bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal conductivity of plastic foams
Authors: Williams R. J. J. , Aldao C. M. 
Published: December 2004

AbstractA simple equation enabling the prediction of the thermal conductivity of plastic foams, without the aid of adjustable parameters, is proposed. The equation is based on a recurrent method, previously developed, that showed reasonable agreement with experimental results. Ways of decreasing the thermal radiation contribution are shown. In particular, the influence of cell size, radiation transmission through solid membranes, and low‐emissivity boundary surfaces are analyzed. Errors involved in steady techniques of measuring the thermal conductivity associated with radiation are discussed.
Design of two‐stage extractor screws
Authors: Squires P. H. 
Published: December 2004

AbstractA basis for design of two‐stage extractor screws is developed with special focus on determining optimum design of the final pumping section in order to maximize pressure‐generating capability. Departure from the conventional square‐pitch helix angle of 17.7° appears justified in this section of the screw where pressure‐development capability is critical to successful performance. Optimization can produce gains of 5 to 30 percent in pressure (or in corresponding length reductions), the exact benefits depending on the non‐Newtonian behavior of the melt and on the optimization strategy selected.
Process control of injection molding
Authors: Sanschagrin Bernard 
Published: December 2004

AbstractThis paper discusses the most important input parameters affecting the conventional injection‐molding process and describes a closed‐loop control system for determining the interaction between ten process inputs and three output parameters. The input parameters are: back pressure, holding pressure, injection time, open mold time, shot size, clamping pressure, injection pressure, screw speed, and boost cut‐off. The output parameters studied are: part weight, maximum cavity pressure, and maximum mold deflection.
Moldability studies in reactive polymer processing
Authors: Manzione L. T. , Osinski J. S. 
Published: December 2004

AbstractReactive polymer processing is the combined polymerization and processing of reactive prepolymers in a single operation. It encompasses a wide variety of processing methods including Reaction Injection Molding (RIM), a relatively new and growing fabrication method. Reaction Injection Molding utilizes impingement mixing of low viscosity fluids, injection of the reactive mixture into a mold, and polymerization therein to enable the molding of large plastic items. Polyurethane is currently the most commercially utilized RIM material although a number of other systems such as epoxy, nylon, and polyester are also suitable. Non‐urethane systems such as epoxy are often not as amenable to the process, however, since they are slower reactions and have a potentially damaging exotherm. A comprehensive analysis was developed to determine if a molding system is processable by RIM. Criteria for processability were established and include the ability to mix on impingement, fill large molds characteristic of the process, and provide a short cycle time without promoting a damaging exotherm. The treatment, consisting of both experimental and numerical techniques, was applied to identify potential epoxy molding systems, establish their processing window, and conduct an optimization of the process parameters to evaluate productivity. The analysis and its conclusions are applicable to most reactive polymer processing operations that employ a rapid, exothermic, polymerization reaction.
Determination of time independent component of the complex modulus during cure of thermosetting systems
Authors: Farris Richard J. , Lee Charles 
Published: December 2004

AbstractA recent development suggests an approach to measure the equilibrium modulus through an impulse method. This paper is to report an attempt to apply such methods in measuring the changes of the equilibrium modulus of a thermosetting system during isothermal cures. Dynamic modulus changes were also measured and the results were correlated with that from the impulse method. At two different temperatures of cure, the equilibrium modulus values measured were very similar when the dynamic measurements showed tan δ = 1. At this point, it is not certain if the measured modulus is the real time independent portion of the elastic modulus, or contains the long relaxation time constant portion of the relaxation spectrum which appears to be pseudo‐time independent at the time scale and the instrumental sensitivity of the present experimental set‐up. This paper demonstrates the ease with which the impulse technique can be applied and suggests possible limitations or refinements.
Head to head polymers. XXV: Properties of head to head polyisobutylene
Authors: Malanga Michael , Vogl Otto 
Published: December 2004

