bluuebunny/crossref_metadata_2025_split huggingface dataset:
Critical stress intensity factor of epoxy mortar
Authors: Dharmarajan N. , Vipulanandan C. 
Published: December 2004

AbstractFracture behavior of epoxy mortar was investigated in Mode I fracture using single edge notched beams with varying notch depth and beam thickness. The beams were loaded in both 3‐point and 4‐point bending. Influence of polymer content and temperature on the fracture behavior of epoxy mortar was studied using uniform Ottawa 20–30 sand. The polymer content was varied between 10 percent and 18 percent of the total weight of the composite. The temperature was varied between 22°C and 120°C. The flexural strength of the polymer mortar increases with increase in polymer content while the flexural modulus goes through a maximum. The critical stress intensity factor (KIC) was determined by several methods including compliance method (based on crack mouth opening displacement) and finite element analysis. TheKICfor epoxy mortar increases with increase in polymer content and epoxy mortar strength but decreases with increase in temperature. The critical stress intensity factor of epoxy mortar is represented in terms of polymer content and polymer strength or stiffness. Numerical tests based on random sampling and stratified sampling procedures were performed to substantiate the experimentally observed fracture toughness values of epoxy mortar.
Stored energy of cold work in polystyrene
Authors: Chang Benjamin Tai‐An , Li J. C. M. 
Published: December 2004

AbstractThe energy stored in polystyrene after plastic deformation is measured by the differential scanning calorimetry (DSC) technique. Similar to metals, the stored energy increases with plastic straining, first rapidly, and then more slowly, and finally the stored energy seems to approach a saturation value (about 1 cal/gram). By comparing to the plastic work done, the fraction stored ranges from 30 percent after 10 percent compression to 10 percent after 60 percent compression. The fraction is about twice as large as that of copper. The release of stored energy has two distinct parts, one below Tg and the other above Tg. Most of the strain recovery seems to accompany the second part. By using the Kissinger plot, the second part has an activation energy, of 142 kcal/mole which is about 10 percent larger than that of compressive strain recovery.
Physical aging of amorphous poly(etheretherketone) (PEEK)
Authors: Carfagna C. , Amendola E. , D'Amore A. , Nicolais L. 
Published: December 2004

AbstractThermal treatment of amorphous poly(aryl‐ether‐ether ketone) below the glass transition temperature has been studied. The extent of aging was measured by differential scanning calorimetry. X‐ray and Fourier transform infrared spectra were used to study both melt‐cast and annealed samples. The effect of the thermal treatment of viscoelastic response was evaluated using creep tests. Aging has been shown to be accompanied by a marked change in the transport properties of the material.
Analysis of the performance of cooling extruders in thermoplastic foam extrusion
Authors: Han Chang Dae 
Published: December 2004

AbstractThe performance of cooling extruders widely used in thermoplastic foam extrusion was analyzed, by numerically solving the equations of motion and heat transfer. Analysis of cooling extruders does not require a consideration of the melting behavior of polymers, thus simplifying the system equations considerably. The flow geometry analyzed was an unwound screw channel of a single‐screw extruder, i.e., a rectangular channel of uniform height followed by diverging and converging sections. Due to the cooling of both the extruder barrel and the screw, the heat transfer equation considered includes the terms describing the convective heat transfer in the down‐channel direction and the conductive heat transfer in the cross‐channel direction, in addition to the terms describing the viscous shear heating. For the analysis, a power‐law model was used as the constitutive rheologlcal equation, describing the viscosities of a mixture of a fluorocarbon blowing agent and a low‐density polyethylene melt (or polystyrene melt). The parameters in the Theological model were determined using the data of Han and Ma (13). In obtaining numerical solutions of the equations of motion, an integration method was employed to overcome the problem of numerical instabilities. The present analysis predicts the profiles of developing temperature and velocity in the down‐channel direction, and the profiles of temperature, velocity, shear rate, and viscosity in the cross‐channel direction. In presenting the results of computer simulation, emphasis is placed on the effects of cooling the extruder barrel and screw on the performance of cooling extruders, in terms of the pressure drops along the extruder axis and the mechanical power consumption. This study provides a rational basis for the design of cooling extruders widely used in thermoplastic foam extrusion and for the selection of optimum extrusion conditions in producing thermoplastic foams.
Time‐temperature superposition and physical aging in amorphous polymers
Authors: Matsumoto D. S. 
Published: December 2004

