bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer compatibility: Nylon‐epoxy resin blends
Authors: Wang Yung‐Yun , Chen Show‐An 
Published: December 2004

AbstractDynamic mechanical and differential scanning calorimetric studies of cured blends of alcohol soluble nylon with up to 40 percent epoxy resin indicate that the blends contain three phases: crystalline nylon phase, crosslinked nylon‐epoxy resin phase, and crosslinked epoxy resin phase. There are unreacted nylon chains distributed in the former two phases. The crystalline nylon phase is composed of partially reacted nylon chains and a small amount of unreacted nylon chains. Degree of ordering in this phase, both unreacted and partially reacted nylon chains, decreases with increasing epoxy resin content. Stress‐strain studies show that stress‐induced crystallization in partially reacted nylon chains in the crystalline nylon phase does occur during elongation resulting in the occurrence of a maximum tensile strength (at 5 percent epoxy resin content) as in the case of crosslinked rubber. Lap shear studies using the blend as an adhesive indicate a maximum strength at 30 percent epoxy resin content, implying that adhesion and crosslinking effects due to incorporation of epoxy resin play a major role in the adhesion performance.
Bulk density versus hydrostatic pressure characteristics of plastics in powder and pellet form
Authors: Smith N. M. , Parnaby J. 
Published: December 2004

AbstractIsothermal bulk density data measured for a number of commercially important plastics are presented for practical ranges of uniform hydrostatic pressure. Regression fitted polynomials are given for each plastic to facilitate the use of the data in computer‐aided lumped‐parameter, extrusion screw feed‐zone design methods. The cylindrical pressure‐test cell used for determining the data is described together with the theory governing its reliable operation.
Reactive rotational molding
Authors: Throne J. L. , Gianchandani J. 
Published: December 2004

AbstractIn order to identify the major fluid mechanical effects and catalog their domains of influence, an extensive study of flow behavior of reactive polyester resin systems in uniaxial, horizontal rotating systems has been undertaken. Four general flow phenomena are identified: cascading, where resin is withdrawn from the recirculating pool arid drains back; rimming, where resin is taken around the top of the cylinder by viscous forces; stable hydrocyst formation, where rings of fluid perpendicular to the axis of rotation are formed; and solid body rotation, where the resin on the mold wall is quite uniform and time‐independent. For most flow conditions, the desired region of solid body rotation apparently can be reached only by passing through each of the other flow regimes. Experimental work on polyester resin systems is compared with theoretical studies on flow stability, hydrocyst formation, and withdrawal from quiescent pools, and suitable correlations are developed. It is noted that the current correlations for stable hydrocyst formation are invalid for polyester resins and a simpler correlation is proposed.
The disk cure test—an evaluation method for flow and curing characteristics of thermosetting molding compounds
Authors: Tonogai Saburo , Hasegawa Kiichi , Fukuda Akinori 
Published: December 2004

AbstractA new and useful method, the Disk Cure Test, has been developed for evaluating the curing characteristics and moldability of thermosetting resins. The change of flowability during heating in a thin state at given temperatures is examined as a measure of curing rate. The optimum test conditions were established. The feature of this method was also clarified by comparing it with the conventional tests, such as Brabender plastometry, Curelastometry, and solvent‐extraction. Based on this information on curing, the moldability and the optimum molding conditions were established for various commercial and laboratory compositions, including phenolics, aminos, diallyl phthalates, epoxies, and poly(bismaleimide).
Use of “penalty” finite elements in analysis of polymer melt processing
Authors: Roylance David 
Published: December 2004

AbstractThe finite element method is an approximate numerical analysis approach of great applicability to a wide variety of field problems. This paper describes the formulation of a convenient method for treating fluid‐flow problems relevant to analysis of polymer processing operations, and illustrates its use by means of some linear and nonlinear problems in melt extrusion.
An integrated experimental study of the injection molding behavior of some polyethylene resins
Authors: Kamal Musa R. , Kalyon D. M. , Dealy J. M. 
Published: December 2004

