bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological behavior of two‐phase polymer melts
Authors: Han C. D. , Yu T. C. 
Published: December 2004

AbstractRheological behavior of dispersed two‐phase polymer melts has been investigated by means of a capillary rheometer. The two‐phase systems chosen for study were blends of two polymers: high‐density polyethylene and polystyrene, which are incompatible in the molten state. In order to investigate the state of dispersion, photographs were taken of the microstructure of extrudate samples, showing that the polystyrene forms long fibers or droplets as a discrete phase dispersed in the polyethylene which forms a continuous phase. Measurements were made of the axial pressure distributions of the two‐phase molten polymers flowing through circular tubes, which permit one, according to the theory advanced by Han, to determine viscous and elastic properties of the melts. Also measured was melt die swell ratio. It has been found from the two independent experimental techniques that there exist a maximum and/or minimum elastic property at a certain blending ratio, and that the elastic property decreases first with L/D ratio of a capillary and then levels off.
Cold rolled ABS. Part 1: The effect of rubber particle size on the tensile properties of ABS before and after cold rolling
Authors: Grancio M. R. 
Published: December 2004

AbstractThe effect of rubber particle size on the tensile properties of rolled and unrolled acrylonitrile‐butadiene‐styrene has been studied by considering model systems consisting of mixtures of a small particle (0.1 micron diam) rubber, S, and a large particle (0.56 micron diam) rubber, L, in an SAN matrix. Before rolling, tensile toughness is characterized by crazing. While both rubber induce matrix crazing, ABS systems containing only the S rubber exhibits early failure due to crack formation, before crazing is propagated very far along the tensile axis. The inefficiency of the small particle rubber is interpreted in terms of high composite yield stress and insufficient distance between particles to allow craze branching. The efficiency of the small particle rubber is improved via the addition of a small amount of large particle, L, rubber to the composite or by a slight degree of cold rolling, both of which enhance craze propagation in the tensile direction. With further rolling, the tensile deformation mode changes from one of localized crazing, which is propagated, to one of uniform deformation, which occurs without crazing.
Predicting melt flow instability from a criterion based on the behavior of polymer solutions
Authors: Boger D. V. , Williams H. Leverne 
Published: December 2004

AbstractA criterion, based on the behavior of polymer solutions, is developed and applied for the prediction of the onset of flow anomalies observed at the capillary entrance for polymer melts. It is shown that a direct correspondence exists between the flow anomalies observed for polymer solutions and polymer melts. The onset of these anomalies can be correlated with a critical Weissenberg number which is consistent with the equality of the shear wave velocity and friction velocity. This critical condition can be employed to derive expressions useful for predicting the critical recoverable shear and critical shear stress for melt fracture.
Some aspects of orientation in injection molded objects
Authors: Wales J. L. S. , Van Leeuwen Ir J. , Van Der Vijgh R. 
Published: December 2004

AbstractThe birefringences of injection molded plates and the birefringence during steady, isothermal shear flow were compared for some amorphous polymers. The materials studied were a polystyrene, a “toughened” polystyrene and an acrylonitrile‐butadiene‐styrene copolymer. The birefringence of the plates, notably the maximum value for the average over the thickness was found to be related to the shear stress at the cavity wall that had occurred during the mold filling process. This relationship was independent of temperature. To a good approximation, it was also the same as the relationship between the flow birefringence and the shear stress at the wall in isothermal channel flow. It thus appears that the anisotropy of injection molded objects is dominated by the shear stresses during the mold filling process regardless of the temperature and of the macroscopic rate of deformation.
Microfibers within fibers: A review
Authors: Tucker Paul , George Waller 
Published: December 2004