AbstractIn the past, time‐temperature superposition has been used to extend the time scale of creep tests in polymers from the short times easily obtained in the laboratory to long times seen in actual use. A fundamental assumption of time‐temperature superposition is, however, that the polymer does not change in structure as a function of time. Because ductile amorphous thermoplastics physically age below Tg, the structure of the polymer changes on a time scale comparable to the time duration of the creep test. Thus, the time‐temperature superposition prediction greatly exaggerates the amount of creep in amorphous thermoplastics. For samples aged at the test temperature for one hour before testing, the difference between the time‐temperature superposition prediction and the actual creep data after 10 days is greater than a factor of ten in time.
The effect of annealing at 135° on the mechanical properties of injection molded high density polyethylene‐polypropylene blends
Authors: Varin R. A. , Djokovic D. 
Published: December 2004

AbstractThe effect of annealing at 135°C for 5 hours on the tensile properties of mechanically mixed and then injection molded high density polyethylene (HDPE) and polypropylene (PP) blends has been investigated. Both the tangent elastic modulus and the tensile strength at yield exhibit a non‐linear behavior versus blend composition with a minimum of properties typical for incompatible blends. Annealing substantially improves mechanical properties of pure components and blends (20 percent increase in the yield strength of pure components and blends and the modulus of pure components, and ∼40 percent increase in the modulus of 50/50 blends) but the property behavior versus composition is still nonlinear. Scanning electron microscopy studies of fracture surfaces of blends seems to indicate some improvement in bonding between phases as a result of annealing, Both the elastic modulus and yield strength fit extremely well to the modified “rule of mixtures” equation in the general form: Mb = MPEφPE + MPPφPP + ΔMPE/PPφPEφPP where Mb is the blend property, MPE and MPP are properties of pure PE and PP components, φPE and φPP are weight fractions of PE and PP, and ΔMPE/PP is the interaction term being a measure of the deviation from simple additivity.
Mechanical properties of rigid thermoplastic foams—Part I: Experimental considerations
Authors: Stokes V. K. , Nimmer R. P. , Ysseldyke D. A. 
Published: December 2004

AbstractThe through‐thickness variation in the porosity of structural foam material is known to result in different “material properties” when mechanics based on homogeneous materials is used to interpret data from standard tensile and bend tests. Unresolved issues relating to structural design include the specification of the most useful test specimen, the identification of useful material properties, and the application of these properties to part design and analysis. This paper develops procedures for determining the mechanical properties of rigid thermoplastic structural foams, and for the application of these properties to the design of load‐bearing components. Rather than molded specimens, it is suggested that specimens cut from large, edge‐gated plates be used for determining mechanical properties of structural foams. By modeling foams as continuous but nonhomogeneous materials, it is shown that data from simple tensile and flexural tests can be used in structural analysis to systematically account for the through‐thickness variation of material properties.
Mechanical properties of rigid thermoplastic foams—Part II: Stiffness and strength data for modified polyphenylene oxide foams
Authors: Nimmer R. P. , Stokes V. K. , Ysseldyke D. A. 
Published: December 2004

AbstractThe through‐thickness variation in the porosity of structural foam material is known to result in different “material properties” when mechanics based on homogeneous materials is used to interpret data from standard tensile and bend tests. Procedures for determining the mechanical properties of rigid thermoplastic structural foams and for the application of these properties to the design of load‐bearing components were developed in a companion paper. This paper reports the mechanical properties of modified polyphenylene oxide foams, such as elastic moduli, ultimate stress and strain, as determined by tests on specimens cut from large, edge‐gated foam plates. Tests were conducted to study plate‐to‐plate variations in properties and to evaluate the effect of specimen thickness. Correlations of tensile and flexural data with the average specimen density are also discussed.
Dielectric properties of medium thermal black‐polyethylene systems
Authors: Yacubowicz J. , Narkis M. , Benguigui L. 
Published: December 2004

