bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crack propagation in polycarbonate
Authors: Glover A. P. , Johnson F. A. , Radon J. C. 
Published: December 2004

AbstractCrack velocity measurements and fracture toughness tests have been carried out on extruded sheets of bisphenol‐A polycarbonate. Slow bend tests provided quasi‐staticK1cdata while dynamic initiation values were obtained from instrumented Charpy impact tests. In both types of tests high‐speed crack velocity measurements were made using conductive silver grids applied to the specimens. The variation ofK1cwith strain rate and temperature was found to be small and in general agreement with expectations from the relaxation properties of polycarbonate. Notch acuity was found to have little effect in that values ofK1cand crack velocity from specimens having the standard Charpy notch were similar to values obtained from sharp‐cracked specimens. Some anisotropy was present in the material and gave rise to a small variation in K1cvalues with direction of crack propagation. Crack velocity and also the fracture mode transition temperature showed considerable dependence upon orientation. It was thought that dynamic toughnessKd, was influenced more thanK1cby partial orientation of amorphous regions in the material and that the relaxation time for re‐orientation was probably significant here.
Kinetics of vapor and liquid transport in glassy polyblends of polystyrene and poly (2,6‐dimethyl 1,4‐phenylene oxide) Part II
Authors: Jacques C. H. M. , Hopfenberg H. B. 
Published: December 2004

AbstractThe kinetics of n‐hexane vapor and n‐hexane liquid sorption in solution cast films of polystyrene, poly(phenylene oxide), and blends of these homopolymers were studied over a significant range of temperature and penetrant activity. The kinetics of concomitant solvent crazing, apparent at high penetrant activities, were also monitored. In all cases the kinetics of sorption and crazing obeyed predominantly Case II or relaxation‐controlled behavior. Although the rates of crazing and sorption at high activities was much more rapid in the homopolymers than in the blends, the sorption rate at lower penetrant activities increased monotonically with increasing poly(phenylene oxide) content.These kinetic results qualitatively superimpose upon the equilibrium relationships reported in Part I of this series. Specifically, at a fixed temperature, the rate of crazing was virtually a unique function of equilibrium n‐hexane content independent of polymer composition and largely independent of penetrant activity. The coupling between rate of sorption and equilibrium penetrant content was dramatic. In limiting cases, the sorption rate increased by a factor of 10,000 apparently due to a twofold increase in equilibrium penetrant concentration. This seemingly complicated kinetic behavior is explained rather simply in terms of the equilibrium relationships between organic penetrants and polymeric glasses developed and interpreted in the first part of this series.
Antioxidant‐associated color problems in vinyl foams
Authors: Renshaw J. T. , Cannon J. A. 
Published: December 2004

AbstractInvestigations of chemically‐blown vinyl foam systems, based on electrical grade plasticizers, have shown that the inclusion of 2,2′‐bis (4‐hydroxyphenyl) propane (BPA) as an antioxidant results in color formation in the finished foam. Color formation appears to be due to interactions between BPA and the azodicarbonamide blowing agent. Metal ion(s) present in vinyl stabilizer/kickers are also shown to have an effect on color hue though not on color development per se. Mechanisms for the development of quinoidal and diazo color bodies, based on the reaction of BPA and azodicarbonamide are postulated. Based on these reaction mechanisms, it is shown that it is possible to choose an antioxidant that will not interact with azodicarbonamide. A rudimentary screening procedure is described for evaluating these systems.
Photochemistry in the solid phase
Authors: Guillet J. E. 
Published: December 2004

AbstractClassical photochemistry is an ancient branch of chemistry, but in the past its practitioners have restricted their interest primarily to studies in the gas or liquid phases. However the practical applications of photochemistry in recent years have led to an increasing interest in photoreactions which occur in the solid phase, particularly in polymeric systems. One of the first areas of practical interest has been in stabilizing plastic and other polymeric systems against photodegradative reactions initiated by solar radiation. More recently photoreactions in polymers have been used extensively in recording and reproducing photographic and other images.
Photocrosslinkable polyphosphonates having unusual resistance to acids
Authors: Borden Douglas G. 
Published: December 2004

