bluuebunny/crossref_metadata_2025 huggingface dataset:
A new apparatus to measure the thermal conductivity and diffusivity of thermoplastic and thermosetting polymers
Authors: Sourour S. , Kamal Musa R.
Published: December 2004

A new apparatus has been constructed to measure the thermal conductivity and the thermal diffusivity of reactive and nonreactive liquids and solids. The method used consists in suddenly subjecting the test specimen to a thermal flux and measuring the velocity of the heat wave across the sample. Maintaining the heat flux leads to a steady thermal gradient across the sample from which the thermal conductivity can be determined. The test duration is short relative to durations employed by existing conventional techniques and thus causes only a small thermal disturbance to the sample of the order of 1 to 2°C. Thermal properties of liquids and solids, including thermoplastics and a typical epoxy resin during cure with different equivalents of an aromatic diamine hardener have been measured near room temperature. Experimental data compare favorably with literature values for similar systems. Variations in thermal conductivity and diffusivity during cure have been obtained through a series of individual discrete measurements to cover the whole isothermal cure history. The results have been analyzed and discussed with respect to the cure characteristics of the resin and the nature of the physicochemical changes the material undergoes during cure.
Jetting phenomena in injection mold filling mold filling
Authors: Oda Kunio , White James L. , Clark Edward S.
Published: December 2004

Experimental studies of injection molding of polymer melts have classified two regimes of mold filling–simple filling and jetting. In this paper we have examined a wide range of polymer melts and mold designs in an attempt to devise a criterion for the transition between these regimes. This criterion is found to be related to the extrudate swell d, gate diameter D, and small cavity dimension at the gate h. For isothermal mold filling, if d/h exceeds 1.0, the‐melt will contact the mold, stick to it, and induce a simple mold filling regime. The variation in behavior in vertical and horizontal mold filling is considered, as is the influence of barriers near the gate. For the non‐isothermal mold case, the manner of filling is similar, and the criterion for jetting remains the same, The die swell behavior in the non‐isothermal case is complex.
Stress measurement in polymeric materials by X‐ray diffraction
Authors: Barrett Charles S. , Predecki Paul
Published: December 2004

Experiments are described which show that stresses in amorphous polymers can be measured by diffracting X‐rays at high Bragg angles from a filler consisting of crystalline particle or powders. The method is applicable, when calibrated, to both applied and residual stresses, to stress relaxation studies, to both tensile and compressive stresses, to both interior and surface positions in an object, and to composites of various types as well as to polymers that are substantially homogeneous. In the lower (Hookian) range, strains and stresses in metallic embedded particles increase linearly with applied stresses and strains in the matrix. When applied stresses exceed an apparent yield point, which correlates with the yield strength of the metallic filler, the elastic strains in the particles increase only slightly or even decrease as the matrix strains are increased, and with constant applied strain, the particles reveal changes due to relaxation. Strains in the particles are found to be smaller, and stresses higher, than in the matrix. Tests of graphite‐fiber epoxy composites with embedded filings of silver or aluminum alloy show that compressive residual stresses from curing at 350°C and cooling to room temperature are registered in the particles as well as stresses externally applied to the cured composite. Precision of the order of 1000 psi (0.7 kg/mm2 or 6.9 M Pa) was obtained with measurements made and evaluated rapidly and simply; with more refined techniques, much higher precision would be possible.
Increase of adhesive bond strength through the mechanochemical creation of free radicals Part II. Shear and peel test results
Authors: Lerchenthal Ch. H. , Brenman M.
Published: December 2004

The Part I paper described the mechanochemical basis for achieving high adhesive strength in bonds between polymeric surfaces such as polyethylene, polypropylene, and Teflon, using the SABRA method (Surface Activation Beneath Reactive Adhesives). This paper gives a brief survey of bonding techniques as well as results of shear tests of simple lap joints and scarfed tube joints. They compared favorably with other methods such as CASING, Peeling test results are also presented. Mixed systems were examined such as glass fiber reinforced polyester bonded to polypropylene and aluminum with thin films of polymeric material sandwiched between. A start was made towards of optimization and exploration of primer specificity for different materials, The implications and further applications of the SABRA method are discussed.
Influence of long‐chain branching on the viscoelastic properties of low‐density polyethylenes
Authors: Wild L. , Ranganath R. , Knobeloch D. C.
Published: December 2004

Melt How data has been determined for a series of fractionated and whole low density polyethylenes which has been characterized in terms of their molecular weights and degree of long‐chain branching, (LCB). The resulting data indicate that low LCB influences melt flow both through a reduction in molecular size and an increased level of intermolecular interaction. Die swell measurements on whole polymers indicate an increase in melt elasticity with increase in degree of LCB for samples of similar melt flow (MI). Comparison of GPC data with observed die swell characteristics indicates that die swell is a molecular size dependent property and independent of intermolecular entanglement effects, suggesting that the measurement of elastic properties of LDPE melts will provide a means of determining relative degrees of LCB for commercial resins.
Extrusion of polymer tubing using a rotating mandrel
Authors: Shepherd G. W. , Clark H. G. , Pearsall G. W.
Published: December 2004