AbstractHead‐to‐head polyisobutylene, prepared by the Grignard coupling reaction of 2,2,3,3‐tetramethyl‐1,4‐dibromobutane had molecular weight of 3,000 to 10,000 and was characterized by wide angle x‐ray diffraction, optical microscopy and thermal behavior. Head‐to‐head polyisobutylene is crystalline, with a crystalline melting point of 187°C and a glass transition temperature of 87°C (measured by DSC at a scan rate of 20°/min.); these values compare to a glass transition temperature of head‐to‐tail polyisobutylene of similar molecular weight of −61°C and a crystalline melting point of 5°C, which can only be observed when the sample was stretched. The maximum rate of degradation of head‐to‐head polyisobutylene (20°/min. programmed temperature increase) is at 315°C, 70°C lower than that of head‐to‐tail polyisobutylene.
A phenomenological master curve for viscosity—structure data for two phase polymer systems in simple shear flow
Authors: Lyngaae‐Jorgensen J. 
Published: December 2004

AbstractA master curve hypothesis is established based on a mass balance and an assumption of continuous stress through interfaces for well dispersed two phase systems with “defined” zero shear viscosity. The master curve, which is in reasonable accordance with experimental data is represented in a double logarithmic plot of log (ηT/T,0) against log \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{\eta _{T,0} M_C H\rho}}{{c^2 RT}}\dot \gamma _T} \right) $\end{document}. Mc is the molecular weight between entanglements, H = M̄w/M̄n, ρ is the density, c is the polymer concentration, all defined for the continuous phase. ηT and ηT,0 are the viscosity and zero shear viscosity of the blend, ηT is the apparent shear rate, R the gas constant, and T is absolute temperature.
A survey of dual phase continuity and miscibility in interpenetrating polymer networks, making use of selective decrosslinking and dissolution of one component: Poly(n‐butyl acrylate)/polystyrene
Authors: Sperling L. H. , Widmaier J. M. 
Published: December 2004

AbstractA sequential interpenetrating polymer network, IPN, may be defined as a combination of two polymers in network form, at least one of which was polymerized or crosslinked in the presence of the other. Two major problems of interest to sequential IPN's relate to phase continuity and extent of mixing within each phase. A first attempt to define the molar volume of a network is made in terms of the molar volume of the polymer between crosslinks. This permits a thermodynamic calculation of the changes in molecular mixing expected as a function of crosslink density. The experimental system was poly(n‐butyl acrylate)/polystyrene IPN's, where the PnBA was crosslinked with acrylic acid anhydride. This last may be selectively hydrolyzed, forming a semi‐IPN, and then the PnBA can be extracted. Scanning electron microscopy and dynamic mechanical spectroscopy were carried out at each stage.
Heating and bonding mechanisms in ultrasonic welding of thermoplastics
Authors: Tolunay M. N. , Dawson P. R. , Wang K. K. 
Published: December 2004

AbstractAn experimental study of the heating and bonding mechanisms in ultrasonic welding is described. Polystyrene specimens were joined under a variety of welding conditions while the temperatures at the interface and within the interior of these specimens were measured. The power input, amplitude of vibrations, and amount of deformation during welding were measured concurrently. In general, the rate of heating at the interface is greatest at the beginning of the weld cycle, but slows markedly after the interface temperature reaches approximately 250°C. The interface temperature peaks well before the weld is completed. Temperatures within the body increase most rapidly at temperatures near the glass transition temperature. Welded specimens were broken on a special testing apparatus under combined torsional and compressional loads to determine the weld strength. The results show that weld strength is dependent on the amount of energy input and the degree to which material flows out of the interface region. Possible mechanisms for heating and bonding during ultrasonic welding are discussed in light of the observed behavior.
Fiber fracture in reinforced thermoplastic processing
Authors: von Turkovich Richard , Erwin Lewis 
Published: December 2004

AbstractThe length reduction of reinforcing fibers in short‐fiber reinforced plastics during processing has been studied experimentally. It has been shown that fiber volume fraction, initial length, and initial state of dispersion have little effect on the final fiber length. In dilute suspension theory based on shearing flow conditions and fiber properties the flow stresses are found to be compatible with the experimental results and results which are found in the literature.
Poly (butyleneterephthalate)‐ethylenevinylacetate polymer blends
Authors: Pilati Francesco 
Published: December 2004

