with values of the power between −1/2 and −1.0.
Numerical simulation of the fountain flow problem for viscoelastic fluids
Authors: Sato Toru , Richardson Stephen M. 
Published: May 2005

AbstractFountain flow for isothermal viscoelastic fluids is simulated by a numerical method based on a combination of a finite element method and a finite volume method. For the treatment of moving free surfaces, a fringe element generation method is used. Circulating flow and elongation in the transverse direction at the melt front are simulated well. Numerical results also suggest that circulation in fountain flow and viscoelastic retardation may give rise to symmetric V‐shaped patterns of birefringence between the center‐plane and wall. Such information on molecular orientation in fountain flow is important for physical properties of thick molded products.
Thermal studies of blends of poly(phenylene sulfide) (PPS) with poly(phenylene sulfide sulfone) (PPSS) and with poly(phenylene sulfide ether) (PPSE)
Authors: Brostow Witold , Seo Kwan‐Ho , Beak Jong B. , Lim Jeong C. , Seo Kwan‐Ho 
Published: May 2005

AbstractThe miscibilities of poly(phenylene) sulfide/poly(phenylene sulfide sulfone) (PPS/PPSS) and poly(phenylene) sulfide/poly(phenylene sulfide ether) (PPS/PPSE) blends were invesigated in terms of shifts of glass transition temperatures Tg of pure PPS, PPSS, a dn PPSE. The crystallization kinetics of PPS/PPSS blends was also studied as a function of molar composition. The PPS/PPSS and PPS/PPSE blends are respectively partially and fully miscible. PPSE shows a plasticizing effect on PPS as does PPS on PPSS, which necessarily improves te processibility in the respective systems. We can control Tg and melting temperature Tm of PPS by varying amounts of PPSE in blends. The melt crystallization temperature Tmc of PPS/PPSE blends was higher than that of the PPSE homopolymer. Therefore, these blends require shorter cycle times in processing than pure PPSE.The overall rate of crystallization for PPS/PPSS blends follows the Avrami equation with an exponent ≃2. The maximal rate of crystallization for PPS/PPSS blends occurs at a temperatre higher by 10°C than that for PPS, while the crystallization half time t1/2 is 4 times shorter. In the cold crystallization range, crystal growth rates increase and Avrami exponents decrease significantly as the temperature increases.
Reinforcement of mechanical properties of a poly(ethylene terephthalate) and polycarbonate blend by the addition of thermotropic liquid crystalline polymer
Authors: Kwon Soon Kil , Chung In Jae 
Published: May 2005

AbstractMechanical properties of the ternary blends of poly(ethylene terephthalate) (PET), polycarbonate (PC), and thermotropic liquid crystalline (TCLP, Vectra A950) were investigated. The ternary blends were prepared by varying the amount TLCP but fixing the ration of PET and PC. The fiber fallen freely through the capillary die had the highest initial modulus (1.46 GPa)/tensile strength (73 MPa) when 10% of TLCP was added. Above this TLCP content, however initial modulus and tensile strength decreased. The scanning electron microscope (SEM) micrographs of the TLCP phase which was extracted by dissolving PET/PC matrix from the blend showed the fine fibrils formed at 5 and 10% of TLCP, while the aggregated TLCP phases at 20 and 30% of TLCP. It was suggested that the decrease of the mechanical properties of the resulting blend was caused by the aggregation of TLCP phase above 10% of TLCP. A high draw ratio gave a rise to the formation of highly oriented fibrils of TLCP phase in the PET/PC matrix and the improvement of mechanical properties of the ternary blend.
Aging characteristics of oriented ply(ethylene terephthalate)
Authors: Mukherjee Sumit , Jabarin Saleh A. 
Published: May 2005

AbstractThe physical aging characteristics of oriented poly(ethylene terephthalate) (PET), have been studied ad functions of storage time and temperature below the glass transition temperature (Tg) of PET. The free volume relaxation, associated with aging, has been characterized by the enthalpy at Tg, as measured by differential scanning calorimetry. The effects of the free volume relaxation on mechanical properties and the mode of failure have been investigated. It has been determined that a correlation exists between the enthalpy of relaxation and the ductile‐to‐brittle failure transition. Molecular orientation reduces significantly the enthalpy of relaxation, resulting in the disappearance of the ductile‐to‐brittle transition when highly oriented samples are aged over time. It has been established that a minimum amount of orientation is required to reduce or eliminate the effects of PET aging. Molecular orientation has also been found to reduce craze formation when oriented PET is exposed to a stress‐cracking medium at constant stress.
Esterification in reactive extrusion
Authors: Maier C. , Lambla M. 
Published: May 2005

AbstractA condensation type reaction has been studied for reactive extrusion in a twin‐screw extruder. The esterification reaction is to graft a nonylphenyl‐ethoxylate (NP8) onto a pre‐maleated ethylene‐propylene (EPRMA). The kinetics were initially characterized in the static mixture using a thermally controlled call in a FTIR spectrometer. These were then used to predict the conversion along the length of the extruder screws, having determined the residence time distribution at various sampling locations. A reasonable fit with the data was obtained, although the kinetics seem to be slightly faster in the flowing medium than those predicted. Over short screw distances, the equilibrium rapidly approached equilibrium. Moreover, the NP8 was shown to penetrate the EPRMA within screw distance of less than 1.3 L/D, despite using conveying elements known for their minimal mixing capacity. Within the molten medium, a mixing model showed that obtaining the expected conversion in a product does not imply that the reactants in the product have in fact been well mixed.