A rotating mandrel in a tubing die produces multiaxial orientation in the extruded melt. If the polymer melt is quenched rapidly, some multiaxial orientation is retained in the resultant tubing. Multiaxially oriented tubing exhibits reduced crack propagation and some enhancement of yield and fracture strengths. During the processing of multiaxially oriented tubing, relaxation occurs after the melt leaves the die and gives rise to wall thickening and reduction in the lumen of the tubing; the magnitude of these effects is a function of the rate of mandrel rotation.
A forced torsional oscillator for dynamic mechanical measurements
Authors: Davis William M. , Macosko Christopher W.
Published: December 2004

A forced torsional oscillator (FTO) for measuring dynamic properties from 0.01 to 30 Hz and −190 to +250°C is described. It uses a digital transfer function analyzer to determine G′ and G″ directly. Errors such as clamping corrections, phase angle resolution, and instrument phase shift are evaluated. FTO measurements vs temperature on polymethylmethacrylate (PMMA) and polycarbonate compare well with free torsion pendulum data. Measurements on a silicone liquid vs frequency compare well to eccentric rotating disks data. The frequency sensitivity of the dynamic mechanical response of PMMA and polycarbonate is evaluated at 0.1, 1 and 10 Hz. The frequency dependence of the transitions is fit to an Arrhenius relation and activation energies calculated. A dimensionless transition temperature shift, ΔT*, giving the shift for a one decade frequency change divided by the temperature, is found to be approximately 0.01 for the glass transition and 0.07 for several secondary transitions in glassy polymers.
Liquid injection molding I. An investigation of impingement mixing
Authors: Malguarnera Salvatore C. , Suh Nam P.
Published: December 2004

The fluid mechanics of impingement mixing was investigated experimentally, and the design procedure, including scale‐up, for the MIT Liquid Injection Molding System was established. For impingement mixing to be effective, the Reynolds number based on the nozzle diameter must be greater than about 50 and the momentum ratio of the fluid components must he equal to 1 in addition to satisfying the desired mass flow rate ratio.
Liquid injection molding II. Mechanical design and characterization of a RIM machine
Authors: Malguarnera Salvatore C. , Suh Nam P.
Published: December 2004

A unique liquid injection molding machine for polyurethane was designed and built to process a large quantity of polyurethane in a short period of time. This machine has a continuously variable flow rate. Using inexpensive, low capacity gear pumps, 5 gallon hydraulic accumulators were charged with fluid components. The fluid can be pumped into the accumulators at low pressure followed by nitrogen gas addition to the bladders to raise the fluid pressure, or the charging pumps can pump up the accumulators against an existing pressure. The two components were then discharged under pressure through linkage activated ball valves and mixed together in a mixing chamber. The system provided for a very low pressure loss during discharge, resulting in high fluid velocity. Extremely high flow rates were possible: approximately 1440 lb/min at 2500 psi, a pressure less than the maximum possible system pressure. This system delivers large flow rates of high quality urethane while still maintaining its simplicity, light weight, and relative low cost.
The effect of polymer host on volume phase holographic recording properties
Authors: Bloom Allen , Bartolini R. A. , Hung P. L. K.
Published: December 2004

We have studied the effect of unsaturated‐polyester and epoxy hosts on the volume phase holographic recording properties of media using camphorquinone and 2, 3‐pentanedione as guests. The sensitivity, determined by holographic diffraction efficiency on exposure to an Ar+ laser, was used as a probe for the chemical behavior of the medium. Intramolecular, photochemical reactions involving 2, 3‐pentanedione in the epoxy hosts are less effective than in the polyesters. For inter‐molecular reactions initiated by photoexcited camphorquinone, media having polyester hosts are again more sensitive. The availability in unsaturated‐polyester hosts of residual monomer for free‐radical addition reactions is a determining factor in the recording mechanism.
Polyimides in lithography
Authors: Agnihotri R. K.
Published: December 2004

Polyimides and Polyamide‐imides have a high thermal and dimensional stability, good properties, and resistance to attack by solvents. These features, along with their electrical properties, have led to their wide acceptance in the electronics industry. Specifically, Polyimide masks are superior to conventional resists during metal deposition, sputter etching, and chip soldering, for which high‐temperature stability is essential. Such a mask is prepared by selectively etching the polyamide‐imide with in organic solvent such as ethylenediamine. The reaction of ethylenediamine with polyamide‐imides has been applied successfully in metallizing semiconductors by the lift‐off method; also, polyamide‐imides have been used as a reworkable protective coating for semiconductor modules.
Morphology and organizational characteristics of poly(m‐phenylene isophthalamide‐b‐ethylene oxide) systems
Authors: Fellers J. F. , Lee Yu‐Der , Zdrahala R. J. , Horne S. C.
Published: December 2004