AbstractThe resistance of various linear condensation polymers to acid or base hydrolysis is dependent upon the nature of the linkages in the polymer chain. Aryl polysulfonates having a styrylketone sensitizing group have been shown to be particularly resistant to attack by strong bases. Similar phosphorouscontaining polymers have been prepared and those with the arylphosphonate, thiophosphonate, and phosphate linkages have been found resistant to attack by such acids as ferric chloride. Using a solution polymerization method, these phosphorous polymers and also those containing the phosphite, phosphonite, and phosphorane linkages may readily be prepared. A comparison has been made of the resistance of these polymers and of the corresponding polycarbonates, polysulfonates, and polyesters to various bases and to ferric chloride solutions.
Mechanism of refractive index increase in photosensitized poly(methyl methacrylate)
Authors: Bowden M. J. , Chandross E. A. , Kaminow I. P. 
Published: December 2004

AbstractPoly(methyl methacrylate) prepared under special circumstances exhibits a substantial increase in refractive index after irradiation with ultraviolet light. The essential step in the preparation is peroxidation of the monomer prior to polymerization. This increase in refractive index results from a photo‐induced polymerization of unreacted monomer (1‐2 percent) within the film which produces an increase in density (and hence refractive index) in the irradiated region. It is believed that peroxides, both polymeric and monomeric, act as photoinitiators. Sensitivity depends on the concentration of photoinitiator but the absolute value of Δn depends on the amount of unreacted monomer.
Computer simulation study of images in contact and near‐contact printing
Authors: Lin B. J. 
Published: December 2004

AbstractVersatile computer programs capable of simulating near‐contact images from arbitrary objects and illumination were reported. Their capability was demonstrated in examples of combinations of different types of object and illumination. From the specific examples, we were able to derive certain general rules: (1) Polychromatic illumination is always better than monochromatic illumination. (Besides observing the examples given above, polychromatic illumination also helps when standing waves in photoresist are considered.) (2) Negative masks are easier to print than positive ones. Note that a negative mask in the sense of optical diffraction means smaller dimension for transparent parts of the mask. (3) Some well designed irregularities in the mask pattern improves the image. (4) The effective depth tolerance is between the limits set by the focussing effect and the image spreading effect. (5) Holographic mask should relax flatness and exposure tolerance.
Flash exposure system for thin photoresist films
Authors: O'Hora D. E. , Beuschel W. F. 
Published: December 2004

AbstractThe formation of an image in a photoresist during photolithographic processing requires the exposure of the photoresist through a mask to a light source in the spectral region to which the photoresist is sensitive. The functional advantage of the flash exposure of photoresist is presented, which includes the elimination of oxygen effects, the reduction of diffraction and standing wave effects, and the enhancement of pattern‐edge acuity. The effects of both broad and narrow band sources are also shown with emphasis on proximity printing techniques. Finally, the optical, electrical and physical design parameters for a practical flash exposure system are discussed.
The interaction of 5 KeV electrons with polymers of methyl isopropenyl ketone
Authors: Levine Aaron W. , Kaplan Michael , Poliniak Eugene S. 
Published: December 2004

AbstractPoly(methyl isopropenyl ketone) (PMIPK) degrades upon exposure to 5 keV electrons. Using a scanning electron microscope to expose fine‐line raster patterns in thin films of this polymer and subsequently solvent‐developing the thus‐degraded regions, sharp walled troughs are observed, the width of which is a measure of the sensitivity to degradation. Copolymers with several vinyl monomers were prepared and the sensitivities of these were similarly determined. Information relevant to the mechanism of depolymerization was obtained by comparing homopolymers with copolymers and by the use of additives in the irradiated polymer films. Examples of potential device‐fabrication techniques using PMIPK resist are given.
Vapor development of poly(olefin sulfone) resists
Authors: Bowden M. J. , Thompson L. F. 
Published: December 2004

