Polystyrene Sheets Research Articles

The effect of film thickness and sample history on the parameters describing transport in glassy polymers

The effect of a characteristic dimension of a glassy polymeric specimen on the kinetic mechanism controlling unidirectional absorption of organic vapors and liquids in glassy polymers is demonstrated by comparing n-alkane absorption experiments in microspheres, spheres, films, and sheets of polystyrene. Absorption in submicron microspheres is controlled by Fickian diffusion whereas, under otherwise identical boundary conditions, films (ca. 75μm thick) and spheres (ca. 184 μm in diameter) sorb according to Case II absorption kinetics. Thinner films (35 μm thick) sorb by Super Case II kinetics and relatively thick sheets (2000 μm thick) sorb initially by Case II kinetics but, at long times, diffusion through the outer swollen region contributes significantly to the overall resistance to mass transfer and the rate of absorption decreases progressively with time. p]The rather short experimental times, afforded by the exceedingly small mean diameter of the narrowly distributed microsphere powder sample, permitted convenient characterization of the effects of preswelling, sorption-desorption cycling, and annealing on the kinetics and apparent equilibria of sorption. History effects were quite dramatic and were related to glassy state relaxations initiated by the various thermal and swelling histories imposed upon the glassy microspheres. p]Prediction of sorption and permeation behavior in membranes, from kinetic and equilibrium parameters determined experimentally on film and powder samples, requires explicit recognition of these dimensional and history effects. These effects do not appear to be related to any special properties of this polymer-penetrant system.

Characterization and effects of n-alkane swelling of polystyrene sheets

Detailed penetration kinetics of a series of normal alkanes in 2 mm polystyrene sheets have been determined by an optical method over a broad range of temperatures encompassing the effective glass transition temperature of the resulting sheets. Whereas earlier thin film results, involving identical thermodynamic boundary conditions, have been characterized by ideal Case II transport, the results obtained here appear to be confounded at long times by a significant diffusional resistance in the swollen surface regions surrounding the unplasticized central core of these relatively thick sheets. At relatively low temperatures, the rate determining relaxations, at the boundary between swollen and unswollen polymer, are sufficiently slow to ensure ideal Case II transport over the entire course of the sorption history. These swelling experiments were complemented by Clash—Berg measurements of the temperature-dependence of the 10 sec torsional shear moduli of partly penetrated sheets, completely swollen sheets and unswollen sheets. The Clash—Berg results suggest that the T g of the n-hexane swollen sheet is approximately 20°C and that the properties of the swollen regions of partly penetrated specimens are identical to the properties of the completely swollen sheet. A model based on the core-shell morphology, induced by the prior swelling, satisfactorily describes the observed mechanical properties of these swelling induced composites.

Fatigue fracture processes in polystyrene

Fatigue crack growth characteristics in polystyrene were studied as a function of stress intensity factor range and cyclic frequency. Precracked single edge notched and compact-tension type specimens made from commercially available polystyrene sheet (mol.wt. =2.7×105) were cycled under constant load at frequencies of 0.1, 1, 10 and 100 Hz, producing growth rates ranging from 4×10−7 to 4×10−3 cm/cycle. For a given stress intensity level, fatigue crack growth rates were found to decrease with increasing frequency, the effect being strongest at high stress intensity values. The variable frequency sensitivity of this polymer over the test range studied was explained in terms of a variable creep component. The macroscopic appearance of the fracture surface showed two distinct regions. At low stress intensity values, a highly reflective, mirror-like surface was observed which transformed to a rougher, cloudy surface structure with increasing stress intensity level. Raising the test frequency shifted the transition between these areas to higher values of stress intensity. The microscopic appearance of the mirror region revealed evidence of crack propagation through a single craze while the appearance of the rough region indicated crack growth through many crazes, all nominally normal to the applied stress axis. Electron fractographic examination of the mirror region revealed many parallel bands perpendicular to the direction of crack growth, each formed by a discontinuous crack growth process as a result of many fatigue cycles. The size of these bands was found to be consistent with the dimension of the crack tip plastic zone as computed by the Dugdale model. At high stress intensity levels a new set of parallel markings was found in the cloudy region which corresponded to the incremental crack extension for an individual loading cycle.

Thickness variation in the thermoforming of poly(methyl methacrylate) and high‐impact polystyrene sheets

AbstractThe influence of material flow properties on the variation of wall thickness in a thermoformed part was investigated by measuring the thickness reduction at the pole of free‐formed axisymmetric domes of poly(methyl methacrylate) and high‐impact polystyrene. It was found that at a given pole height, the thickness reduction in poly(methyl methacrylate) was less than in high‐impact polystyrene, i.e., the wall thickness in a part formed from poly(methyl methacrylate) will be more uniform than in a part formed from high‐impact polystyrene by the same technique. This difference in formability was ascribed to a difference in the dependence of the flow stress σ at the thermoforming temperatures on time. The flow stress of both materials was given by σ = Ktm′ϵn, but whereas n was approximately 1 for both materials, m′ was −0.052 and −0.33 for poly(methyl methacrylate) and high‐impact polystyrene, respectively. A physical argument and simple analysis led to the conclusion that a large (negative) value of the “stress relaxation index” in a material reduces the degree of uniformity of sheet thickness in a formed part.