AbstractThe present study reports on the results of an integrated experimental program to determine some of the important interactions between resin properties, moldability, and the microstructure and ultimate properties of molded articles. As part of the program, resins are characterized as to their rheological, thermal, and crystallization behavior. Then, the resins are injection molded in a laboratory machine employing simple, but highly instrumented molds in order to evaluate moldability and to produce moldings for testing and analysis. Microstructural analysis to determine morphology and orientation of the moldings is carried out utilizing polarized light microscopy and differential scanning calorimetry. Finally, shrinkage and tensile properties of the moldings are determined experimentally. To illustrate the utility of the proposed techniques, results are reported for two polyethylene resins' that exhibit superficially similar properties but, according to tests, show significant differences in moldability and product properties.
Shape changes during drawing of non‐circular extruded profiles
Authors: Griffith R. M. , Tsai J. T. 
Published: December 2004

AbstractDeformation during cooling and take‐up of rectangular, triangular and T‐shaped profiles were investigated. Experimental results show that there is an excellent agreement between changes in a cross‐section dimension and prediction from the theory for various take‐up speeds. The correlations decrease in the case where other process variables such as different melt temperatures and output rates are involved. Based on undrawn sample measurements, it has been concluded that to a high degree of approximation only a scaled‐down change in shape occurs along the drawing path after die swell is completed. Industrial practices in handling profiles during cooling and take‐up which may cause deviations from geometrically similar deformation were examined. Metal guides and local cooling by small water streams along the drawing path were used to impose shear forces on the profile. It was found that the effects of such shear forces has been small in comparison with the effects of elongational stress as indicated by only slight, if any, deviation from geometrically similar changes in cross‐sections. Based on the data obtained, it is concluded that feedback control during profile drawing to give correct size is feasible based on monitoring a single dimension. The correct shape can, however, be obtained only by choice of the proper die geometry and other extrusion conditions.
Hygrothermal history dependence of moisture sorption kinetics in epoxy resins
Authors: Apicella A. , Nicolais L. , Astarita G. , Drioli E. 
Published: December 2004

AbstractA history dependent solubility model is generalized in accordance with the Dual Mode Sorption Theory to take into account a history dependency of effective water diffusion coefficients in epoxy resins, based on hypothesized microcavitational damage due to the combined effects of temperature and sorbed moisture. Sorption data presented in a different paper are analyzed in the light of a transport model in which part of diffusing molecules are completely immobilized in the formed microcavities. The nature of the hypothesized damaging process is in agreement with the diffusion coefficient depressions and solubility increases experimentally found and theoretically predicted by the model.
Bending and breaking fibers in sheared suspensions
Authors: Salinas A. , Pittman J. F. T. 
Published: December 2004

AbstractAn experimental study was made of single fibers rotating and bending in Couette flow of a Newtonian liquid. A previous result for critical fiber buckling was re‐tested and found satisfactory, and the transition between ‘springy’ and ‘snake’ rotation was delineated. The minimum radius, of curvature achieved during rotation in the “snake orbit” regime was measured as a function of fiber aspect ratio, Young's modulus, and fluid shear stress. Two correlations are presented which are constrained to satisfy limiting conditions for very stiff and very flexible fibers. Together with a result from thin rod theory, these correlations may be used to predict breaking conditions for fibers of known Young's modulus and ultimate tensile strength. Predictions are tested in experiments where two types of glass fiber are broken in suspension and found satisfactory. Results show that several reinforcing materials will probably break within the range of conditions covered by our experiments, or in a region which can be treated by extrapolation from our results.
Thermoplastic interpenetrating polymer networks of a triblock copolymer elastomer and an lonomeric plastic. II. Mechanical behavior
Authors: Siegfried D. L. , Thomas D. A. , Sperling L. H. 
Published: December 2004

