bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of the spectrophotometer to control carbon dispersion quality in polyethylene
Authors: Howard John B. 
Published: December 2004

AbstractRenewed interest in the development of a quantitative optical technique for assessing the quality of carbon dispersion in weather‐resistant polyethylene compositions has given fresh significance to the findings of a study conducted earlier by a task group of ATSM Committee D‐20 but not previously reported in the literature. This group evolved and refined a spectrophotometric procedure which was shown to be capable of good interlaboratory reproducibility when the same film was measured by each of the participants in turn. When each laboratory prepared its own film specimen from a standard lot of pellets, however, this reproducibility dropped to a very unsatisfactory level. It was concluded that fine‐grained inhomogeneities even in compounds considered to have excellent dispersion quality preclude reproducible test results when sample weights of only a few milligrams are involved. The problem is aggravated by the difficulty of preparing thin, uniform films and complicated by a nonlinear dependence of transmission on film thickness.
Stereoregulation and stereoregular polymers
Authors: Schildknecht C. E. 
Published: December 2004

AbstractThe discovery of methods for regulating stereoisomerism in polymer synthesis, and thereby controlling polymer properties, is one of the most significant recent developments in polymer science. Polypropylenes and propylene copolymers are the outstanding products resulting already. This review includes both European and American contributions from the beginning of the idea. It emphasizes researches on polymerization of vinyl ethers and of 1‐olefms which have been most important in development of the basic concepts of stereoregulation. The review is based in part upon a paper presented at the Canadian Polymer Forum in Ottawa in September 1965.
In‐line annealing—a new approach to the extrusion of high quality rigid vinyl products
Authors: Socha Robert P. 
Published: December 2004

AbstractMost polymers exhibit a very fluid melt rheology during extrusion and can be distorted, drawn down, and cooled without building excessive residual stresses into the product. In contrast, rigid vinyl is usually extruded as a stiff, almost selfsupporting mass. Care must be taken to prevent the formation ot oriented stresses in the product which will be relieved during long periods of exposure resulting in dimensional instability and related loss of physical properties. A newly developed method of in‐line annealing has shown to be an effective means of relieving oriented stresses developed during extrusion. By use of this instrumented technique, rigid vinyl products can be controlled to much tighter shrinkage specifications in a single step process, thereby eliminating post‐annealing treatments.
Glass‐resin joint strength and their effect on failure mechanisms in reinforced plastics
Authors: Broutman Lawrence J. 
Published: December 2004

AbstractThe various methods which have been used to measure the joint strength of a glass‐polymer interface have been reviewed and the results compared. Conclusions have been made regarding the strength of polyester and epoxy joints and the role of the coupling agent in enhancing this strength. Bond strength methods discussed include the flat plate test as well as the single filament techniques. The stresses which exist at the interface in an actual comosite are calculated. The relation of the glass‐polymer joint strength to the final strength to the final strength of a glass reinforced plastic composite is dissussed. The interaction of the interface with an advancing crack is also considered.
The strain response of plastics to complex stress histories
Authors: Turner S. 
Published: December 2004

AbstractWhereas the creep behaviour of plastics is conventionally studied by the application of a simple step‐function of stress, the stress conditions encountered in service are often much more complicated. The response of a liner viscoelastic material to a complex stess history can be calculated from the step‐function response, but this is not so for plastics which are non‐liner viscoelastic. The paper considers this from a mainly experimental viewpoint and underlines the general inadequacy of the current continuum echanical approach. The sections on recovery and intermittent stressing are of particular practical importance since it is under these conditions that plastic display particulary useful characteristics.
Cause and effect in time dependent flow of thermoplastic melts—a review
Authors: Schreiber H. P. 
Published: December 2004

AbstractThe factors leading to time dependnt variations of melt viscosity during capillary extrusion of thermoplastics are reviewed. An initial increase in melt viscosity has been attributed to melt elasticity while three mechanisms are cited to account for a subsequent drop in melt viscosity, which may or may not attain a steady‐state value. These are frictional heational heating of the melt, increasing shear stress as the viscometer reservoir empties, and cain orientation. The relative importance of the mechanisms is examined for various melts and the importance of time effects is discussed in terms of their influence on standard flow evaluations, such as the melt index determination.
Laboratory evaluation of plastic pipe from a gas service field‐test installation
Authors: Kuhlmann H. W. , Leininger R. I. , Wolter Fritz 
Published: December 2004