AbstractLiterature relating to the fundamental nature of the fibrous state is reviewed with the goal of illustrating evidence for the existence of a possibly fundamental morphological unit, the elemental microfiber or fibril. Following a short summary of the rather well documented situation in natural fibers, the problem of the microfiber in synthetic fibers is probed in terms of phenomena in solution and bulk polymeric systems. The reviewed literature indicates the existence of unique, elemental microfibers in synthetic fibers is largely tenuous; however, there is wide evidence of the existence of complex elongated structures axially aligned within macrofibers which future work may resolve into a central microfiber. The structural complexity appears to simplify for transformations occurring in high shear fields. This review covers articles through 1971, and it is notable that in 1971 approximately 100 articles of high relevance appeared in major journals.
Block and graft polymers their synthesis, especially by living polymer technique, and their properties
Authors: Szwarc Michael 
Published: December 2004

AbstractThe various structures encountered in block and graft polymers are reviewed and a nomenclature useful for the description of these macromolecules is proposed. The concept of living polymers is elucidated and its ramifications discussed. It is shown how greatly the control of polymerization and the uniformity of the products is improved when living polymers are used as the reagents. Their application in the synthesis of block and graft polymers is illustrated by numerous examples. Other synthetic techniques yielding block and graft polymers are briefly sketched, their advantages and shortcomings being considered. Properties of block and graft polymers are described, special attention being devoted to the problems of mesomorphic phases and to the morphology of block polymers. The incompatibility phenomena observed in block and graft polymer systems are compared with those encountered in studies of the polymeric blends.Finally, the present and future applications of block and graft polymers are considered and their potential evaluated.
Mechanical relaxation phenomena in polyimide and poly(2,6‐dimethyl‐p‐phenylene oxide) from 100°K to 700°K
Authors: Lim T. , Frosini V. , Zaleckas V. , Morrow D. , Sauer J. A. 
Published: December 2004

AbstractExisting dynamic mechanical relaxation data on two polymers containing aromatic groups in the backbone chain, viz., polyimide PI, and poly(2,6‐dimethyl‐p‐phenylene oxide), PDMPO, are reviewed and new data bearing on specimen purity and water content are presented. It is demonstrated that three separate relaxation processes are normally present in both polymers in the temperature range from about 100–400°K. The lowest temperature relaxation, designated γ, occurs in the 100–180°K range and is considered to arise from limited rotational oscillation of some phenylene rings about the 1,4 axis. Another relaxation process, designated β arises from the presence of water in the polymer. Its strength increases with increase of water content, its activation energy is about 10–12 kcal/mole, and it occurs in the 180–190°K range at 1 Hz. A higher strength secondary glass relaxation process, designated β*, occurs in the 280–400°K range at usual measuring frequencies (1 Hz to 104 Hz). This relaxation is thought to be associated with the combined reorientational motion, of rings and connecting atoms of the monomer unit in “defect” regions, or regions of poor chain packing. As such, its position is affected by sample history. Both polymers also show a rise in damping in the high temperature region indicative of additional main chain motions. In addition to the above relaxations, PDMPO shows a δ‐relaxation below liquid nitrogen temperatures, associated with onset of Me rotation and PI shows an additional small relaxation near 500°K.
Kinetics and thermal characterization of thermoset cure
Authors: Kamal M. R. , Sourour S. 
Published: December 2004

AbstractThe differential scanning calorimeter (Perkin‐Elmer DSC‐1) is used to characterize the cure of a general‐purpose polyester during isothermal and scanning experiments. The technique is based on a new proposed model for the kinetics of isothermal cure. The model yields results which are in good agreement with experimental isothermal rate of reaction and integral heat of reaction data. It also gives some information about the residual reactivity of the sample after an isothermal cure experiment. With the aid of the proposed kinetic model, it is possible to obtain integral heats of reaction and rates of heat generation at different temperatures during a scanning experiment. The difference between the rate of heat input to the sample and the heat of reaction at any instant during scanning may be used to calculate the specific heat of the sample at the same instant. Specific heat data show two maxima during each scanning experiment. These maxima may be associated with transitions occurring during cure in the melt and rubbery states.
Synergistic interaction in zinc/epoxy/phosphite stabilization of polyvinyl chloride
Authors: Deanin Rudolph D. , Foss Robert M. , Gilbert Paul G. , Guerard Ronald F. , Muccio Edward A. 
Published: December 2004

