bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms of polymer crystallization from flowing solutions
Authors: Acierno D. , La Mantia F. P. , Marrucci G. 
Published: December 2004

AbstractThe recent experimental results on flow‐induced crystallization by Pennings and coworkers show that extremely rigid polyethylene fibers can be obtained in a shear flow. On the other hand, the mechanism by which these flow‐induced crystals are produced is still open to investigation. In this work a few aspects of fibrous crystal growth are theoretically investigated. The molecular dynamics of chains partly attached to the crystal and partly immersed in the solution is considered. The influence of temperature and of geometrical factors is also discussed.
Solubility of vinyl chloride in poly (vinyl chloride) in a water slurry
Authors: Scamehorn John F. , Yang Kang 
Published: December 2004

AbstractThe solubility of vinyl chloride (VCM) vapor in poly (vinyl chloride) (PVC) in a water slurry has been measured between 55 and 65°C. The heat and entropy of sorption were shown to be very close to those of condensation. The solubilities measured in this study were higher than those obtained in other studies on dry PVC and PVC latex. The interaction parameter (x) in the Flory‐Huggins equation has been shown to vary between 0.34 and 0.61 over the composition range studied. The effect of ageing the slurry in the presence of VCM is also discussed.
Recycling of polyurethane and polyisocyanurate foam
Authors: Ulrich Henri , Odinak A. , Tucker B. , Sayigh A. A. R. 
Published: December 2004

AbstractHeating of isocyanate derived foams with glycol mixtures is a simple and economically attractive recycling process. The process is emission free, not sensitive to varying product mixes and the obtained polyols can be completely reused in the manufacture of rigid polyurethane or polyisocyanurate foam.
Effects of titanate coupling agents on the rheological and mechanical properties of filled polyolefins
Authors: Han C. D. , Sandford C. , Yoo H. J. 
Published: December 2004

AbstractAn experimental study was carried out to investigate the effects of titanate coupling agents on the rheological properties of p articulate‐filled polyolefin melts. Inorganic fillers used were CaCO3, talc, and fiberglass, and polyolefins used were high‐density polyethylene (HOPE) and polypropylene (PP). It was found that the addition of the coupling agent TTS to the PP‐CaCO3 and PP‐fiberglass systems reduced the melt viscosity considerably, whereas the addition of the coupling agent ETDS‐201 to the PP‐talc and HDPE‐talc systems affected the melt viscosity very little. Also carried out was an injection molding study to investigate the effects of different inorganic fillers and the titanate coupling agents used on the mechanical properties of the injection molded specimens. It was found that addition of titanate coupling agents generally resulted in reduced modulus and tensile strength, and increased elongation and impact strength of the filled systems. The PP‐CaCO3‐TTS and HDPE‐talc‐ETDS 201 systems were found to have impact strength improved by approximately 100 percent with the addition of a titanate coupling agent. The PP‐CaCO3‐TTS samples have ultimate tensile elongation approaching that of virgin PP.
Computation of the creep behavior of thermoplastics
Authors: Overath F. , Menges G. 
Published: December 2004

AbstractThe dimensioning of structural parts made of plastics requires the knowledge of the material parameters which depend on the processing and, loading conditions. In this paper, the possibility of describing the stress‐, temperature‐, and time‐dependent deformation behavior of thermoplastics below the linear viscoelastic limit is presented, using simple exponential functions. The formal relationship of the systems of equations have been ascertained based on a large number of experimental results. They enable a mathematical description of the deformation behavior of the material considered with sufficient accuracy for engineering requirements. This is based on parameters for creep experiments with three different stresses, at constant temperature, extending to 102 h. One experimental series extended to 103 h. As shown in examples, based on these experimental results, the computation makes possible a predetermination of the deformations obtained with the time‐factors of 102 to 103. The temperature can vary within the nearly linear region of the semi‐logarithmic shear modulus‐temperature curve. Within the variation of the stress, cyclic changes of the loading can also very simply be taken into account using Boltzmann's superposition principle. Principally, the computation can be carried out using any auxiliary means which contains the exponential function xy. Simple programmable pocket computers allow an automatic calculation.
Geometry of fully wiped twin‐screw equipment
Authors: Booy M. L. 
Published: December 2004