AbstractPoly(2‐methyl pentene‐1) sulfone undergoes scission followed by rapid chain depolymerization when irradiated with 5‐20 kV electrons. Several parameters which affect the rate of this process, termed vapor development, were evaluated, viz., molecular weight, dose rate, temperature, accelerating voltage and film thickness. While it was never really possible to remove 100 percent of the film, it was possible to remove > 99 percent at reasonably low doses (∼ 10−6 coul/cm−2) using high temperatures (∼ 100°C) and low accelerating voltage (5 kV). Some lithographic details of this process are also described.
A melting model for reciprocating screw injection‐molding machines
Authors: Lipshitz S. D. , Lavie R. , Tadmor Z. 
Published: December 2004

AbstractA theoretical model for melting in reciprocating screw injection molding machines is proposed. The model permits the calculation of the solid bed profile as a function of time during the injection cycle. It consists of a dynamic extrusion melting model for the rotation period, a transient heat conduction model with a phase transition for the screw rest period, and a proposed model for the drifting of the beginning of melting during the injection cycle.
Elastic fracture of polystyrene solutions
Authors: Southern J. H. , Paul D. R. 
Published: December 2004

AbstractBased on the assumption of a constant critical shear strain, an expression for the critical stress at the onset of entrance fracture as a function of polymer concentration has been developed. Experimental results with 10‐25 percent narrow distribution, high molecular weight polystyrene‐benzene solutions show the critical stress to be much lower than that for the polymer melt and in agreement with predicted values. This result is all the more impressive when the contrast in flow behavior at the capillary entrance for melts and solutions is observed. Instead of the rotating toroidal vortices surrounding a 90‐deg material entrance cone observed with polystyrene melt, cine movies of the solution flow birefringence patterns in the capillary entrance region reveal only a stagnant zone surrounding a narrow cone less than 20 deg. At fracture, the cone axis moves in a rotary path circulating about the capillary axis without undergoing the flow discontinuities typical of melt behavior.
Dilatometric studies of polymers undergoing high and low rate tensile deformation
Authors: Cessna L. C. 
Published: December 2004

AbstractSpecific volume change and stress‐strain data were obtained simultaneously during tensile deformation on several plastics known to be resistant to impact loading. Tensile deformation rates of 20 percent/minute and 106 percent/minute and temperatures of −190° to 55°C were employed. A common sequence of deformation modes was observed in all materials studied (rubber modified acrylics and styrene, ABS materials, polycarbonate, impact grade polypropylenes, and high density polyethylene). In all cases the major mode of deformation to failure at low rates and/or higher temperatures is volume conserving and primarily a shear flow process. At higher rates of deformation or lower temperatures, a transition occurs and the specific volume of the material increases in direct proportionality to the tensile strain above the apparent yield point. Volume increases of 17 to 50% were observed and these were equal to 85 percent or more of the observed tensile strain at failure. These observations indicate that microcavitation may be the major process available for the absorption of mechanical energy at impact rates in plastic materials.
Thermal expansion instability and effect on creep of a highly crosslinked polyurethane
Authors: Findley William Nichols , Reed Ray Merritt 
Published: December 2004

AbstractIt was found after heating that the thermal expansion of polyurethane decreased markedly in several hundred hours at constant temperature; after cooling the thermal contraction decreased with time but more slowly. The role of cross‐linking as a possible cause of this effect is discussed. Creep during the expanded phase after heating is shown to be much greater than creep after thermal expansion has stabilized at the same temperature. Experiments are described which suggest that the effect of temperature on creep results primarily from thermal expansion rather than from thermal oscillation.
A design approach to a computer‐controlled injection‐molding machine
Authors: Ma Carl Y. W. 
Published: December 2004