AbstractThis article presents the background and results of the first two‐year interval test of a projected 10 or more years field gas service test of various types of plastic pipes. The study is part of a program to establish the suitability of plastic pipes for gas distribution uses. A number of short‐term laboratory tests were used to characterize the condition of the pipe after the first two‐year exposure period some, like the cursh test, are recognized and accepted methods; others, like the ring‐tensile, tensile‐impact, and the tear‐propagation tests were developed or modified for this stdy. The results show that comparatively little change had taken place in this test period; the possible exception being in the ductility of two kinds of pipe subsequent evaluation should confirm or deny this behavior.
Effect of variables in artificial weathering on the degradation of selected plastics
Authors: Kamal Musa R. 
Published: December 2004

AbstractArtificial weathering devices are used extensively by the plastics industry to aid in the prediction of the weatherability of plastic matrials. Correlations between the results of outdoor and artificial weathering, however, are poor for lack of control and understanding of the exposure variables in these devices. This work summarizs some of the results of an experimental program designed to analyze the effects of variables in artificial weathering on the preoperies of selected commercial plastics. In addition to the presentation of data establishing the importance of each of the variables in artificial weathering, a discussion of the significance of these data with regard to the selection of optimum exposure cycles is given. Furthermore, some new approaches are proposed with regard to obtaining inproved correlations between the results of outdoor and artificial exposure. Model calculations based on the proposed approaches yield a surprisingly high degree of correlation between the two types of exposure.
Time dependent crystallinity of polybutene‐1
Authors: Choi S. Y. , Rakus J. P. , O'Toole J. L. 
Published: December 2004

AbstractIsotactic Polybutene‐1 can exist in 4 different crystalline phases of varying stability of which two are of greatest importance because they are involved in solidification from the melt initially, the melt cools into an unstable crystalline phase which gradually and spontaneously transforms into a stable, stronger, stiffer, more crystalline phase over a period of days. Rate of development of mechanical properties depends on crystallinity which depends on rate of phase change. However, optical properties develop in an unusual and irregualr way that is significantly affected by external factors, suxh as pressure, temperature, fillers nucleation and geometry.
Application of the rheology of monodisperse and polydisperse polystyrenes to the analysis of injection molding behavior
Authors: Hagan R. S. , Thomas D. P. , Schlich W. R. 
Published: December 2004

AbstractMonodisperse and polydisperse polystyrenes of equal weight average molecular weight (Mw) are evaluated for melt flow behavior in an Instron capillary rheometer and for injection molding behavior in a 12 ounce in‐line reciprocationg screw injection molding machine. The influence of molecular weight distribution on the shape of the flow curves is deconstrated over a wide range of shear rate and temperature. The influence is also reflected in injection molding behavior as defined by pressure to fill or flash the mold at a given melt temperature. Studies of capillary rheometer data for correlation with injection moling beghavior indicate poor agreement when low shear rate viscosity data are used. Good agrement is foun using high shear rate viscosity data in the range 103 to 104 sec−1 Striking crossover points on melt rheology and injection colding area diagram curvs are found with the monodisperse and polydisperse polystyrenes of the same M These crossovers shift with melt temperature and make possible the determination of a “controlling shear rate” for the injection molding process. This is found to be 3500 sec−1 for short shot and 6200 sec−1 for flash with the ASTM test specimen mold used in this study.
The influence of microstructural characteristics on the failure properties of a polybutadiene system
Authors: Martin Donald L. 
Published: December 2004

AbstractThe stress‐strain characteristic of polymeric binders and solid propellants are dependent on the crosslink density, molecular weight between crosslinks, molecular weight distribution in the binder formulation, volume fraction of filler, and the interaction between the binder and filler particles. This investigation is directed toward elucidation of solid propellant microscopic response and failure mechanisms through characterization of the constitutive effects of crosslink density, molecular weight distribution and curing agent ratio in the binder formulation, and filler fraction. This was accomplished on the ERLA/PBAA propellant system through investigation of three binder formulations with the same curing agent ratio but different crosslink densities; five binder formulations with different curing agent ratios; and four formulations with up to 69.9% by volume of filler.Uniaxial stress‐strain characteristics were determined on each formulation at displacement rates of 0.2 to 20.0 in/min at isothermal test conditions ranging from 75 to −90°F. The failure characteristics of a viscoelastic material represent a curve in the three‐dimensional space of stress, strain, and time. The ultimate property data on each formulation are presented as projections of this failure curve on the stress‐strain, stress‐time, and strain‐time planes, respectively. Relationships are developed for the dependence of the stress‐time, strain‐time, and stress‐strain failure envelopes on the volume fraction of bound rubber, crosslink density, molecular weight distribution and curing agent ration in the binder component, and the volume fraction of filler.
A simple, versatile and inexpensive rheometer for polymer melts
Authors: Best D. M. , Rosen S. L. 
Published: December 2004