AbstractThe cross section geometry of fully wiped corotating twin screws is derived from simple kinematic principles. A pair of screws can have identical cross sections with each screw running at the same speed, or they can have an unequal number of tips and rotate at different speeds. The more conventional case of equal cross section is reviewed in detail, showing how screw diameter, centerline distance, lead, and number of tips influences design, net volumes, and surface areas. The screw cross section is unique for a given diameter, centerline distance, and number of tips. The construction of the cross section is shown, both for pairs of identical screws, and for screws with a speed ratio. Maps are provided to show applicability of screws with 1, 2, and 3 tips.
Influence of low density polyethylene quality on extrusion coating processability
Authors: Honkanen A. , Bergström C. , Laiho E. 
Published: December 2004

AbstractIn order to obtain explicit information about the influence of different low density polyethylene (LDPE) quality parameters on extrusion coating processability, a test run was made with an autoclave reactor and the products were investigated. All the grades manufactured had melt indices (MI), densities, molecular weight distributions (MWD), and degrees of long chain branching(LCB) typical of commercial extrusion coating grades. The processability characteristics studied were maximum line speed and neck‐in. The influence of MI, density, and extrusion melt temperature were systematically investigated. It was found that the maximum line speed rose with increasing MI, density, and extrusion melt temperature, and that an increasing extrusion melt temperature led to a growing difference between the maximum line speed at a constant coating thickness and the maximum line speed at a constant screw speed. Neck‐in was found to increase with increasing MI, increasing density, and increasing coating thickness. These effects were more pronounced at higher extrusion melt temperatures. When using the extrusion temperature needed to achieve a certain line speed for each grade, the influence of MI on neck‐in was practically non‐existent.
Kinetics of fast (RIM) urethane polymerization
Authors: Richter E. B. , Macosko C. W. 
Published: December 2004

AbstractThe kinetics of the dibutyltin dilaurate catalyzed bulk polymerization of 4,4′‐diphenylmethane diisocyanate (MDI) with poly‐ϵ‐caprolactone were studied by infared spectroscopy and adiabatic temperature rise. The overall reaction order was found to change from 3/2 to 2 with increasing temperature. At temperatures above 80°C, the order with respect to catalyst was found to decrease with concentration from 1 to 1/2. The results were consistent with a Michaelis Menten type kinetic scheme.
A model viscoelastic fluid
Authors: Boger David V. , Nguyen Hang 
Published: December 2004

AbstractShear stress and first normal stress difference data are presented for materials which exhibit a constant viscosity and yet at the same time exhibit elasticity levels of the same order as polymer melts. Flow pattern observations in circular die entry flows in conjunction with independent shear and normal stress measurement strongly suggest that these fluids would make excellent model fluids for melt studies. Studies in which the influence of elasticity in the absence of shear thinning and fluid inertia can easily be made. Furthermore it is clearly shown that a realistic solution to the die entry flow problem is not obtained using second order flow theory. In the second order region the secondary cell is observed to be almost identical in size to the cell observed for an inelastic Newtonian fluid in creeping flow. Marked growth in the secondary cell as a function of elasticity is not observed until the shear rates exceed the region of second order behavior. This growth in cell size as a result of elasticity is followed at higher shear rates by a spiraling flow instability like that observed for some polymer melts.
The non‐linear viscoelastic properties of molten polymers and concentrated solutions
Authors: Brereton M. G. 
Published: December 2004