AbstractThermoplastic interpenetrating polymer networks, IPN's, are defined as combinations of two physically crosslinked polymers. A styrene‐b‐ethylene‐co‐butylene‐b‐styrene (SEBS) triblock elastomer was combined with an ionomer prepared from a random copolymer of styrene, methacrylic acid, and isoprene (90/10/1 by volume), and subsequently neutralized. Two subclasses of the thermoplastic IPN's were identified. A sequential polymerization method yielded the chemically blended thermoplastic IPN's (CBT IPN's). Melt blending of the separately synthesized polymers produced the mechanically blended thermoplastic IPN's (MBT IPN's). Stress‐strain and Rheovibron characterization revealed that the CBT IPN's exhibited greater tensile strength and higher elongation at break, but lower moduli than the MBT IPN materials of the same overall composition. Analysis of moduli data with the theories of Takayanagi, Davies, Budiansky, and Kerner disclosed more equal dual phase continuity for the MBT IPN's than the CBT IPN's at each composition. The low modulus of the more rubbery CBT IPN compositions was attributed to a decrease in the effective chain end‐to‐end distance between crosslinks in the elastomeric (EB) center block, brought about by the synthetic method.
The feasibility of electrical monitoring of resin cure with the charge‐flow transistor
Authors: Senturia Stephen D. , Sheppard Norman F. , Poh Soon Y. , Appelman Howard R. 
Published: December 2004

AbstractA new technique for the electrical monitoring of polymerization reactions such as resin cure is described. The technique is based on the charge‐flow transistor, which resembles a conventional metal‐oxide‐semiconductor field‐effect transistor (MOSFET), but with a portion of the metal gate replaced by the resin under study. Electrical signals obtained from several resins undergoing cure are presented, along with an electrical circuit model that can account for the principal features of these signals. The dramatic change in signal shape during cure can be related to corresponding changes in both the real and imaginary parts of the dielectric constant.
A biaxial extensiometer for molten plastics
Authors: Rhi‐Sausi J. , Dealy J. M. 
Published: December 2004

AbstractWhile biaxial stretching plays a central role in several polymer processes, there has been no technique suitable for laboratory study of controlled biaxial stretching of molten thermoplastics at typical melt processing temperatures. The sheet inflation technique, which has been used previously to study rubbers and very high viscosity melts, has been adapted for use with molten thermoplastics by the use of oil as an inflation medium. Problems encountered in the use of the first prototype were eliminated in a second model, which is thought to produce reliable results. Stress growth data are presented for a low density polyethylene and for a polystyrene. A basic limitation of the technique is that the maximum achievable strain is in the range of 1.3 to 1.7, and this is often insufficient to bring out the nonlinear viscoelastic behavior of the melt.
Mold release agents. I. Fatty acids and selected fluorinated compounds as releasants for polyurethane from cold rolled steel
Authors: Schneberger Gerald L. , Nakanishi Todd 
Published: December 2004

AbstractThe effect of saturated aliphatic fatty acids and a number of fluorinated polar organic compounds on the release of polyurethane foam from cold rolled steel has been investigated. Little release was observed with aliphatic acids of less than 10 carbons or with the organic compounds. Release behavior increased with aliphatic chain length from C12 to C18. Stearic acid release increased only marginally above 0.034 μ g/cm2. Infrared studies of demolded eluted surfaces indicated that stcaric acid at levels of up to 178 μ g/cm2 was apparently removed from the surface by foam.
Outgassing of high temperature‐resistant organic polymeric materials
Authors: Demaxss Peter 
Published: December 2004

