bluuebunny/crossref_metadata_2025_split huggingface dataset:
A forced torsional oscillator for dynamic mechanical measurements
Authors: Davis William M. , Macosko Christopher W. 
Published: December 2004

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractWe 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

AbstractPolyimides 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

AbstractA 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

AbstractA 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

AbstractTriblock 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

AbstractA 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

AbstractThe 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

AbstractESR 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

AbstractButadiene‐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

AbstractMultiblock , 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

AbstractA 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

AbstractIn 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

AbstractIt 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

AbstractIn 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

AbstractThe 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

AbstractIn 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

AbstractThe 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.