AbstractZinc laurate was a powerful but short‐lived primary stabilizer. Epoxidized soybean oil, catalyzed by a trace of zinc, was a fairly good primary stabilizer. Organic phosphite ester served primarily to prevent premature failure due to zinc; phosphite/zinc mol ratio of 4.5/1 was optimum. These combined effects are consistent with present theories of stabilizer synergism, and also suggest some further possible mechanisms. Practically, the 3‐component system offers a low‐cost, efficient, non‐toxic stabilizer for plasticized polyvinyl chloride.
Flow of polymer melts in a disc‐type extruder and in rotational devices of the “cone‐plate” and “plate‐plate” type
Authors: Kocherov V. L. , Lukach Yu. L. , Sporyagin E. A. , Vinogradov G. V. 
Published: December 2004

AbstractThe flow pattern of a polyethylene melt in the working gap of a disc‐type extruder has been visualized. It is shown that there is complex circulating flow in the working gap of the extruder. The flow lines are spirals of Archimedes. An investigation into the qualitative picture of the flow of a polyethylene melt in rotational devices of the “plate‐plate” and “cone‐plate” type showed that in such devices a complex circulating flow is also realized and the flow lines are spirals of Archimedes.
Chlorinated polyethylene modification of blends derived from waste plastics Part I: Mechanical behavior
Authors: Paul D. R. , Locke C. E. , Vinson C. E. 
Published: December 2004

AbstractRecycling of waste plastics as a blend of generic types is attractive since a difficult separations problem is avoided. However, blends of incompatible polymers are frequently very brittle and cannot be considered for many applications. Additives which modify the blend to give it ductility may provide a solution to this problem. Chlorinated polyethylene (CPE) made by a slurry process has been suggested for this application by Schramm and Blanchard. Further documentation of the effectiveness of this approach is given here. Addition of CPE to such a blend generally increases the elongation at break and the energy to break very dramatically with ordinarily some loss in strength and modulus. This approach works most effectively in blends of high polyethylene and poly(vinyl chloride) content. Three grades of CPE were studied here which revealed that the specific structure of the CPE molecule is a factor. The effectiveness of CPE for blend modification is believed to derive from the graded molecular structure acquired during chlorination.
Flow and heat transfer in screw extruders: I. A variational analysis applied in helical co‐ordinates
Authors: Nebrensky J. , Pittman J. F. T. , Smith John M. 
Published: December 2004

AbstractA variational analysis is applied in helical co‐ordinates to the problem of a developed, steady‐state flow in a screw extruder. The functional involves only two dimensionless coordinates and is suitable for minimisation, e.g. by the finite element method. It is applicable to non‐isothermal, purely viscous flows and contains terms representing effects of inertia, convective and conductive transport of heat, pressure gradient, and viscous dissipation. The analysis takes account of the true helical geometry and involves assumptions only in taking the fluid density, specific heat and thermal conductivity of the fluid to be constant, in regarding the fluid to be homogeneous and isotropic, and in simplifying the pressure distribution.
Yielding of polycarbonate and polysulfone in creep and stress‐strain
Authors: Matz David J. , Guldemond William G. , Cooper Stuart L. 
Published: December 2004

AbstractA modified Eyring rate expression based on an asymmetrical potential energy barrier is used to predict the onset of plastic yield in glassy polymers. Equations for the prediction of plastic yield delay times in creep and yield stresses in constant rate of strain testing are developed and compared to experimental data for samples of polycarbonate and polysulfone with various thermal histories. The two equations accurately fit the experimental results for a suitable choice of parameters. Parameters from the creep data can be used to predict yield stress values in constant rate of strain testing. Variation in simple thermal history changes the model parameters in a way that is qualitatively accounted for from a physical interpretation of the constants.
Differential scanning calorimetry of the epoxy cure reaction
Authors: Prime R. Bruce 
Published: December 2004