AbstractA simple, versatile biconical rehemoter has been developed. This device provides shear creep and creep recovery data for polymer melts over a temperature range of 200–500°F. and a range of applied shear stresses from 2 × 103 to 9 × 105 dynes/cm2.Extensive reheological data have been obtained for two samples each of polyisobutylene and high‐density polyethylene. These illustrate the value of the device in obtaining data useful for predicting and understanding the processing properties of polymer melts.
Designing against fracture in brittle plastics
Authors: Williams J. G. , Radon J. C. , Turner C. E. 
Published: December 2004

AbstractThe fracture toughness of a variety of sharply notched tension, bending and rotating disc specimens of PMMA is examined using linear fracture mechanics. It is observed that rapid fracture with a brittle glassy appearance usually follows a period of slow crack growth, denoted by fan shaped markings of local ductility, though still brittle overall. In this near brittle regime the fracture toughness is sensitive to strain rate so that high values of effective surface energy are easily induced by rapid testing or notch bluntness. At impact rates the toughness increases again. For design purposes, in the absence of environmental effects, the onset of slow cracking and rapid (glassy) fracture, can be associated with fracture toughness K1c of about 800 Ibf/in3/2 (90 kg/cm3/2) and 1600 Ibf/in3/2 (180 kg/cm3/2) respectively. Detailed studies have not been made on other materials but a guide to the levels of notch toughness and notch brittle temperatures are given for several plastics.
Application of time‐temperature superposition principle to long term engineering properties of plastic materials
Authors: Seitz J. T. , Balazs C. F. 
Published: December 2004

AbstractTime‐temperature equivalence was used to predict the long term engineering behavior of highly crystalline ethylene‐butene copolymers. The long term behavior (greater than 1000 hrs.) was accurately predicted from tests of short duration (30 hrs.). This time‐temperature principle was applied to stress‐relaxation and creep at stresses, strains and temperatures normally encountered in engineering practices. It was also used to solve a design problem involving the creep deformation of metal plastic laminates. Long term tests were performed to confirm the predicted results. This technique was not applicable to rubber modified polystyrene because of an unexpected transition at 88°F.
Deformation and aging of quenched polypropylene
Authors: Gezovich D. M. , Geil P. H. 
Published: December 2004

AbstractThe physical properties, i. e., yield stress and stress‐strain curve of the quenched (“smectic”) form of polypropylene have been shown to be time dependent at room temperature. The yield stress increases linearly with the logarithm of film age. No changes in the x‐ray diffraction pattern, infra‐red spectrum, electron diffraction pattern or morphology have been observed corresponding to this change in physical properties. A molecular mechanism is proposed which will explain this again process. Spherulites of the quenched form have been found to deform affinely when drawn. In contrast to this, slow cooled films show complete destruction of internal spherulite (lamellar) order, indicating a complex mechanism of deformation.
Prediction of melt viscosity flow curves at various temperatures for some olefin polymers and copolymers
Authors: Mendelson R. A. 
Published: December 2004

AbstractA knowledge of the variation of melt viscosity of thermoplastic polymers with both shear rate and temperature is of considerable importance to plastics engineers as well as to polymer rheologists. The actual measurement of melt viscosity at a large number of temperatures and shear rates is frequently a tedious and time‐consuming task. A technique has been developed, based upon the applicability of shear rate‐temperature superposition, for predicting the flow curves of a number of olefin polymers and copolymers at various temperatures from experimental data obtained at one temperature for the material in question. The experimental validity for superimposing log shear stress—log shear rate curves at different temperatures along the log shear rate axis has been established for both high and low density polyethylenes, polypropylene, polybutene‐1, and poly (ethylene vinyl acetate) copolymers. The temperature dependence of the resultant shift factors has been determined for each system, and the method of utilizing this information to predict viscosities as a function of temperature and shear rate is discussed.
Particle size measurement of the dispersed phase in rubber modified polystyrene
Authors: James D. E. 
Published: December 2004

AbstractA widely accepted method for determining the particle size of the dispersed phase in impact polystyrene is by the microscopic examination of microtomed sections or dilute solutions of the polymer. Although this technique is relatively quick, it has obvious shortcomings to its statistical relaibility. In an effort to obtain more meaningful data, a Coulter Counter was employed to measure the average particle size and particle size distribution of the dispersed phase in a number of impact polystyrene samples. The materials examined contained rubber particles ranging from one to twenty microns in diameter. It was found that the weight average distribution of these particles was most nearly described by a log‐normal probability function. The relative accuracy and reproducibility of the measurements made with the Coulter Counter suggest that it is a valuable tool for obtaining quantitative particle size information on the rubber modified polystyrene system.
Morphology of plastic/rubber blends
Authors: Ho R. M. , Wu C. H. , Su A. C. 
Published: December 2004