A series of essentially triblock poly(m‐phenylene isophthalamide‐b‐ethylene oxide) with sequence PEO‐(MPD‐I)‐PEO or (MPD‐I)‐PEO‐(MPD‐I) and their admixtures with (PEO)n were studied as solution cast films. Experimental techniques included transmission optical microscopy, transmission electron microscopy, electron diffraction, and X‐ray diffraction. Characterization of these systems showed that structure could develop in two ways. The first way was the development of a typical polycrystalline structure of the (MPD‐I) segment by the action of such agents as formic acid. In a second manner, however, a non‐typical development was manifested by the appearance of crosses In the polarized opticial microscope. These samples showed only an amorphous halo when subjected to wide angle X‐ray diffraction measuremfents. Their small angle pattern suggested scattering by dispersed particles. Other experiments indicated the crosses would form only under an unusually restrictive set of conditions, principally that the PEO present must be above a certain molecular weight and concentration and, furthermore, that the solvent must contain a salt such as LiCl. These observations led us to speculate that optical activity of the films showing crosses could occur either by chain orientation near the interface of a spherical particulate second phase or from stress induced bond polarization resulting from the film formation process.
Morphology and properties of crystalline polyester‐siloxane block copolymers
Authors: O'Malley James J. , Stauffer Walter J.
Published: December 2004

A new series of crystalline (AB)n type multiblock copolymers based on crystalline poly(hexamethylene sebacate) (HMS) and amorphous poly(dimethylsiloxane) (DMS) has been prepared, and their solid state properties have been examined. The copolymers range from 0‐69 wt percent DMS, and they crystallize in spherulitic textures when cast in films from solution or the melt. As the DMS concentration in the copolymers increases, the spherulite sizes decrease, but only a very small melting point depression is observed. Available evidence suggests extensive microphase separation in the bulk of the solid state. Surface characterization of the copolymers indicates that phase separation is also prevalent at the polymer‐air interface. The block copolymers and polyblends have critical surface tensions of wetting very similar to DMS homopolymer.
New block copolymers of α‐amino acids
Authors: Uralil F. , Hayashi T. , Anderson J. M. , Hiltner A.
Published: December 2004

Triblock cepolypeptides of γ‐benzyl‐L‐glutamate and L‐leucine or L‐valine of high molecular weight have been prepared. The solid state structure of the block copolymers cast from preferential solvents has been compared with that of random copolymers of similar composition as well as the appropriate homopolymers. Infrared and solid state circular dichroism measurements indicate that the γ‐benzyl‐L‐glutamate and L‐leucine blocks assume an α‐helical conformation and L‐valine blocks a β‐sheet structure. The WAXD patterns of the block copolymers show overlapping reflections characteristic of the individual homopolymers. Further evidence for a phase separated morphology is provided by dynamic mechanical spectroscopy.
Unit cell deformation under elongational stress of oriented SIS three‐block copolymers
Authors: Manthis A. , Hadziioannou G. , Skoulios A.
Published: December 2004

A 50, 000 molecular weight SIS three‐block copolymer, containing 30 percent by weight of polystyrene and, presenting the cylindrical morphology, has been oriented by a novel shearing process at high temperature. The orientation has been studied by low‐angle X‐ray diffraction; the intensity of the (100) reflexion of the hexagonal array has been measured as a function of the angular position of the sample with respect to the direct beam. The samples have been found to be very similar to single crystals; not only the axes of the cylinders lie parallel to the shearing direction, but also the (100) lattice‐planes keep the same orientation in space throughout the whole volume of the specimen. Special probes for the mechanical tests have then been cut in the oriented material, parallel and perpendicular to the axis of the cylinders. The deformation under elongational stress of the external shape of the probes has been studied with a traveling microscope; when the cylinders are oriented perpendicular to the stress, the sample deforms elastically, the, size of the probe corresponding to the length of the cylinders remaining constant up to 200 percent deformation. Low‐angle X‐ray diffraction has been used to study the structural deformation under the same elongational stress; with the stress perpendicular to the cylinders, the unit cell seems to deform in an.affine way with respect to the macroscopic aspect; with the stress parallel to the cylinders, the structure is destroyed rapidly.
Domain‐boundary structure of styrene‐isoprene block copolymer films cast from solutions. III. Preliminary results on spherical microdomains
Authors: Todo Akira , Hiroyukiuno  , Miyoshi Katsunori , Hashimoto Takeji , Hiromichikawai
Published: December 2004

The microdomain structure of styrene‐isoprene A‐B type block copolymers having a nearly constant fraction of polyisoprene block segments (13 ∼ 22 wt percent) was investigated by small‐angle X‐ray scattering (SAXS) as a function of the molecular weights of the copolymers. The styrene‐rich block copolymers all have spherical microdomains of polyisoprene block segments dispersed in a matrix of polystyrene block segments. The size of the spherical domains increases with increasing molecular weight of the polyisoprene segment with a power of ca. 0.6. The thickness of the domain‐boundary interphase arising from a partial mixing of the incompatible segments at the domain‐boundary interface is also estimated by analyzing a systematic deviation of the SAXS intensity distribution from Porod's law at large scattering angles on the basis of the infinite slit‐height approximation. The results indicate the interfacial thickness to be about 20Å and to be almost independent of the molecular weight of the block copolymers studied. The applicability of the infinite‐slit height approximation in the analysis of SAXS intensity distributions at large scattering angles is also discussed in an approximate fashion.
ESR studies of polymer transitions. IV. Spin‐probe studies of styrene block copolymers
Authors: Kumler Philip L. , Keinath Steven E. , Boyer Raymond F.
Published: December 2004