AbstractFor polymer melts and concentrated solutions highly nonlinear effects dominate all aspects of both the transient and steady state mechanical behavior. The first part of this paper will review the salient features of the experimental results and focus attention on those common features which should be understood in a coherent manner. The various constitutive equations, especially the integral representations that have been proposed to describe polymer melts will also be discussed. They fall roughly into three classes: those where the relaxation function depends on the deformation rate, deformation, or stress history. Evidence will be presented which indicates that the stress history rather than the deformation history may be the more relevant variable to account for the non‐linearities. The last part of the paper will briefly review the theories that have been proposed to understand the mechanism for non‐linear behavior at the microscopic level and the influence of molecular weight and concentration.
Tensile, impact and fatigue behavior of an amine‐cured epoxy resin
Authors: Kim S. L. , Skibo M. D. , Manson J. A. , Hertzberg R. W. , Janiszewski J. 
Published: December 2004

AbstractAlthough crosslinked networks are commonly used as adhesives and composite matrixes, structure‐property relationships are not as well established as with thermoplastics. For this reason, an extensive study was begun to systematically examine effects of stoichiometry, morphology, and distribution of crosslink density on viscoelastic behavior and ultimate properties. The system selected was based on a bisphenol‐A‐type epoxy cured with methylene dianiline. This paper describes and discusses results obtained for resins in which the amine/epoxy ratio ranged between 0.7 and 2.2. In agreement with reports by others, the tensile strength, modulus, and ultimate elongation were relatively insensitive to stoichiometry but did not show slight maxima or minima when the amine was somewhat in excess. Impact strengths, tensile energies‐to‐break and fracture toughness were, in contrast, quite sensitive, though the patterns of each differed significantly. Both fracture toughness and the stress intensity factor required to drive the crack at a given rate varied directly with the amine/epoxy ratio, as did estimates of the characteristic flaw size. Fatigue striations were observed on the fracture surfaces and corresponded to the incremental advance of the crack in one loading cycle.
On the use of acceleration waves to characterize the dynamic response of non‐linear viscoelastic materials
Authors: Nunziato Jace W. 
Published: December 2004

AbstractWe consider the analysis of data obtained in one‐dimensional acceleration wave experiments on a non‐linear viscoelastic material and discuss how such data can be used to characterize the dynamic response of the material. To begin, we review briefly the general theory of one‐dimensional motions in viscoelastic materials and the methods employed to generate and observe acceleration waves in a material sample. We then discuss two methods of data analysis, a wave front analysis and a wave profile analysis, and indicate the type of information each analysis provides with regard to the dynamic properties of the material. Finally, using a known model for poly(methyl methacrylate) in a finite‐difference, Lagrangian wave‐propagation code, we calculate acceleration wave profiles at several locations in the sample and, treating these profiles as “experimental” data, we then illustrate how data from three or more acceleration wave experiments can be used to formulate a specific viscoelastic constitutive model for the material.
The effect of temperature on compressive fatigue of polystyrene
Authors: Weaver Judith L. , Beatty Charles L. 
Published: December 2004

AbstractCompressive fatigue experiments have been designed to compare this long term mechanical life property with shorter term stress‐strain behavior. Fatigue lifetime curves can be represented by three distinct regions. The fatigue failure curves shift to shorter lifetimes and lower stresses as temperature is increased. The results are discussed in terms of the Zhurkov model of static fatigue failure. Using a Coulomb‐Navier yield criterion modified rate expression, it is clear that activation energy and activation volume are functions of temperature. A change in temperature dependence of activation energy and endurance limiting stress occurs near the β transition suggesting that this molecular process is related to the fatigue process. The nearly identical dependence of fatigue and stress‐strain activation energies and activation volumes with temperature suggest that both deformation processes may be controlled by a similar mechanism, i.e., localized plastic deformation. Utilizing these concepts, a simple model of fatigue allows correlation of the endurance limiting stress and the number of stress cycles at the endurance limiting stress with measures of resistance to plastic flow as determined from stress‐strain data for this polystyrene. These data are used to project the longest and shortest mechanical fatigue lifetimes for these deformation conditions.
Scission and crosslinking during oxidation of peroxide cured EPDM
Authors: Landi V. R. , Easterbrook E. K. 
Published: December 2004