AbstractFour polymeric materials, polyphenylene oxide, polyquinoline, acetylene substituted polyimide, and polybenzimidazole, reported to possess high‐temperature resistance, were investigated in order. to determine their outgassing characteristics as related to their suitability for high temperature applications in confined structures. The materials were sequentially exposed to 150, 250 and 450°C for 3 h periods and the types and amounts of their outgassed products were determined. The amounts of outgassed‐ products were small from polyquinoline, acetylene substituted polyimide, and polybenzimidazole. It was concluded that those materials would be suitable for use in applications where high‐temperature resistance (up to 450°C) is required, providing that normal ventilation is available. The quantity of outgassed products from polyphenylene oxide was too great to consider that material suitable for shipboard or other confined structure applications requiring high‐temperature resistance.
Molecular weight distribution control in continuous “living” polymerizations through periodic operation of the monomer feed
Authors: Meira G. R. , Johnson A. F. 
Published: December 2004

AbstractThe main objective of the work is to explore the problem of producing polymers of any desired molecular weight distribution (MWD) in isothermal, solution, “living”, anionic polymerizations carried out in continuous tubular reactors. For this purpose, a novel control scheme was designed and implemented, which involves the periodic operation, of the monomer solution flow rate, with the flow profile automatically derived from the required MWD and other data. For experimental validation, a polymerization rig was especially built that included a process computer and an automatic gel permeation chromatograph. The chromatograph permitted the measurement of the MWD of the reactor effluent in a matter of minutes and the process computer was employed to implement the control policies and to perform the chromatograph data acquisition and reduction. In spite of the practical problems encountered, experiments showed at least a semi‐quantitative validity of the method.
Circular couette flow of a polymerizing fluid
Authors: Lindt J. T. 
Published: December 2004

AbstractFlow of a polymerizing fluid between rotating concentric cylinders has been analyzed theoretically. A solution has been obtained employing a finite difference method. Using a RIMtype (reaction injection molding) urethane system as an example, the velocity, temperature, and NCO group concentration fields have been described as functions of time. A numerical example is given to demonstrate the applicability of the present analysis to reactive processing and viscometry. The mixing characteristics and the flow rate associated with circular drag flows involved, e.g., in reactive extrusion, have been shown to depend strongly on the operating conditions. It has also been demonstrated that the range of applicability of Couette viscometers to fast curing systems may be limited by the interfering time‐dependent temperature gradients involved. It has been concluded that analysis of the. present nature provides a useful design and evaluation tool applicable to Couette flow problems in reactive processing and viscometry.
Studies on structural foam processing. IV. Bubble growth during mold filling
Authors: Han Chang Dae , Yoo Hee Ju 
Published: December 2004

AbstractAn experimental and theoretical study was carried out to achieve a better understanding of bubble growth during the filling of gas‐charged molten polymers into a rectangular mold cavity. For the experimental study, a rectangular mold cavity (15.24 × 4.55 × 0.64 cm) was constructed, with glass windows on both sides to permit recording on a movie film of the growth of gas bubbles in the mold cavity as a molten polymer containing inert gas was injected into it. Sodium bicarbonate (generating carbon dioxide) was used as a chemical blowing agent, and the polymer used was a general purpose clear polystyrene. All experimental runs were made at isothermal molding conditions, and the injection rate was varied. It was found that, at and above a certain injection rate, little bubble formation was observed in the mold cavity during injection except at and near the moving melt front. For the theoretical study, the growth of a single gas bubble in a viscoelastic medium (represented by the DeWitt model), subjected to high injection rates, was considered by including the effects of diffusion from the liquid phase to the gas phase, interfacial tension between the liquid and the gas phases, and stress relaxation of the melt upon ejection. It was found that the level of stresses, built up in the met during injection, has a profound influence on the formation and growth of gas bubbles during the initial stage of mold filling. Also, a multichannel mold cavity was employed in order to observe the effect of processing variables on the cell size and its distribution in molded specimens. A uniform cell structure was obtained at higher injection pressures, at an optimum injection melt temperature, and with an optimum combination of blowing agent and nucleating agent concentrations.
Effect of thermal aging on impact strength acrylonitrile‐butadiene‐styrene (ABS) terpolymer
Authors: Wolkowicz Michael D. , Gaggar Satish K. 
Published: December 2004