AbstractPlastics injection molding is a complex, multi‐variable process which has not yet been clarified. The hardware controller is difficult to build without a realistic mathematical model. One powerful technique for solving such a difficulty is to employ digital control technology which can utilize sophisticated control strategies in order to optimize the system performance. Machine operation and resultant production can be tightly controlled by using computer monitoring, data storage and data logging. This paper presents elements of the various problems that process engineers may encounter in designing a computer‐controlled system for plastics injection‐molding machinery. The variables of the process and a functional analysis of process control are discussed. A hardware system design; including specification of computer, selection of peripheral devices, system design, and input/output interfacing; is presented.
Viscosity and shear modulus of PVC‐plastisols during gelation and fusion
Authors: Cayrol B. , Klason C. , Kubát J. 
Published: December 2004

AbstractThe Contraves balance rheometer has been used in a study of the gelation and fusion process of three DOP‐based PVC‐plastisols and the results compared with those obtained with the Brabender plastograph. The tensile properties of samples fused at different temperatures have also been determined. The rheometer results relate to the temperature dependence of the viscosity, shear modulus, and loss angle of the plastisols used. The viscosity‐ and modulus‐temperature curves are to some extent reminiscent of the torque‐temperature curves obtained with the plastograph; the fusion temperatures are slightly different. The loss‐angle‐temperature curves measured with the rheometer exhibit sharp maxima in the vicinity of the Tg‐point of the base polymer. The shear modulus decreases with time when the temperature is kept constant (above the fusion point). This effect is possibly associated with crystallite melting. The temperature necessary to reach the maximum strength plateau of films fused at various temperatures was found to agree (within 10°C) with the maximum in the modulus‐temperature curves (minimum in loss‐angle‐temperature curves) when the rheometer shear rate was sufficiently low. On the whole, the rheometer allows for better temperature control. Also, the fact that the results are given in terms of viscosity and shear modulus may have some advantage in interpreting gelation and fusion data.
Ultimate behavior of dry and water‐swollen polymer network/glass bead composites
Authors: Nicolais L. , Acierno D. , Janáček J. 
Published: December 2004

AbstractTensile properties of a poly(2‐hydroxyethyl methacrylate) (PHEMA) network filled with various amounts of glass beads, in the dry and the equilibrium water‐swollen states, have been studied below and above Tg. The temperature ranged from 5° C to 170° C and the volume fraction of the filler was up to 50 percent. In the glassy region it has been found that the temperature at which the transition from brittle to ductiel behavior occurs is increased by the presence of the filler. In the brittle zone the strength of the composites is decreased by the presence of the filler and can be predicted by using a finite element method; in the ductile zone, however, the strength of the composites reaches that of the unfilled polymer.In the rubbery region failure envelopes have been obtained for both dry and swollen PHEMA/glass bead composites. Using a double shift procedure all the data have been superimposed to obtain universal failure envelopes for the two different states. The dependence of the shift factors on filler content is discussed.
Fluid mechanical analysis of injection mold filling
Authors: White James Lindsay 
Published: December 2004

AbstractThe hydrodynamics of the filling of a rectangular mold cavity by a molten polymer is considered in terms of lubrication theory. Both isothermal and nonisothermal mold filling are analyzed. The relationship of the velocity field to the cavity geometry and temperature dependence of the rheological properties is predicted. Increasing the activation energy of viscous flow increases the tendency for channeling of melt through the center of the cavity. The results are compared to the experimental observations of our previous studies.
Liquid (melt) heat capacities and heats of vaporization of oligomers of poly(hexamethylene sebacate)
Authors: Phillips J. C. , Wall L. A. , Aldridge Mary H. 
Published: December 2004

AbstractThe liquid heat capacities and heats of vaporization of three linear esters of poly(hexamethylene sebacate) with hexylcapped end groups (M(mol. wt.) = 370, 655, and 939) have been determined. The heats of vaporization of the oligomers measured at a mean temperature were corrected to 323.15 to 523.15°K by use of the experimental liquid (melt) heat capacities and the calculated gas heat capacities. The corrected heats of vaporization were fitted to the equation ΔHv = S(T)Mα + I(T), where the temperature dependence of the slope and intercept are represented, respectively, as S(T) = ClnT + Ko and I(T) = a T + bo, and α is an exponent. The results indicate (at corresponding molecular weights and constant temperature) that the ratio of the liquid heat capacities of the oligomer ester and the n‐alkane, and similarly the ratio of the heats of vaporization, depend on the number of carboxyl groups in the oligomer ester chain.
Effect of mold temperature on the morphology and properties of polypropylene: I. A propylene‐ethylene copolymer
Authors: Henke S. J. , Smith C. E. , Abbott R. F. 
Published: December 2004