AbstractThe chemorheology of polymers prepared by peroxide curing terpolymers of ethylene propylene and diene monomer (EPDM) was studied at 375°F in air. Measurements were conducted on terpolymers containing dicyclopentadiene (DCPD), ethylidene norbornene (ENB) or 1,4‐hexadiene (HD) and also on copolymers. Effects of the level of dicyclopentadiene were investigated. A linear relationship is found between crosslinks formed during oxidation and chain scissions. At low termonomer level and in copolymers, this relationship is linear only during the early stages of oxidation. Results are consistent with a kinetic model in which crosslinking sites and scissioning sites on the polymer compete for free radicals which propagate the oxidative chain reaction. Termonomer units apparently act primarily as crosslinking sites with the tendency to crosslink being substantially greater in DCPD than ENB and HD. The number of crosslinks per scission derived from stress relaxation correlates well with elongation to failure retained after air aging 3 days at 350°F. Adjustment of termonomer level can lead to a ratio of crosslinking to scission which strikes a balance between softening of copolymer and embrittlement of some terpolymers at elevated temperature.
Distinguishing amorphous polymer blends from copolymers by wide angle X‐ray diffraction
Authors: Riga Alan T. 
Published: December 2004

AbstractAmorphous homopolymer blends were differentiated from the corresponding random copolymers with wide angle X‐ray diffraction (WAXRD) using the diffraction angle and the band width at one‐half peak maximum. The diffraction angle was also used to determine the composition of copolymers and of mixtures of homopolymers. A procedure has been developed to predict the WAXRD patterns of polyblends and/or random copolymers based on those of the corresponding homopolymers.
Multistage latex particle size analysis by disc centrifuge photosedimentometry
Authors: Seidewand Robert J. , Erickson James R. 
Published: December 2004

AbstractCharacterization of a heterogeneous latex polymer synthesis requires quantifying the association of successive stage compositions with the previous stage latex seed particles. A new method for performing this analysis is presented for uniform sized latex particles by use of a Joyce Loebl disc centrifuge photosedimentometer. An iterative procedure is employed to solve a problem of unknown particle density when a successive polymerization produces new latex particles. The procedure is applicable regardless of the monomer compositions of the various stages and eliminates problems encountered with electron microscopy of soft deformable latex particles.
Polymer blends containing poly(vinylidene fluoride). Part IV: Thermodynamic interpretations
Authors: Paul D. R. , Barlow J. W. , Bernstein R. E. , Wahrmund D. C. 
Published: December 2004

AbstractA summary of the transitional behavior of blends containing poly(vinylidene fluoride), PVF2, and various oxygen‐containing polymers is presented. These data are used to establish the presence of a single miscible amorphous phase. The depression of the PVF2 melting point in those blends judged to be miscible is analyzed using standard thermodynamic arguments to determine the heats of mixing between the amorphous diluents and the PVF2. These heats of mixing are exothermic indicating the presence of strong interactions between the binary pairs. A comparison between the observed interaction strengths and the dipole moments of the various diluents suggests that the exothermic heats of mixing are the result of strong dipole‐dipole interactions. Nearly all the miscible blends with PVF2 show Lower Critical Solution Temperature (LCST) behavior. The direct correlation between the temperature location of this phase instability and the observed interaction strength suggests that the instability is more the result of enthalpic considerations than entropic ones.
Effects of environment on the mechanical properties of plastics under high pressure
Authors: Trent John S. , Moet Abdelsamie Y. , Miles Mervyn J. , Baer Eric 
Published: December 2004