AbstractBlends of polypropylene (PP) and ethylene‐propylene rubber (EPR) and blends of polystyrene (PS) and styrene‐butadiene rubber (SBR) were prepared in a laboratory‐scale internal mixer at various blend compositions and rotor rates. Blend morphology was studied by means of electron microscopy. For each blend pair under the given processing conditions, the phase inversion process occurred progressively with respect to the variation in blend composition; it is within this composition range of phase inversion that dual‐phase continuity was observed. In addition, Characteristic torque values of blends were found to deviate negatively from a linear additivity rule; the composition range of maximum deviation from linear additivity corresponded approximately to the composition range where dual‐phase continuity was observed. Sperling's predictive scheme was found to yield acceptable (although not completely satisfactory) estimates for compositions of dual‐phase continuity in the present systems. It was also observed that partial cross‐linking of SBR during the mechanical blending process, as suggested by the appearance of a cure peak in the torque curve and supported by infrared spectroscopic evidence, resulted in morphological features drastically different from those of the uncured blends.
Characterization and processing of blends of polyethylene terephthalate with several liquid crystalline polymers
Authors: Sukhadia A. M. , Done D. , Baird D. G. 
Published: December 2004

AbstractBlends of an engineering thermoplastic, poly(ethylene terephthalate) (PET), and two liquid crystalline polymers (LCPs) viz., copolyesters of PET and parahydrox‐ybenzoic acid (PHB) in 40/60 mole percent (LCP60) and in 20/80 mole percent (LCP80) were prepared. A blend of LCP60 and LCP80 in 50/50 weight percent (LCP60‐80) was blended with PET. Both flat films and rods were extruded and their properties examined. The morphology of the films investigated using Scanning Electron Microscopy (SEM) revealed that the LCP phase remained as dispersed droplets in the PET matrix. In spite of the lack of fibrillation in these films, the mechanical properties were enhanced to some extent with a maximum at 10 weight percent of the LCP phase. However, in the case of the rods thin fibrils of the LCP phase of the order of 1 μm in diameter were observed provided the composition of the LCP was 20 weight percent or greater. This success In achieving fibrillation is through to be due to the extensional flow fields present at the entrance of the capillary die and the fact that a short L/D ratio die was used. Differential Scanning Calorimetry (DSC) thermograms of the extruded films indicated that the LCP phase may act as a nucleating agent for the crystallization of PET. Rheology of the blends revealed that the complex viscosity of the blends is not much different from that of pure PET. This is attributed to the partial miscibility of the two components. Based on the DSC results and residence times in the extruder, it is concluded that no significant transesterification reactions appear to have: taken place in the blends. The rheology is studied further with respect to the cooling behavior of the pure components and factors important to the fibrillation of the LCP phase and the formation of in‐situ reinforced composites are discussed.
Morphology and mechanical properties of thermoplastic composites containing a thermotropic liquid crystalline polymer
Authors: Crevecoeur G. , Groeninckx G. 
Published: December 2004

AbstractBlends of two thermotropic liquid crystalline polymers (TLCPs), with brittle and ductile matrix materials were both injection molded and spun into fibers, in order to investigate the mechanism of in‐situ mechanical reinforcement. In the injection molded samples, the TLCP was only moderately elongated into fibrils, and the mechanical properties were below predictions of the rule of mixtures. Fibers spun out of the blends contained numerous fine fibrils with nearly infinite aspect ratio, and as expected, the modulus increased linearly with the TLCP volume fraction, obeying the Tsai‐Halpin equation for transversely isotropic composites. Wide angle X‐ray diffraction measurements, as well as determination of the fiber‐moduli, revealed that during spinning not only a macroscopic elongation of the fibrils was achieved, but also a considerable molecular orientation within the TLCP domains.
Morphology‐processing relationships in polyethylene‐polyamide blends
Authors: Serpe G. , Jarrin J. , Dawans F. 
Published: December 2004

AbstractBlends of polyethylene (PE) and polyamide (PA) were prepared by a melt mixing process. The dependence of the number average size An of the dispersed phase on hydrodynamic conditions not only of shear rate but also temperature, inter‐facial tension, viscosity of the blends (WU's treatment), and dispersed phase concentration were studied. The analysis of PE‐PA blend morphology shows An to be the result of a balance between coalescence and disruption of the particles in the melt, and to display a strong increase in particle size when the minor component concentration is enhanced. These observations can be explained by a change in the rheology of the system. These assumptions are confirmed by the insertion in the blend of an ethylenemaleic anhydride (EMA) copolymer that yields EMA‐g‐PA graft copolymer during mechanical processing. Formation of this graft copolymer has been indicated by a strong particle size reduction and its concentration was measured by infrared experiments. The EMA‐g‐PA copolymer seems to decrease the blend interfacial tension and to deter the coalescence process.