AbstractThe dielectric properties of thermoplastic and cross‐linked polyethylene compounds with a low structure medium thermal carbon black are described in the frequency range between 30 and 8000 kHz as a function of frequency, temperature, and carbon black loading. Very high values of the dielectric constant were obtained for the conductive samples. The systems investigated are shown to follow percolative type models with experimental critical exponents in good agreement with the predicted values. The dielectric constant increases slowly with the carbon black concentration up to roughly the percolation concentration, then increases rapidly, and subsequently decreases at the higher black loadings. The dissipation factor‐concentration curves show maximum values in the vicinity of the percolation concentration. The dielectric properties of these systems are discussed in terms of interfacial Maxwell‐Wagner polarization effects.
Dynamic mechanical behavior of copolymers containing carbon black
Authors: Gandhi K. , Salovey R. 
Published: December 2004

AbstractThe storage and loss moduli of random copolymers of styrene and butyl methacrylate containing carbon black of varied surface area were determined by dynamic mechanical analysis at several temperatures about 100°C above the glass‐transition temperature, Tg. At low frequencies, the pure polymers exhibit linear double log plots of moduli against frequency, with slopes of unity and approaching two for G″ and G′, respectively. With the addition of carbon black filler, both G′ and G″ become independent of frequency and temperature at low frequencies, consistent with yield behavior arid the formation of a carbon black network. The limiting dynamic complex modulus exceeds the yield stress from steady shear rheology, perhaps indicating the extent of the carbon black network, which was highest for low‐molecular‐weight copolymer and polystyrene. The filled random copolymers behaved Theologically like similarly filled polystyrenes of comparable molecular weights. Plasticization effects observed in the steady shear rheology of filled copolymers containing small concentrations of carbon black were not observed in dynamic mechanical analysis, although dynamic moduli converge at high frequency.
Service life of crosslinked polyethylene as high voltage cable insulation
Authors: Bernstein Bruce S. 
Published: December 2004

AbstractThis paper provides a summary of four EPRI‐sponsored contracts that studied the physico‐chemical characteristics and thermal and electrical behavior of unaged and service‐aged crosslinked polyethylene (XLPE)—insulated cables, and sections of the insulation obtained from this extruded cable. It has been demonstrated that volatile components generated primarily from the peroxideinduced crosslinking process can be defined and quantitatively measured. The morphology of the aged and unaged XLPE extruded insulation can be defined, and the thermal behavior on a micro (morphology changes) and macro (cable aging) level compared. Changes in microvoid level due to melting and recrystallization during cable operation appear to correlate with the limited amount of ac breakdown strength data obtained, and thermal overload of the cable conductor causes complete melting (and recrystallization on cooling) reducing the microvoid level. A single thermal overload alters the morphology but many thermal overloads are required to drive off the volatiles.
Influence of rubber content on static and dynamic properties of polystyrene
Authors: Sauer J. A. , Trent J. , Chen C. C. 
Published: December 2004

AbstractMechanical properties, deformation modes under both uniaxial tension and compression, low temperature mechanical relaxation behavior, and resistance to fracture under dynamic loading have been investigated for a medium impact grade of polystyrene, Shear yielding is the dominant mode of plastic deformation in compression while matrix crazing, together with some tearing and cavitation of the rubber phase, occurs in tension. The craze microstructure, as determined by transmission electron microscopy (TEM), is typical of that noted in polystyrene, with sharp craze‐bulk interfaces and a characteristic midrib section. The presence of a third phase, possibly a processing aid, is evident in the TEM scans and in the dynamic mechanical data. The present data, together with the data obtained on polystyrene and on high impact polystyrene, are used to show the strong influence of rubber content on various mechanical properties, such as the tensile craze yielding stress, ductility, compression yield strength, degree of strain softening, and fatigue durability.
A comparative study of structure‐property relationships in low‐profile polyester matrices
Authors: Lam Patrick W. K. 
Published: December 2004