AbstractFrom a review of the literature it is shown that kinetics from programmed heating rate experiments are often in serious disagreement with published isothermal data. In every case, including the present, the dynamic kinetic parameters measured on epoxies are significantly larger than the isothermal. Use of a dynamic rate equation provides good agreement between the two experiments. It is also shown that the Kissinger method is correct when applied to DSC of epoxies.
Correlation between uniaxial and shear creep of thermoplastics
Authors: Benham P. P. 
Published: December 2004

AbstractCreep data in uniaxial tension, compression and shear on PVC, PMMA, and PP sheet were used to test analytical correlating procedures. It was shown that shear and uniaxial creep could be closely related using the concept of shear stress and shear strain on octahedral planes. This correlating procedure was only effective if due allowance was made for the different creep response in simple tension and compression for each of these materials. It was also shown that the relationship between the viscoelastic creep moduli and strain ratio, which is stress and time dependent, has the same form as the analogous relationship between the linear elastic constants.
Gel permeation chromatography: A guide to data interpretation
Authors: Evans J. M. 
Published: December 2004

AbstractThe importance of data produced by gel permeation chromatography (GPC) in polymer engineering is emphasized. The steps involved in deriving a differential molecular weight distribution curve (dMWD) from the chromatogram obtained by GPC are outlined. Each step is described, indicating its importance. Several viscosity‐molecular weight relationships, useful in the production of relevant calibration curves from the polystyrene calibration, are included. The presentation of results and experimental procedures are given.
Theoretical prediction of pressure loss in pressurized plastic containers
Authors: Fenelon Paul J. 
Published: December 2004

AbstractRelations describing the time dependence of pressure loss in pressurized plastic containers are presented and discussed. These relations are expected to be useful in predicting the shelf life performance of pressurized plastic containers in applications such as aerosol and carbonated beverage containers. The time dependence of pressure loss in pressurized plastic containers is shown to be dependent on at least three independently contributing factors, namely gas absorption, gas permeation, and material viscoelastic characteristics. The influence of these three qualities is shown to be time dependent and expressions are presented which allow the relative importance of each to be assessed in terms of quantities that are conveniently measured in the laboratory. The pitfalls associated with defining quantitatively the effectiveness of a plastic barrier material as predicted by a steady state analysis is discussed. It is shown that such steady state analysis may be extremely misleading and may not necessarily be a measure of a material's time dependent qualities.
Polyimides: Effect of molecular structure and cure on thermomechanical behavior
Authors: Gillham J. K. , Gillham H. C. 
Published: December 2004

AbstractThe thermomechanical spectra (∼0.5 → 1 cps) of systematically related polyimides synthesized from four aromatic dianhydrides and eleven aromatic diamines are discussed with respect to structure‐property relationships and cure. In displaying two main transitions, Tg and Tβ, most of the polymers behave as amorphous materials such as polymethylmethacrylate. A different mechanism for the relaxations is invoked which involves more intermolecular interaction for those polymers (from pyromellitic dianhydride) which give more complex behavior. Difficulties in obtaining structure‐property relationships in the field of high temperature rigid polymers are discussed in terms of defects in molecular structure, the effect of vitrification in freezing out reactions during cure, different chemical reactivities of the reactive precursor polyamic acids, and the effects of thermal reactions which occur in the vicinity of the glass transition regions.
The SPE international award address—1973 the development of impact polystyrene–a review
Authors: Amos J. Lawrence 
Published: December 2004

AbstractThe development of impact polystyrene and types of processes used is traced from its inception. Our accidental discovery of the process has resulted in the process being termed unique in that no other commercial polymerization has a like phenomenon that occurs in the shearing agitation step. The prior art and patent picture, before and after the issue of the Dow basic patent, is discussed. The litigation that has centered around the patent is reviewed. Information presented shows that this basic process for impact polystyrene has experienced an unusual degree of commercial success and has led to this family of plastics becoming of major commercial importance. These impact plastics have been accepted and used on a global basis.
Free radical formation in oriented polybutadiene during mechanical deformation below Tg
Authors: Mead W. T. , Reed P. E. 
Published: December 2004