ESR spin‐probe values of glass temperatures are reported for a series of di‐, tri‐, and radial block copolymers. With one exception, in which the hard phase is poly(t‐butylstyrene), the hard component is polystyrene (PS); the soft components include polybutadiene (PBD), polyisoprene (PI), hydrogenated PBD, hydrogenated PI, and poly(dimethyl siloxane) (PDMS). Tg's of the soft phase are in general agreement with those of the respective high molecular weight homopolymers; Tg's of the hard phase generally deviate widely from those of corresponding high molecular weight homopolymers. This deviation is interpreted in teens of a number of factors, including, the molecular weight of the hard phase, differences in solubility parameters for the two phases, percent of the hard phase present, and the presence of crystallinity. Comparison of Tg's determined by ESR with Tg's from dynamic mechanical methods on S‐B‐S triblocks of similar composition demonstrates that the ESR method is measuring the Tg of the interpliase and hence, in principle, its composition.
Micelle formation by butadiene‐styrene block polymers in n‐alkanes
Authors: Stacy C. J. , Kraus Gerard
Published: December 2004

Butadiene‐styrene block copolymers form micelles in selective solvents. Micelles of several BS diblock and BSB triblock polymers varying in composition and block length were investigated in n‐hexane, n‐heptane, and n‐decane using light scattering and sedimentation velocity, thus permitting characterization of both the micellar weight and abundance of micellar material. Depending upon polymer structure, solvent, concentration and temperature, solutions can be molecular, wholly micellar or a discrete mixture of both. The dominant structural variable is the length or molecular weight (Ms) of the polystyrene block. For Ms < 10, 000, solutions tend to be molecular; for Ms > 20, 000, they are essentially all micellar, with mixtures occurring at intermediate Ms. At any given Ms, increasing length of the polybutadiene block tends to solubilize the polymer. The mean number of molecules per micelle (n) depends upon whether the micelles are formed by direct dispersion of the polymer in the solvent at ambient temperature or whether they are formed from a true solution upon cooling. In the first instance, n rises rapidly with Ms; in the second, it is nearly independent of Ms. Blending of micellar solutions results in complex behavior with rearrangements to new micelles governed primarily by the thermal history of the solutions.
Bisphenol‐A‐polycarbonate‐bisphenol‐A‐polysulfone block copolymers
Authors: McGrath James E. , Ward Thomas C. , Shchori Ehud , Wnuk Andrew J.
Published: December 2004

Multiblock , block copolymers of bisphenol‐A‐polycarbon ate and bisphenol‐A‐polysulfone were prepared by three different synthesis routes. The in situ method consisted of forming the polycarbonate block in the presence of hydroxyl terminated polysulfone oligorner. The coupled oligomer technique utilized phosgene to link up the two preformed oligomers to high molecular weight. In one case, a perfectly alternating block copolymer was formed by reacting a ∼9, 000 Mn chloroformate terminated polycarbonate with a ∼9, 000 Mn hydroxyl terminated polysulfone. Block sizes from ∼4, 000 to ∼26, 000 were investigated. The oligomers and copolymers were characterized by potentiometric titrations and UV end group analysis. Membrane osmometry and gel permeation chromatography were also employed. Dynamic mechanical behavior of solvent cast and compression molded films was assessed via rheovibron measurements. The copolymers were ductile and transparent and displayed essentially only a single intermediate glass transition temperature, that is, microphase separation was not observed. This is in contrast to simple physical blends of the homopolymers or oligomers, which are opaque and display two glass transition temperatures.
Stratified two‐phase flog of molten polymers in circular dies
Authors: Uhland E.
Published: December 2004

A theoretical study has been carried out on the steady, axisymmetric two‐phase flow of molten polymers in circular dies. For both fluids, the shear rate dependence of the viscosity is described by a power law and the temperature dependence by an exponential function. Taking into account viscous dissipation, a numerical program has been developed to predict the radial position of the interface between the two fluids, the developing temperature and velocity fields, the shear rates, the shear stresses, the pressure drop as well as the field of shear deformation and the residence time distribution for different thermal boundary conditions. The numerical program is applied to the flow of a high‐viscous polymer melt, (high density polyethylene), surrounded by a small annulus of less viscous polymer ni lt, (low density polyethylene). Computed results are shown graphically.
Thereto‐oxidative degradation of polyethylene. IV. Blends containing poly(vinyl chloride) and chlorinated polyethylene as models for polyethylene recycle qualities
Authors: Holmström Arne , Sörvik Erling M.
Published: December 2004