AbstractThe mechanical properties of a propylene‐ethylene copolymer resin depend strongly on the mold temperature employed during injection molding. Average spherulite size correlates well with most physical properties; good impact properties are related to small average size, and high heat distortion temperatures to large average size. Tensile specimens have three distinct regions when viewed through crossed polars. The outer region (Region 1) does not contain spherulites, but Regions 2 and 3 do. The largest spherulites are found in Region 3, the center of the specimen. Region 1 has a molecular weight higher than that of the other two regions.
Polymer property enhancement by solid‐state forming
Authors: Broutman Lawrence J. 
Published: December 2004

AbstractThe alteration of the physical properties of a polymer by the use of forming techniques which are applied below the melt or glass transition temperature of the polymer has been discussed. The influence of cold rolling (rolling accomplished at room temperature) on the mechanical properties of amorphous polymers was first briefly reviewed (1). The specific effect of rolling on the toughness of polycarbonates, as measured by notched Izod impact strength, was discussed in detail and is summarized in (2). The role of crystallinity in further enhancing the mechanical properties of polycarbonate and the combined effect of rolling and crystallinity was also described and is discussed in more detail in (3). Other amorphous polymers were also discussed, particularly the effect of rolling on the notched Izod impact strength (4). For most polymers studied, a large increase in impact strength occurs for small reductions in thickness and a maximum occurs at a given thickness reduction beyond which the ductility of the material is exhausted. The increase in impact strength is not only a result of molecular orientation but also a function of residual stress placed in the sheet by the rolling process.In addition to the studies on amorphous polymers, recent studies (5, 6) were described on the high‐pressure nonisothermal compression molding of linear polyethylenes. Mold pressures up to 80,000 psi were used and several different polyethylenes having various molecular weights (up to 106) were investigated. It was shown that the modulus of elasticity of polyethylene can be increased by a factor of two when the mold pressure is increased to 80,000 psi. A detailed discussion of the changes in morphology responsible for this increased stiffness is presented in (6).
Measurement of aging effects of ABS polymers
Authors: Casale A. , Salvatore O. , Pizzigoni G. 
Published: December 2004

AbstractABS (acrylonitrile‐butadiene‐styrene) plastics are one of the most common two‐phase commercial polymer systems. They consist of a continuous rigid phase (styrene‐acrylonitrile co‐polymer) in which the elastomer phase (polybutadiene grafted with styrene and acrylonitrile) is finely dispersed in the form of spherical particles. Because of their properties and relatively low cost compared to other engineering thermoplastics, ABS resins are now being used increasingly in fields of application involving severe aging. The polybutadiene content, however, poses a problem in relation to ABS aging resistance, since it is a prime site for degradative attack at double bonds and tertiary carbon atoms. The present paper presents a concise account of the methods used in our labortory for measuring ABS aging. As an example, ABS degradation during processing and during natural and artificial light aging are discussed in more detail.
Effects of mixing on polymerizations in batch reactors: Comparison of catalytic and ionizing radiation initiations
Authors: Chen H. T. , Steenrod J. 
Published: December 2004

AbstractThe effects of mixing on polymerizations in batch reactors are examined theoretically for initiations by thermal decomposition of catalyst and by absorption of ionizing radiation. Mathematical expressions for predicting the first three moments of the dead polymer size distribution are presented. Two extreme mixing states, perfect and no mixing, are considered. It is shown that in batch reactors mixing in any direction in which nonuniform initiations exist increases the polymerization rate and the number average molecular weight and decreases the weight average and thus the polydispersity.