AbstractStructure‐property relationships of polyester matrices containing various low profile additives such as poly(vinylacetate), polyurethane, poly(methyl methacrylate), polystyrene, and polycaprolactone were studied. The morphology and particle size of the dispersed phases in the polyester matrices are very dependent upon the type of low profile additives incorporated in the cured resins. Microvoids which are responsible for the degradation of physical properties of resin matrices are usually observed in the polyester phase and/or the dispersed phase of the low‐profile resin matrices. Low profile additives, in general, lower the glass transition temperatures of polyester matrices, slightly increase the loss moduli and the loss factors, and slightly decrease the storage moduli. These polymeric additives also degrade tensile properties and improve the fracture toughness of polyester matrices, but do not have significant effects on the thermal stability.
Polymer blend containing a thermotropic polyester with long flexible spacer in the main chain
Authors: Shin Boo Young , Chung In Jae 
Published: December 2004

AbstractPolymer blends of nylon 66 and thermotropic polyester with long flexible spacers in the main chains were prepared by melt mixing. The samples were made as single filaments by passing the polymer blend through a small and round die of a capillary rheometer. Mechanical properties of blends showed that the modulus and strength of nylon 66 could be improved without reduction of extensibility. The morphology of fractured surfaces was observed by a scanning electron microscope (SEM). It showed that the microfibrillar structure of a thermotropic polyester was formed by extensional flow while the spherical and ellipsoidal particles in the nylon 66 (matrix polymer) were produced by shear flow. The polyester particles were occasionally covered with adhering matrix polymer because of good adhesion between these two polymers. They were highly elongated by tensile stress without loss of elongational characteristics of blends. This fact was explained by very good adhesion between the two phases.
Polyester‐polystyrene block copolymers and their influence on phase morphology and mechanical properties in polymer blends
Authors: Yoshida M. , Ma J. J. , Min K. , White J. L. , Quirk R. P. 
Published: December 2004

AbstractNew block copolymers of polystyrene with polyesters have been synthesized and investigated as compatibilizing agents. The addition of block copolymers in immiscible blends of polybutylene terephthalate and (i) polystyrene, (ii) polystyrene/poly(2,6‐dimethyl 1,4‐phenylene oxide) as well as (iii) high impact polystyrene drastically reduced the dimensions of the dispersed phase and stabilized the phase growth with annealing time. Stress‐strain curves for the binary blends indicate brittle behavior. The addition of more than 10 wt% of block copolymers transforms their brittle characteristics to ductile behavior.
Observation of carbon black agglomerate dispersion in simple shear flows
Authors: Rwei S. P. , Manas‐Zloczower I. , Feke D. L. 
Published: December 2004

AbstractExperiments aimed at studying the mechanisms of agglomerate breakup due to the application of a simple shear flow field were performed in a cone and plate transparent device. Spherical compacts of carbon black (diameters 1‐2 mm) in a range of different porosites were used in the experiments. Two distinct breakup mechanisms, denoted as “rupture” and “erosion”, were observed. The critical stress for erosion was found to be smaller than that for rupture. Once erosion starts, it continues for very long times. Rupture occurs shortly after reaching a critical stress and concludes abruptly. For this analysis of rupture, the dimen‐sionless group \documentclass{article}\pagestyle{empty}\begin{document}$\alpha {\rm = \{ }\eta {\rm .}\mathop \gamma \limits^{\rm .} {\rm /K'}\phi ^{\rm 4} {\rm \} }$\end{document}, which is the ratio of applied stress to cohesive strength, was found to be a significant parameter for determining the final particle size distribution. The size analysis of fragments produced by shearing pellets for 1 minute showed a lognormal distribution function.
Yield behavior of polypropylene filled with CaC03 and Mg(OH)2. I: “Zero” interfacial adhesion
Authors: Jančář Josef , Kučera Jaroslav 
Published: December 2004