In order to study the changes in mechanical and structural properties of low density polyethylene (LDPE) during recycling of PE film wastes from industrial and commercial sources, mixtures of LDPE with 5 percent poly(vinyl chloride) PVC were processed, recycled and heated in air. The effect of added chlorinated high‐density polyethylene (CPE), carbon black, antioxidants and heat stabilizers were also investigated. Compounding and recycling were performed in a twin screw extruder equipped with granulating device. Films were blown in an adiabatic vertical extruder. The thermo–oxidative treatments were carried out in a forced‐air oven at 107°C. Tensile strength, elongation to break and film impact strength were determined according to ASTM standards. Structural changes were determined by gel chromatography, solution viscometry, melt indexing, differential scanning calorimetry and infrared spectroscopy. Even 5 percent PVC adversely affects the proeessability and mechanical properties of LDPE films. Addition, of the same amount of CPE gives marginal improvements in the mechanical properties, possibly due to a compatibilizing action. PVC and CPE also adversely affect the thermooxidative stability of LDPE. When unstabilized, PVC and CPE evolve large amounts of HCl during processing. Minor degradation of the LDPE also occurs. Stabilization of the LDPE may be achieved by phenolic antioxidants.
Rubber heat engines, analyses and theory
Authors: Farris Richard J.
Published: December 2004

It has long been known that elastomeric solids could be used as the working “fluid” in engines designed to convert heat into mechanical work. In the past rubber heat engine cycles were not given serious consideration since energy alternatives were not in demand and a majority of the scientific community is unaware of their gas‐like thermodynamic behavior. Consequently, past work has dealt with the subject primarily as a novelty or as a demonstrative proof of thermodynamic behavior. This paper provides an idealized mechanical and thermodynamic analysis of the rubber cycle and compares it to an equivalent cycle wherein a gas is the working fluid. Experimental data on a small rubber fiber engine is included which confirms the high power potential of these engines when they are designed using modern elastomeric fibers. These materials have remarkable properties and can respond rapidly to cyclic thermal disturbances. Power densities of roughly one watt/g of rubber have been attained using only a 30°C difference between the heat source and heat sink. Engine speeds well over 1000 RPM have also been attained when atmospheric pressure steam was used as the heat source. The analyses demonstrate that elastomers are ideally suited for energy conversion when only small temperature differences are available.
Pressure‐specific volume‐temperature behavior of thermoplastics under normal processing conditions
Authors: Menges G. , Thienel P.
Published: December 2004

In the processing of thermoplastics, the economy of the process and the quality of moldings are decisively influenced by material thermal properties. Therefore, it is particularly important for the processor to know and consider such properties. Process analyses have revealed that the processing conditions can be set to achieve optimum results by the application of pressure‐volume‐temperature diagrams, particularly if used in conjunction with computer control of the process. A new measuring instrument is described which makes it possible to determine such diagrams under normal processing conditions, that is, at normal cooling rates and pressures. The results contrast with values heretofore quoted in the literature, where values have been measured at very slow heating and cooling rates. Some experimental results and their practical use are discussed.
Correlation of low density polyethylene rheological measurements, with optical and processing properties
Authors: Shida R. N. , Cancio L. V.
Published: December 2004

The processing properties of low density polyethylene melts, such as drawdown and neck‐in, and the final product properties, such as film haze and gloss, have been successfully correlated with rheological functions and the level of longchain branching. The rheological functions employed are the entrance pressure drop ΔPo and the swell ratio So, determined at a specified shear stress using aft‐orifice with a length/ diameter (L/D) ratio of zero. The calculation of shear stress requires additional measurements using adie with a finite L/D e.g. 20. The rheological functions ΔPo, and So are governed by the level of high molecular weight species and/or the level of long‐chain branching(LCB). If determined at a constant shear stress, in order to eliminate the effect of viscosity, they are a relative measure of elasticity. Higher ΔP0 and So indicate a higher level of LCB and correlate with poorer optical properties and drawdown in films.
Conductive polymeric compositions
Authors: Bigg Battelle Donald M.
Published: December 2004

In most low‐strength applications, plastics offer cost, maintenance, and density advantages over metals. Major deficiencies of plastics, however, are low thermal and electrical conductivities. Various studies have dealt with these problems, and it has been found that thermal conductivity and electrical conductivity can both be increased by the addition of conductive fillers to the polymer. The two parameters that most significantly affect the increase in conductivity of the resulting composite are volume loading of filler and filler shape. Fibrous conductors improve conductivity much‐more significantly than spheres, flakes, or irregular particulates. The effect of fillers on thermal and electrical conductivities is not the same. The maximum increase in thermal conductivity that can reasonably be expected over the base polymer is 100:1. Electrical conductivity, on the other hand, can be increased by a factor of 1015. One particularly attractive technique for increasing the electrical conductivity of polymers is electroless plating of metals onto glass fibers which are then incorporated into the polymer. Such a composite can he made electrically conductive with as little as 6 volume percent metal.
Stress cracking of plastics by gasoline and gasoline components
Authors: Wyzgoski M. G. , Jacques C. H. M.
Published: December 2004