AbstractPolymerization of dimethylterephthalate (DMT) and 1,4‐butanediol (4G) carried out in the presence of about 15 weight percent of ethylene‐co‐vinylacetate copolymers (EVA), gave blends with average dimensions of the “soft domains” of a few microns. During polymerization, reaction between EVA and poly(butyleneterepthalate) (PBTP) takes place leading to the formation of macromolecules of PBTP‐g‐EVA and crosslinked EVA in addition to unreacted EVA and linear PBTP. These different chemical structures can be fractionated by selective solubility and quantitatively measured. Their relative amounts depend particularly on the percentage of vinylacetate (VA) in the initial EVA and on the time of reaction. During polymerization there is a retarding effect on the increasing of the molecular weight of linear PBTP which can be ascribed to the lower volatility of the acetate by‐products, derived from the reaction with EVA, which act as monofunctional impurities.
Solution processing and properties of molecular composite fibers and films
Authors: Hwang W‐F. , Wiff D. R. , Verschoore C. , Price G. E. , Helminiak T. E. , Adams W. W. 
Published: December 2004

AbstractExperimental studies of fiber wet‐spinning and solution processing of films of molecular composites are presented. The rigid rod polymer was poly (p‐phenylenebenzobisthiazole) (PPBT) and the flexible polymers were poly (2,5(6′)‐benzimidazole) (ABPBI) and poly (2,5(6′)‐benzothiazole) (ABPBT). Effects of the flexible polymer molecular entanglements in solution on the processing are discussed. These fibers and films have very high modulus and strength, which improve upon heat treatment. The uniaxial modulus of highly oriented molecular composites follows the linear rule of mixtures.
The preparation of oriented morphologies of the thermotropic aromatic copolyester of poly(ethylene terephthalate) and 80 mole percent p‐acetoxybenzoic acid
Authors: Zachariades Anagnostis E. , Logan John A. 
Published: December 2004

AbstractHighly oriented morphologies of poly(ethylene terephthalate) and 80 mole percent p‐acetoxybenzoic acid were prepared by shearing in an optical plate‐plate rheometer and by melt fiber drawing in a temperature range at which the copolyester was either in the semicrystalline state or liquid crystalline phase. The optical, thermal, and mechanical properties of the oriented films and drawn fibers depended significantly on the processing temperature.
The flow of a polymerizing liquid in a cylindrical pipe
Authors: Malkin A. Ya. , Sherysheva L. I. , Kulichikhin S. G. , Zhirkov P. V. 
Published: December 2004

AbstractThis work concerns the flow of a polymerizing liquid (a monomer) in a cylindrical pipe, which simulates the flow‐through reactor. A general formulation of the hydrodynamics of the rheokinetic problem in the non‐isothermal case of flow is given. The problem is solved with account taken of the existence of a radial distribution of velocity, residence time, and degree of conversion in the duct. The shape of the velocity profile undergoes change as the flow moves along the duct: it is originally parabolic (prior to reaction), then becomes strongly extended (at the intermediate stages of the reaction), and finally (upon completion of the reaction) assumes the parabolic shape again. It has been shown that in isothermal or nearly isothermal cases, it is possible to work out sufficiently simple scale‐up laws capable of establishing the dependence of the total degree of conversion and pressure drop on the time of polymerization and the geometric size of the reactor.
Recent advances in the theory of polymeric alloys
Authors: Noolandi Jaan 
Published: December 2004

AbstractThe theory of multicomponent polymeric systems, termed “polymeric alloys”, composed of block copolymers, homopolymers and solvents is discussed. We first review the microscopic interfacial properties of polymeric mixtures, highlighting the interfacial activity of block copolymers as emulsifying agents in incompatible homopolymer blends. We then turn to some interesting features of the phase diagrams, such as homopolymer‐induced mesophase formation and the existence of eutectic points, similar to those for metallurgical alloys. Finally, we address problems in polymer dynamics and present some recent new theoretical results based on the tube model.
Analysis of transient sorption and permeation of small molecules in multiphase polymer systems
Authors: Ottino J. M. , Shah N. 
Published: December 2004

