bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase diagrams and membranes
Authors: Lonsdale Harold K. 
Published: December 2004

AbstractOver 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

AbstractThe 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

AbstractThe 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

AbstractAn 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractPoly(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

AbstractWe 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractThis 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

AbstractBanbury 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

AbstractThe 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

AbstractThe 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

AbstractChanges 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

AbstractMedium 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

AbstractThis 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.
Sol‐Gel transition and crystallization kinetics of ultra‐high molecular weight polyethylene/decalin solution
Authors: Jo Won Ho , Kwon Ick Hwan , Seoul Chang 
Published: December 2004

AbstractThe gel melting temperature and crystallization kinetics of ultra‐high molecular weight polyethylene (UHMW‐PE)/decalin systems were investigated. Two methods were used to determine gel melting temperature; thermomechanical analysis (TMA) with a penetration probe and differential scanning calorimetry (DSC). The melting points determined from TMA and DSC were in good agreement, indicating that the crystallization of UHME‐PE is an essential step for gelation. The gel melting temperature increases with UHMW‐PE concentration. The change in gel melting temperature with composition results from interaction of the components in the amorphous phase. The gelation and crystallization rates increase with decreasing UHMW‐PE concentration.
Physical aging in poly(methyl methacrylate)poly(styrene‐co‐acrylonitrile) blends. Part II: Enthalpy relaxation
Authors: Mijović J. , Ho T. , Kwei T. K. 
Published: December 2004

AbstractAn investigation of the effect of physical aging on excess enthalpy of compatible polymer blends was carried out. Poly(methyl methacrylate) (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were chosen for this study. Blends of different ratios of PMMA and SAN were physically aged at different times and temperatures below their glass transition (Tg) and then subjected to enthalpy relaxation measurement in a differential scanning calorimeter (DSC). An improved procedure was developed and, employed to analyze the data. The error associated with the calculation of the normalized deviation in enthalpy, known as the “Φ” function, was below 4%. The relaxation was observed to proceed faster at higher aging temperature. It was also found that at higher aging temperatures of Tg – 20 and Tg– 35°C, enthalpy relaxation in SAN‐rich blends proceeds faster than in PMMA rich blends, while at the low aging temperature of Tg– 50°C the rate of relaxation becomes independent of the composition.
Ultrasonic welding of thermoplastics in the far‐field
Authors: Benatar Avraham , Cheng Zhang 
Published: December 2004

AbstractIn far‐field ultrasonic welding of plastic parts the distance between the ultrasonic horn and the joint is greater than 6 mm. This study investigated the farfield ultrasonic welding of amorphous (acrylo butadiene styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. Far‐field welding worked well for amorphous polymers. Weld strength improved substantially with increasing amplitude of vibration at the joint interface. Increasing the weld pressure and/or the weld time also resulted in higher weld strengths. Far‐field ultrasonic welding was not successful for semicrystalline polymers. The parts melted and deformed at the horn/part interface with little or no melting at the joint interface. A model for wave propagation in viscoelastic materials, which was developed to predict the vibration amplitude experienced at the joint interface, indicates that increasing the length of the samples to a half a wavelength should improve the far‐field welding of semicrystalline polymers by maximizing the amplitude of vibration at the joint interface.
Ultrasonic welding of PEEK graphite APC‐2 composites
Authors: Benatar Avraham , Gutowski Timothy G. 
Published: December 2004

AbstractThe ultrasonic welding process is modeled using a five part model that includes mechanics and vibration of the parts, viscoelastic heating, heat transfer, flow and wetting, and intermolecular diffusion. The model predicts that melting and flow occur in steps, which has been confirmed by experiments. The model also indicates the possibility of monitoring joint quality by measuring the dynamic mechanical impedance of the parts during welding, which has also been verified experimentally by indirectly monitoring the magnitude of the impedance. via measurements of both the power and the acceleration of the base. When the melt fronts of the energy directors meet, at the end of welding, the dynamic impedance of the composites' interface is shown to rise rapidly. This raises the possibility of developing closed loop control procedures for the ultrasonic welding of thermoplastic composites. Ultrasonic welding of polyetheretherketone (PEEK) graphite APC‐2 composites produced joints with excellent strengths.