AbstractThe tensile behavior of oriented polybutadiene at 83°K is systematically studied as a function of strain rate and pre‐test orientation. Electron spin resonance studies of radical formation are made in conjunction with the mechanical tests. Three different modes of mechanical behavior are observed (brittle, crazing and a second ductile behavior without crazing), depending on test conditions. Radical formation is observed in association with the two ductile modes of behavior. The ESR spectra obtained are attributed to a combination of allyl radicals formed by chain scission between the α‐methylene groups and peroxy radicals. The relative quantity of the two radical species present is thought to be related to the ratio of cis/trans‐isomerism. Stability of the radicals observed with time and with an increase in temperature is studied. Further studies are made of the quantity of environmental test gases absorbed during crazing.
Theoretical model for non‐intermeshing twin screw extruders
Authors: Kaplan Aharon , Tadmor Zehev 
Published: December 2004

AbstractA simple theoretical model for flow in nonintermeshing twin screw extruders has been derived. The assumptions which in single screw extruders result in the “two parallel plates” model, in twin screw extruders result in the “three parallel plates” model. The flow rate equation can be expressed, for Newtonian fluids, in terms of drag and pressure flow terms, as in single screw extrusion theory, but each term is multiplied by a geometrical factor. This factor incorporates the effect of one screw on the drag and pressure flow terms of the other. The theoretical model was experimentally verified on a 1 inch diameter Bausano twin screw extruder.
The mechanical properties of high‐density rigid polyurethane foams in compression: II. Yield behavior
Authors: Waterman N. R. , Phillips P. J. 
Published: December 2004

AbstractA series of rigid polyurethane foams of densities varying from 65 kg/m−3 to 400 kg/m−3 have been tested in compression as a function of rate and temperature. Two yield points are observed, the lower one being associated with the surface layers, the higher with the bulk of the material. The yield points may be predicted to a first approximation for the higher density foam using a model based on the buckling of a thinwalled cylinder.
Protein structures and protein fibers—a review
Authors: Huang Frank F. , Rha Chokyun 
Published: December 2004

AbstractThe biochemistry and stereochemistry of proteins are reviewed and related to molecular structure and specifically to the properties governing fiber formation. The conformation of amino acids, polypeptides and proteins are discussed. The amino acid composition of protein is considered in relation to structure, chain length and molecular weight. General descriptions are also given for typical synthetic polypeptides as well as for non‐fibrous natural proteins used in fiber manufacture. Mechanisms and modes are presented for fiber formation including a discussion of molecular criteria involving intermolecular cohesive and crystalline configurational forces which are involved in the fiber forming process. These effects are related to treatments and processes, including thermal, mechanical and chemical modifications, which can be applied to protein for the purpose of forming fibers.
The electret effect in cellulose acetate reverse osmosis membranes
Authors: Wallace Richard A. , Gable Richard J. 
Published: December 2004

AbstractThe electret potentials developed by reverse osmosis electret membranes help control the undesirable deposition of charged colloidal particles on the membrane surfaces during membrane desalination. These antifouling electret membranes should help prevent the costly flux declines normally associated with deposition of colloidal iron oxides on the reverse osmosis membrane surfaces.Homocharge and heterocharge behavior of cellulose acetate membrane electrets have been studied. Asymmetric reverse osmosis membranes and dense membrane films were studied. The homocharge and heterocharge of cellulose acetate reverse osmosis electret membranes have been explained.
Dynamic model of a plasticating extruder
Authors: Tadmor Z. , Lipshitz S. D. , Lavie R. 
Published: December 2004

AbstractA theoretical model for the simulation of dynamic operation of a plasticating extruder is proposed. The model can be recommended as a tool to study various dynamic situations of interest in the operation of an extruder. Several responses to changes in operating conditions are discussed. They indicate the occurrence of transient maximas and occasional oscillations. The controlling of flow rate by adjusting a valve at the die seems to cause temporary local high peaks in pressure, whereas its control through screw speed seems to be satisfactory.