AbstractPolystyrene (PS), high‐impact polystyrene (HIPS), and polyethylene (PE) have been investigated studying the pressure dependence of stress‐elongation behavior in tension over the range from atmospheric pressure to four kilobars at room temperature. The effect of strain rate was also observed for PS specimens. Tensile deformation of PS and HIPS has shown that the pressure‐transmitting fluid (silicon oil) acts as a stress crazing and cracking agent. Non‐sealed specimens of PS showed a brittle‐to‐ductile transition at 2.95 kbar while specimens sealed from the environment showed the same transition at only 0.35 kbar. Scales HIPS and PE specimens exhibited ductile behavior at all pressures. The extent of plastic deformation for PE was affected when specimens where exposed to the silicon oil environment. Surprisingly, HIPS exposed to the oil exhibited two transitions as the applied hydrostatic pressure was raised: a ductile‐to‐brittle followed by a brittle‐to‐ductile transition. Analysis of the stress‐elongation curves for sealed PS and HIPS specimens indicated that the pressure dependency of craze‐initiation stress differs from that of shear band initiation stress. The brittle‐to‐ductile transition occurred when the initiation stresses of both processes became equal. The principal stress for craze initiation showed almost no pressure dependency, suggesting that crazes initiate when the principal stress level of the tensile specimen reaches a critical value irrespective of the applied hydrostatic pressure.
Thermochemical characterization of some thermally stable thermoplastic and thermoset polymers
Authors: Kourtides Demetrius A. , Gilwee William J. , Parker John A. 
Published: December 2004

AbstractThe thermochemical and flammability properties of some thermally stable polymers considered for use in aircraft interiors are described. The properties studied include: (a) thermomechanical properties such as glass transition and melt temperature; (b) dynamic thermogravimetric analysis in anaerobic environment; (c) flammability properties such as oxygen index, flame spread and smoke evolution; and (d) selected physical properties. The thermoplastic polymers evaluated included polyphenylene sulfide, polyaryl sulfone, 9,9‐bis(4‐hydroxyphenyl)‐fluorene polycarbonate‐poly(dimethylsiloxane) and polyether sulfone. The thermoset polymers evaluated included epoxy, bismaleimide, a modified phenolic and polyaromatic melamine resin. These resins were primarily used in the fabrication of glass reinforced prepregs for the construction of experimental panels. Test results and relative rankings of some of the flammability parameters are presented and the relationship of the molecular structure, char yield, and flammability properties of these polymers are discussed.
Mineral fillers in low density‐polyethylene films
Authors: Arina Markku , Honkanen Arto , Tammela Viljo 
Published: December 2004

AbstractThe use of fillers is an established method of modifying the properties of plastics. The recent increase in prices of plastic raw materials and the new developments in compounding technology have heightened the interest of the plastic industry in compounds of fillers and polyethylene. This article discusses briefly the literature dealing with the effect of fillers on the properties of polyethylene, and research carried out on the effects of different mineral fillers, talcs, micas, clays, wollastonite and dolomite on the many properties of low density polyethylene films. The fine grade talcs have proved to be better than the other fillers with respect to most film properties. The platy talcs decreased the oxygen permeability by as much as 80 percent and the water vapor transmission rate by as much as 70 percent. With talcs, clays and dolomite the yield strength increased but with all fillers the tensile strength at break weakened with increasing filler content. A low elongation at break and a low tearing, resistance indicate the brittleness of the films especially at high filler contents (over 30 wt percent). The coefficients of friction decreased considerably with all fillers and a significant improvement in printability was achieved. However, none of the fillers had more than a very minor effect on the heat sealability of low density polyethylene.
Radical formation and deformation in poly‐p‐(2‐hydroxyethoxy) benzoic acid fibers
Authors: Nagamura T. , Devries K. L. 
Published: December 2004

AbstractRadical generation during tensile deformation of poly‐p‐(2‐hydroxyethoxy) benzoic acid (PEOB) fibers was studied by electron spin resonance techniques under various stretching conditions. Primary phenoxy radicals were detected at room temperature, indicating main‐chain rupture during mechanical loading. The kinetics of phenoxy radical formation were observed at constant strain, constant load, constant strain‐rate, and in constant load rate experiments. The effect of strain rate on the radical formation was found to be larger in this sample than was observed in Nylon 6. These results coupled with other experimental observations have yielded information on a basic structural model and improved insight into the basic molecular mechanism responsible for deformation and fracture.