AbstractThe composition dependence of tensile yield stress (σyc), and the effects of filler particle shape and surface treatment were investigated for polypropylene (PP) filled with CaCO3 or with Mg(OH)2. Poor adhesion between PP and CaCO3 accounted for a decrease of σyc with increasing σf. In spite of the poor adhesion between PP and Mg(OH)2, σyc either slowly decreased with increasing Vf or remained constant up to Vf = 0.25. Surface treatment of the fillers facilitated better dispersion in PP. On the other hand, σyc was reduced due to the lower thermodynamic work of adhesion (WA). The semiempirical one‐parameter equation proposed by Turczanyi, Pukanszky, and Tüdüs (TPT) was considered plausible and was employed in the study of the effects of matrix‐filler interaction.
Effect of strain rate and temperature on the performance of epoxy mortar
Authors: Vipulanandan C. , Mebarkia S. 
Published: December 2004

AbstractThe behavior of epoxy mortar was studied under various curing conditions, temperature and strain rate. The effect of aggregate size and distribution on the mechanical properties of epoxy mortar was also studied. Epoxy mortar with a uniform fine sand was cured at various temperatures to determine the optimum curing condition. The strain rate was varied between 0.01 to 6 percent strain per minute and the testing temperature between 22°C and 80°C. The strength, modulus, and compressive strain‐strain relationship of polymer mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of epoxy mortar are quantified. Compared to the uniformly graded fine aggregate fillers the gap‐graded aggregates produced polymer mortar with better mechanical properties. The compressive modulus and splitting tensile strength of epoxy mortar are related to their compressive strength. A new nonlinear constitutive model is proposed to predict the complete compressive stress‐strain behavior of epoxy mortar. The constitutive relationship parameters are also related to the testing temperature and logarithmic strain rate.
Relationships in a bismaleimide resin system. Part II: Thermomechanical properties
Authors: Donnellan Thomas M. , Roylance David 
Published: December 2004

AbstractA range of bismaleimide resins of differing network structure was produced both by varying the ratios of N,N′‐bismaleimido‐4,4′‐diphenylmethane (BMI) and methylene dianiline (MDA), and also by the use of different thermal processing cycles. Characterization of the resins by a variety of mechanical, physical, and micrographic techniques showed that properties such as modulus and yield strength varied directly with crosslink density and its associated free volume. Fracture toughness was found to increase as the crosslink density decreased, and microscopic investigation of the resin fracture surfaces identified characteristics which correlated with the resin fracture toughness.
Study of suspension polymerization of styrene with a circular loop reactor
Authors: Hosogai Kazuhiko , Tanaka Masato 
Published: December 2004

AbstractA circular loop reactor was devised and used to study the suspension polymerization of styrene. The transient droplet diameter distributions and the final particle size distributions were measured by changing the impeller diameter and the impeller speed. The effects of the impeller diameter on the size distributions and mean sizes of the final polymer particles were investigated. In the case of lower mixing power, the mean polymer droplet diameters depend upon impeller diameter in the early stage of polymerization, but become almost identical irrespective of the impeller diameter after the middle stage. In the case of higher mixing power, the mean polymer droplet diameters are almost identical irrespective of the impeller diameter throughout polymerization. The final mean particle sizes are correlated only with mixing power.
Non‐Isothermal crystallization of isotactic polypropylene in dotriacontane. I: Effects of dilution, cooling rate, and nucleating agent addition on overall crystallization kinetics
Authors: Lim Gordon B. A. , Lloyd Douglas R. 
Published: December 2004

AbstractThe overall non‐isothermal crystallization kinetics for nucleated and non‐nucleated isotactic polypropylene (iPP) in dotriacontane systems was investigated. Adipic acid was used as the nucleating agent. Crystallization peak temperature was determined via differential scanning calorimetry as a function of the experimentally controlled variables iPP concentration, cooling rate, and nucleating agent concentration. The influence of these variables on crystallization mechanism and spherulitic structure as implied by the Ozawa and Ziabicki analyses was determined. The non‐isothermal crystallization kinetics presented here are the first for iPP‐diluent systems with and without nucleating agent.