AbstractThe transport of small molecules (gases) in incompatible polymer blends, semi‐crystalline polymers, and filled polymer systems is usually examined in terms of transient sorption and permeation experiments which yield effective values of diffusivity and permeability. From a modeling standpoint these complex systems can be regarded as composites with complex morphology whereas the gas can be considered as a molecular probe of the morphology and especially its connectedness. In this paper we present a brief review of transport descriptions in prototype ordered and disordered systems with special emphasis on simulation of transient measurements. The simulations presented are selected in such a way as to aid in the interpretation of experimental results obtained by sorption and permeation and in the construction and evaluation of morphologies with desired effective transport properties.
Thermal expansion of oriented glassy polymers
Authors: Smith K. J. 
Published: December 2004

AbstractA phenomenological model of entanglement networks is developed and applied to deformed glassy polymers. Thermal expansivities and birefringence are analyzed. The model assumes a stable network of entanglements up to draw ratios of about 5. Beyond that range the entanglement structure breaks down to maintain a nearly constant drawing stress. The results are used to determine the ultimate linear expansivities of atactic polystyrene.
Torsional braid analysis of bitumen‐liquid rubber mixtures
Authors: Kortschot M. , Woodhams R. T. 
Published: December 2004

AbstractThe performance of liquid rubbers as low‐temperature plastcizers for bitumen was evaluated by the torsional braid technique developed by Gillham. The low‐temperature dynamic mechanical properties of bitumen‐liquid rubber mixtures were measured from ambient to −100°C and compared with the corresponding fracture behavior using a modified Fraass test. Microscopic observation of the mixture revealed that the liquid rubber was partially soluble in the bitumen at 23°C and at concentrations greater than 10 percent tended to form colloidal dispersions of rubber particles having mean diameters of approximately 10 μm. The loss tangent maxima shifted to lower temperatures and became less pronounced as the concentration of liquid polybutadiene increased. The colloidal rubber dispersion further contributed to the ductility and reduced the brittle temperature of the bitumen at −30°C at 20 percent liquid rubber concentration. The reduction in the brittle temperature of the bitumen is related to the glass‐transition temperature of the added rubber, those rubbers having, the lowest glass‐transition temperatures being most efficient. Such modifications are necessary to reduce the tendency of asphaltic paving materials to crack in cold climates.
Positional small angle X‐ray scattering from flaws
Authors: LeGrand D. G. 
Published: December 2004

AbstractA simple theory of PSAXS (positional small angle X‐ray scattering) has been developed and used to aid in the interpretation of PSAXS data from flaws. The importance of the various experimental parameters has been studied and an explanation offered for apparent magnification. A comparison between images created by assumed flaw structures and from actual flaws has been made. It is proposed that three dimensional imaging of flaws can be performed.
Influence of composition, crystallization conditions and melt phase structure on solid morphology, kinetics of crystallization and thermal behavior of binary polymer/polymer blends
Authors: Martuscelli Ezio 
Published: December 2004