The susceptibility of polycarbonate, polymethyl methacrylate, and cellulose acetate butyrate to gasoline‐induced stress cracking was evaluated by measuring the critical strains of specimens exposed to a variety of commercial gasolines and gasoline components. Cellulose acetate butyrate exhibited the greatest resistance to gasoline followed by polymethyl methacrylate and polycarbonate. Stress cracking was a complex function of gasoline composition. Measured critical strains generally decreased and the severity of cracking of molded parts generally increased as the total aromatic content of the gasolines increased. However, a significant difference in critical strains was observed between the individual aliphatic components of gasoline. No correlation was observed between critical strain and gasoline type, i.e., premium, regular, or unleaded. The effect of time of exposure was examined, and it was observed that for some binary mixtures splashing caused much more severe cracking than continuous exposure.
Effect of concentration on apparent viscosity of a globular protein solution
Authors: Pradipasena Pasawadee , Rha Chokyun
Published: December 2004

The viscosity of a globular protein solution as a function of concentration was studied with a cone and plate viscometef (Ferranti‐Shirley Viscometer System) using, β‐lactoglobulin as a model. An aqueous buffer solution (pH 7, ionic strength 0.04) containing up to 40 percent protein was subjected to rates of shear between 800 and 17,000 sec−1. Specific viscosity of β‐lactoglobulin up to 10 weight percent was proportional to the weight concentration of protein in solution such that: ηs = η0 [ 1+0.8 (weight percent concentration)] where η0 and ηs are viscosity coefficients for the pure solvent and the solution, respectively. For 3‐40 weight percent, a linear relation of shear rate and shear stress was observed at high shear rates. Linearity began at 3500, 4300, 6800, and 7000 see−1 for 10, 20, 30 and 40 weight percent concentrations respectively. The apparent viscosity was lower below these critical shear rates.
The mechanisms of elevated temperature property losses in high performance structural epoxy resin matrix materials after exposures to high humidity environments
Authors: Browning Charles E.
Published: December 2004

Absorbed moisture was found to plasticize the type of cross‐linked epoxy resin system investigated, causing a lowering of the Ta and in turn affecting mechanical response, such as by shifting the relaxation moduli to shorter times. The phenomenon is described and quantified in terms of an existing free volume theory relationship. Weight gains greater than equilibrium amounts were observed without accompanyingTgchanges which is attributed to moisture entrapment during microcracking in the resin. Creep studies performed under water at 300° F established an additional mechanism for loss of elevated temperature properties which is characterized by the appearance and growth of cracks in the material. The observed failure processes are described in terms of an existing theory for rupture of cross‐linked rubbers. The process is governed by the synergistic effects of moisture, temperature, and stress. Moisture changes the viscoelastic response of the material so that stress‐induced crack formation and growth is facilitated.
On the damage energy of polymers in creep
Authors: Brüller O. S.
Published: December 2004

Creep experiments carried out on transparent and translucent polymers permit the observation of irreversible material damage in the form of crazes or microcracks. The formation of such damage is strongly dependent on the applied stress, temperature and environmental conditions. The first appearance of observable material damage seems to be explicable by an energy criterion. The energy supplied by the external load can be divided into conserved and dissipated parts, each of them causing volume (isotropic) and shape (deviatoric) changes. The different parts of the energy can be computed if the creep‐compliance is approximated by a Prony‐Dirichlet series with a finite number of terms. Computations carried out for experiments with air as the environmental medium under isothermal conditions show the dependence between the appearance of first visible material damage (crazes or microcracks) and the conserved energy.
Oriented short glass‐fiber composites. IV. Dependence of mechanical properties on the distribution of fiber orientations
Authors: Kacir L. , Ishai O. , Narkis M.
Published: December 2004

Short glass fiber‐epoxy laminates of controlled fiber orientation and distribution were loaded to failure under uniaxial tension. The mechanical characteristics of specimens with different orientation patterns, which were determined experimentally, were compared with analytical predictions based on “Laminate Analogy” methods. Results show good agreement between empirical data and prediction in the case of stiffness, stress‐strain relationship and strength based on ultimate strain criteria. A methodology is proposed according to which a well‐defined, orthotropic, short fiber reinforced plastic system can be prepared, analyzed, and optimized by tailoring it according to the loading pattern in a similar manner to that of the well‐established, continuous fiber reinforced laminates.
The use of urethane rubber/epoxide resin blends as matrix materials for glass and carbon fiber composites
Authors: Wells H. , Hancox N. L.
Published: December 2004

We consider the effects of using urethane rubber/epoxide resin blends as matrices for unidirectional glass and carbon fiber and for balanced‐weave glass fiber cloth composites. The mechanical properties of the unreinforced resin and various composites were measured for specimens with matrices containing up to 35 percent of urethane. The properties of the unreinforced resin show very marked changes between 30 and 35 percent of urethane due, it is believed, to the existence of discrete regions of urethane polymer throughout the matrix. The transverse properties of the unidirectional carbon fiber composites are significantly enhanced by the presence of 20 percent of urethane in the matrix without, apart from a decrease in the shear modulus, any marked change in other properties. This could prove useful in the applications of carbon fiber composites. Results for glass fiber materials are less dramatic, possibly because of poorer adhesion between the glass fiber and the urethane. If this is indeed the cause of the results, it should be possible to bring about an improvement for glass fiber composites by using fibers coated with a suitable coupling agent.
Prediction of transport properties of composites from equations of elasticity
Authors: Mehta B. S. , Dibenedetto A. T. , Kardos J. L.
Published: December 2004