AbstractA high speed puncture impact apparatus was used to measure impact loss in thermally aged ABS (acrylonitrilebutadiene‐styrene) as a function of time and temperature. Impact energy values decreased to a low level and degraded surface layer thickness increased as a function of aging time at three aging temperatures. Systematic removal of surface layers from thermally aged samples progressively increased impact energy values to control levels. Infrared spectroscopy, differential scanning calorimetry and molecular weight data indicate that degradation occurs in the rubber, graft and rigid phases at different times during the thermal aging period. Microscopy results show a critical degraded layer thickness which causes brittle failure of the entire sample.
Viscoelastic dissipations in the fracture of glassy polymers near their glass transition temperature
Authors: Mascia L. , Bakar M. 
Published: December 2004

AbstractThe viscoelastic energy dissipations within the bulk of the test specimen are not taken into account by classical fracture mechanics. In this study it is shown that on approaching the glass transition temperature, the amount of energy dissipated in the bulk of the specimen relative to that required to create two new surfaces can be substantial, and it may be estimated from measurements carried out on specimens with different gauge lengths. Furthermore stress relaxations can take place at the crack tip, even in absence of yielding. These can be sufficiently pronounced to eliminate stress intensification and give rise to constant fracture stress conditions.
Dimensional variations of two spherical polymeric particles during sintering
Authors: Rosenzweig N, , Narkis M. 
Published: December 2004

AbstractA quantitative “Round Neck” (RN) model based upon volume balances and considerations of surface tension phenomena is proposed for simulation of coalescence of two spherical polymeric particles; during sintering. This model and an early model developed by Frenkel are compared and evaluated against experimental data to show their suitability to simulate geometrical variations of a particle pair during sintering.
The fracture toughness of polypropylene containing poly(ethylene terephthalate) fibers
Authors: Hamer J. W. , Woodhams R. T. 
Published: December 2004

AbstractThe fracture toughness of polypropylene was increased tenfold by the addition of 30 volume percent of chopped poly(ethylene terephthalate) rovings without any appreciable sacrifice in strength or modulus. The resulting fracture toughness was independent of temperature to −40°C. For maximum effectiveness the rovings must be integrated so that the component filaments cannot disperse during the processing and injection molding stages. The three different methods employed to measure fracture toughness showed good correlation with each other and confirmed the general utility of the Izod test (with slight modification) as a measure of fracture energy. The increased toughness was attributed almost entirely to frictional energy losses during fiber pullout. Polyester fibers can be useful additives for increasing the fracture toughness of brittle resins where processing temperatures do not preclude their use.
Poly(n‐Butyl acrylate)/polystyrene interpenetrating polymer networks and related materials. II. Aspects of molecular mixing via modulus‐temperature studies
Authors: Yeo J. K. , Sperling L. H. , Thomas D. A. 
Published: December 2004

AbstractThe glass transition, rubbery modulus, and tensile behavior of poly(n‐butyl acrylate)/polystyrene interpenetrating polymer networks (IPN's), semi‐1 IPN's, and their corresponding random copolymer networks were studied as a function of both composition ratio and crosslink density. Two temperatures were selected for analysis: 25°C, halfway between the two transition temperatures, and at 160°C., in the rubbery plateau region. The modulus data at 25°C were compared with wellknown composite models. The moduli of the IPN's and semi‐1 IPN's lie close to the Davies model in the polymer II rich region but follow the Budiansky model in the polymer I rich region. In one interpretation of the Coran‐Patel model, a phase inversion takes place around ϕ2 = 0.8, which is higher than the composition at which the phase connectivity of polymer II begins to appear, ϕ = 0.5, via electron microscopy studies. The rubbery modulus behavior of the full and semi‐1 IPN's follow the equation of Siegfried, et al. reasonably well, which considers the deformation effect of polymer I in terms of the rubber elasticity front factor.The stress‐strain behavior of both the full and semi‐1 IPN's was similar to that of toughened plastics at polymer II rich compositions, and to that of reinforced elastomers at polymer I rich compositions.