AbstractResults of an investigation on the morphology, the crystallization and the thermal behavior of several binary crystallizable blends are reported. The composition, molecular mass and crystallization conditions strongly influence the crystallization and the thermal behavior as well as the overall morphology of crystallizable binary blends. Quantities such as nucleation density (N), radial growth rate (G) of spherulites, overall rate of crystallization (K), and equilibrium melting temperature (Tm) are strongly dependent upon composition, crystallization conditions, and molecular mass of components. The type of dependence is to be related to the physical state of the melt, which, at the crystallization temperature, is in equilibrium with or coexists with the developing solid phase. In the ease of compatible blends such as poly(ethylene oxide)/poly(methyl methacrylate) the depression observed for G and Tm is mainly to be attributed to the diluent effect of the non‐crystallizable component. For such a blend it is found that, after crystallization, the non‐crystallizable component is trapped in intralamellar regions increasing the distance between adjacent lamellae. Depression of G, in the case of incompatible blends such as isotactic polypropylene/rubbers is mainly accounted for by rejection and deformation of rubber drops. The coexistence during crystallization of different processes such as molecular fractionation and segregation, preferential inclusion or dissolution of molecules with lower molecular mass and/or high degree of steric disorder of the crystallizable component in the phase rich in non‐crystallizable component and vice versa may explain some minima observed in the plots of T and Tm, vs. composition in the case of blends semicompatible in the melt. It was found that the addition of a second non‐crystallizable component causes drastic variations on some morphological and structural quantities of the semicrystalline matrix (isotactic polypropylene or nylon 6) such as the shape, dimensions, and regularity of spherulites and interspherulite boundary regions and lamella and interlamella thickness. In some cases the formation of new boundary lines connecting occluded particles are also observed. Such phenomena may have great importance on crack propagation and on impact behavior as well as on the tensile mechanical properties of binary blends characterized by a semicrystalline polymer component with a relatively high Tg and a rubber‐like component with a lower Tg.
Applications of polymer blends: Emphasis on recent advances
Authors: Robeson L. M. 
Published: December 2004

AbstractIn the past decade, polymer blend technology has achieved an important position in the field of polymer science. With increased academic and industrial research interest, the application of polymer blend technology to commercial utility has grown significantly. This review on the applications of polymer blends will cover the major commercial blends in the categories of styrene‐based polymer blends, poly(vinyl chloride) blends, polyacrylate blends, polyester and polycarbonate blends, polyolefin blends, elastomer blends, polyelectrolyte complexes, and interpenetrating polymer networks. New developments in polymer blend applications will be discussed in more detail. These systems include linear low‐density polyethylene blends with either low‐ or high‐density polyethylene, styrenemaleic anhydride terpolymer/ABS (acrylonitrile‐butadiene‐styrene) blends, polycarbonate/poly(butylene tetephthalate) blends, new PPO/polystyrene blends, and tetramethyl bisphenol A polycarbonate/impact polystyrene blends. Areas for future research to enhance the potential for polymer blend applications will be presented. The need for improved methods for predicting miscibility in polymer blends is discussed. Weldline strength is a major property deficiency of two‐phase systems (even those with mechanical compatibility), and future research effort appears warranted to resolve this deficiency. The use of polymeric compatibilization additives to polymer blends has shown promise as a method to improve mechanical compatibility in phase‐separated blends, and will be expected to be the subject of future research programs. Finally, the reuse of polymer scrap is discussed as a future application area for polymer blends. Unique applications recently proposed for polymer blends include immobilization of enzymes, permselective membranes, reverse osmosis membranes, selective ion‐exchange systems, and medical applications using polyelectrolyte complexes.
Preliminary results on toughening a linear‐low‐density polyethylene using thermoplastic elastomers
Authors: Baker W. E. , Catani A. M. 
Published: December 2004

AbstractThe effects of several commercially available thermoplastic elastomers (TPE) on a gas‐phase linear‐low‐density polyethylene (LLDPE) were studied using small‐scale commercial‐compounding techniques. The properties of blown films of these compositions were evaluated as a function of TPE type and composition and compared to unmodified LLDPE films. Ethylene/propylene elastomers had modest effects on the falling dart impact strength and machine‐direction tear propagation resistance while polyisobutylene and styrene block copolymers had more significant effects on these properties.
Laminar shear mixing in reaction injection molding
Authors: Bourne J. R. , Garcia‐Rosas J. 
Published: December 2004

AbstractTurbulent flow in the impingement mixing head of a reactions injection molding machine produces a laminated mixture, whose striations are mostly so thick that any subsequent copolymerization would be hindered by diffusion. However, further reduction in striation thickness occurs during laminar flow through the runner. This is calculated here and is a function of the radial position in the runner and of its length/diameter ratio. So, for example, when L/D = 10, it is predicted that at least 79 percent of, the reagent striations would be thin enough to permit reaction under kinetically controlled conditions.