The mathematically‐analogous equations of elasticity were used to predict the transport properties of anisotropic composite films. Composite films of controlled structural and physical characteristics were prepared by embedding impermeable glass ribbons in a cellulose acetate matrix. Simple but approximately‐precise equations of composite moduli developed by Halpin and Tsai were used to predict the composite permeability in terms of the permeabilities of the constituent phases and a structure factor which is a measure of the filler reinforcement and signifies the resistance of the filler phase to the diffusive flow in the composite medium. The discrepancy between the theoretical predictions and experimental composite permeabilities has been explained in terms of diffusive flux lines not staying in a single direction. In the case of glass ribbons the diffusive1 flow lines tend to bend away from the ribbons (regions of lower permeabilities). The extent of influence of the filler phase to impede the overall composite permeation is a function of the geometry, orientation and volume fraction of the filler.
The effect of accelerated weathering on the degradation of polymeric films
Authors: Kimball W. H. , Munir Z. A.
Published: December 2004

The influence of artificial weathering on three general properties of films of high‐impact polystyrene (HIP), poly(ethylene terephthalate) (PET), and poly(vinyl chloride) (PVC) was investigated, Degradation resulting from weathering was investigated in terms of changes in the water vapor permeation, mechanical properties, and optical transmission. The diffusivities and permeabilities of these three materials were significantly altered by weathering at two levels of exposure. Films of HIP were embrittled at both levels of exposure, whereas the PET films were embrittled only at the high level of exposure. Films of PVC showed embrittlement at the highest level of exposure and the lowest test temperature. Changes in the optical properties were less significant, amounting to a relatively small decrease in the transmission of the films in the visible range.
Measurement of the PVT behavior of cis‐1,4‐polybutadiene
Authors: Barlow J. W.
Published: December 2004

The volume of cis‐1,4‐polybutadiene between 5 and 55°C and 1 and 3000 atmospheres was measured to within a relative error of 0.1 percent with an especially developed, bellows‐type dilatometer. The presence of a small transition near 55°C was indicated by analysis of the data and confirmed by differential thermal analysis.
High speed wire coating by withdrawal from a bath of viscoelastic liquid
Authors: Middleman Stanley
Published: December 2004

Data are presented for the thickness H∞ of liquid coating entrained by continuous withdrawal at speed U of a wire of radius R from the free surface of a large bath. For Newtonian fluids of viscosity μ, density ρ and surface tension σ, the data are carried out to coating speeds beyond the applicability of current theories, to Capillary numbers of nearly one hundred. In the high speed range the data, which cover several orders of magnitude in viscosity, can be well represented by the equation

for Uμ/σ = Nca > 3. All data presented are at an essentially constant Goucher number of 0.08, where NGo ≡ R(ρg/2σ)1/2. Data for viscoelastic fluids show phenomena quite distinct, qualitatively and quantitatively, from Newtonian observations. In particular, strongly elastic fluids show a markedly reduced ability to be entrained onto the wire. Further, the coating thickness appears to become independent of Capillary number at high speed.
A class of mathematical models for sorption of swelling solvents in glassy polymers
Authors: Astaluta G. , Sarti G. C.
Published: December 2004

A class of mathematical models for sorption of swelling solvents in glassy polymers is analyzed. The essential features of these models are the explicit consideration of the kinetics of swelling and of the driving force for swelling. It is shown that, even when all other elementary phenomena are modeled in the simplest possible way, all the experimentally observed features of the processes considered are correctly predicted.
Design and operation of screen packs
Authors: Carley James F. , Smith Wayne C.
Published: December 2004

A method is presented for calculating the pressure drop in a polymer melt flowing through single or packed screens from orifice‐rheometer data, screen dimensions and flow rate. A design plot encompassing standard square‐woven and twilled‐dutch screens greatly simplifies the calculation. The design relationships are based on the assumption that, for the narrow range of shear usually encountered in a screen pack, the flow behavior is adequately represented by the power law. These relationships were developed from theoretical arguments and wide‐ranging experimental evidence reported elsewhere (1). Several examples involving screen packs in extrusion service are worked out in detail, The quantitative implications of the screen‐pack equations for extruder scale‐up are discussed.
The effect of molecular weight in the crystallization kinetics of glassy nylon 6
Authors: Engler Philip , Carr Stephen H.
Published: December 2004

Crystallization of glassy nylon 6 has been investigated with differential scanning calorimetry and wide angle X‐ray diffraction in order to determine the effect of average molecular weight. Samples were prepared by quenching molten films between platens: chilled with liquid nitrogen. These films had number average molecular weights ranging from 10,000 to 42,000 and had polydispersity indices ranging from 2.0 to 3.1. Crystallization kinetics at large undercoolings were measured in terms of the systematic dependence of conversion half time, Avrami exponent and heat of crystallization. Number average molecular weight was observed to influence crystallization rate at large undercoolings through its effect on glass transition temperature. At intermediate undercoolings, molecular weight affected crystallization rate through terms other than the glass transition temperature. In addition, a dependence on the degree of order of the macromolecules, both prior to and after crystallization, was observed.
Annealing of drawn crystalline polymers
Authors: Peterlin A.
Published: December 2004

The annealing of drawn samples mobilizes the almost fully extended amorphous tie molecules which try to assume the thermodynamically required random conformations. The sample shrinks if annealed with free ends which permits the crystal blocks on different microfibrils and connected by almost fully extended taut tie molecules to move towards the position they had before plastic deformation. Hence the annealed sample has irretrievably lost most of its high axial elastic modulus which in the sample as drawn was caused by the high fraction of taut tie molecules. With fixed ends no shrinkage is possible so that the partial relaxation of interfibrillar taut tie molecules still lets them connect far away blocks. If their fraction is large enough so that in spite of the high surface to volume ratio which drastically depresses the crystallization temperature they can crystallize they do so after cooling to room temperature. The new axial crystalline bridges restore the high elastic modulus of the material before annealing, partially stabilize the sample against shrinkage during a new annealing, but also cause the dead bend effect which is the consequence of the replacement of flexible taut tie molecules in still amorphous conformation by rigid crystalline bridges. The drawing or extrusion at high temperature produces some annealing effects comparable with those of cold drawn material annealed with fixed ends.
Strength of discontinuous reinforced composites: I. Fiber reinforced composites
Authors: Halpin J. C. , Karoos J. L.
Published: December 2004

The strength of randomly oriented short fiber composites has been modeled by a quasi‐isotropic laminate. Lamination theory and a failure criterion will be used to approximate the stress‐strain response of a composite as it is loaded to failure. Experimental data are presented and compared with the maximum‐strain failure criterion.
Superdrawn filaments of polypropylene
Authors: Taylor W. N. , Clark E. S.
Published: December 2004

Filaments of polypropylene having remarkably high strength and modulus have been prepared by the two‐stage drawing process of Clark and Scott (4). In the first stage, un‐oriented extruded billet is rapidly drawn to the natural draw ratio of ca 7X in hot silicone oil. The second stage of draw, a post neck draw process termed superdrawing, requires a slow rate of draw at carefully controlled temperatures to achieve maximum property values; the optimum conditions appear to be close to 4 percent/min at 130°C, The highest mechanical properties obtained were a Young's modulus of 22 GPa (240 gdtex, 3 × 106 psi) and a tensile strength of 0.93 GPa (10 gdtex, 1.3 = 105 psi) with an elongation to break of 7 percent. The filaments show a distinctive dead bend lack of recovery, WAXS data indicate high orientation of the molecules. SAXS data show no scattering to a resolution of 40 nm which is interpreted in terms of a continuous crystal matrix in the superdrawn filament. SEM micrographs of fractured filaments reveal a morphology of large fibrils of lath like habit with a thickness of ca. 0.1 μm. A series of experiments relating mechanical properties to the rate and temperature of superdrawing is interpreted in terms of two competing mechanisms; shearing displacement of microfibrils and unfolding of chain‐fold blocks. Models are offered to explain the observed mechanical and physical property changes on superdrawing.
Effect of gamma radiation and annealing on ultra‐oriented polyethylene
Authors: Perkins W. G. , Stannett V. T. , Porter Roger S.
Published: December 2004

Filaments of ultra‐oriented high density polyethylene were solid‐state extruded at an extrusion (draw) ratio of 26 and subsequently irradiated under vacuum by a cobalt‐60 source at doses of 10,15, 20, 40 and 60 megarads (MRad). Several identically prepared but unirradiated strands were also tested. One set of samples at each dose was immersed in a silicone oil bath for one half hour at 128°C and one set was given no post‐irradiation thermal treatment. Characterization of the resultant morphologies included differential scanning calorimetry (DSC), birefringence, thermomechanical analysis (TMA), and tensile testing. Results from DSC measurements indicate that initial radiation crosslinking only slightly disrupts the crystal lattice, but on subsequent melting and re crystallization, the chains are unable to recrystallize effectively in their former habit. In all cases, melting point and crystallinity decrease with increasing radiation dose. Birefringence and TMA results indicate that orientation is not disrupted by irradiation. For unannealed samples, Young's modulus increases slightly then levels off while tensile strength and elongation at break increase initially, then drop, For annealed irradiated samples, Young's modulus rises at first, then levels off at higher doses. Tensile strength and elongation at break increase significantly with increasing radiation treatment, then essentially reach constant values at highest doses.
The thermal conductivity of several plastics determined by an improved line‐source apparatus
Authors: Underwood W. M. , Taylor J. R.
Published: December 2004

The line‐source method, previously used for measuring thermal conductivity of plastics, was increased in sensitivity so that automatic recording of data and data reduction by computer could be used, The correspondence between the underlying mathematics and the experiment is examined. The apparatus is described. The effect of experimental variables such as heating rate is determined‐ Measured values of thermal conductivity are reported for several commercial plastics, from room temperature, or lower, to processing temperatures. The precision of the results is excellent.