Sensory irritation evoked by plastic decomposition products.

Polystyrene sheets and foams and polycarbonate sheets were used. A known amount was placed in a combustion chamber of 12 liters in volume and combustion (candle type downward burning) was initiated by ignition with a Bunsen gas burner. The airflow through the combustion chamber was maintained at 17 liters/min and air was enriched with oxygen (30% O2) for the polycarbonate. The air exhausted from the combustion chamber was diluted and directed to a glass exposure chamber. (2.3 liters volume) to which was attached ifour tubes each containing one mouse with the head of the animal protruding in the exposure chamber. Characteristic decreases in respiratory rate were used as an index of sensory irritation of the upper respiratory tract and monitored during and following exposure to the combustion products. A dose-response relationship was obtained with all three materials and indicated that the combustion products of polystyrene films were the most irritating. When a known sensory irritant was incorporated into...

A Thin, Flat, Parallel Plate Ionization Chamber for Electron Beam Depth-Dose Measurements

A parallel plate ionization chamber of 0.2-cm plate separation and 0.6-mm3 sensitive volume was constructed of easily machinable white opaque high impact polystyrene sheets and is very useful in the depth-dose measurement of electron beams. The design features and performance characteristics are given.

A mathematical model for predicting dynamic behavior of a plasticating extruder

AbstractA mathematical model was developed to predict the dynamic behavior of flowrate and melt temperature in a plasticating extruder caused by changes in operating variables such as screw speed, back pressure and barrel temperature. The model has application for on‐line computer control of an extrusion process or for simulation purposes off‐line. Experimental data for developing the model was obtained from a 2½ in. diameter plasticating extruder producing high impact polystyrene sheet.

Absorption coefficient of unpigmented poly(methyl methacrylate), polystyrene, polycarbonate, and poly(4‐methylpentene‐1) sheets

Journal of Applied Polymer ScienceVolume 15, Issue 7 p. 1803-1807 NoteFree Access Absorption coefficient of unpigmented poly(methyl methacrylate), polystyrene, polycarbonate, and poly(4-methylpentene-1) sheets R. C. Progelhof, R. C. Progelhof Department of Mechanical Engineering, Newark College of Engineering Newark, New Jersey 07102Search for more papers by this authorJ. Franey, J. Franey Department of Mechanical Engineering, Newark College of Engineering Newark, New Jersey 07102Search for more papers by this authorT. W. Haas, T. W. Haas Department of Mechanical Engineering, Newark College of Engineering Newark, New Jersey 07102Search for more papers by this author R. C. Progelhof, R. C. Progelhof Department of Mechanical Engineering, Newark College of Engineering Newark, New Jersey 07102Search for more papers by this authorJ. Franey, J. Franey Department of Mechanical Engineering, Newark College of Engineering Newark, New Jersey 07102Search for more papers by this authorT. W. Haas, T. W. Haas Department of Mechanical Engineering, Newark College of Engineering Newark, New Jersey 07102Search for more papers by this author First published: July 1971 https://doi.org/10.1002/app.1971.070150724Citations: 17AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume15, Issue7July 1971Pages 1803-1807 ReferencesRelatedInformation

Craze distribution around cracks in polystyrene

The distribution of surface crazes in the vicinity of a stationary edge crack in a polystyrene sheet in tension is compared with the stress fields already investigated experimentally by Post. It is shown that the extent of crazing corresponds closely with the maximum principal stress contours determined experimentally and that the shapes of the crazes indicate that they grow along directions parallel to the minor principal stress axis.

Waveguide admittance for radiation into plasma layers--Theory and experiment

Measured admittance of an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</tex> -band waveguide radiating into dielectric and plasma layers is compared with variationally computed admittance figures. The waveguide admittance measurements for polystyrene sheets of varying thicknesses compared closely with calculations. The admittance is computed first by assuming the principal waveguide mode, and second by using a superposition of sine and shifted cosine waves as trial functions for aperture fields. Although the aperture fields are shown to differ significantly in the two cases, the computed admittance data are nearly the same because of the stationary character of the admittance expression. The admittance measurements for plasma layers are made during the diffusion controlled afterglow of a pulsed discharge contained in a bell-shaped vessel. Thin Teflon sheets are used to confine the plasma layers to an approximate size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5 \times 5 \times \frac{3}{4}</tex> inches. The electron density of the plasma profile is measured by Langmuir probes at various times during the afterglow. The plasma density was measured over approximately 70 percent of the thickness of the plasma layers, and was found to be nearly constant in this range which excluded regions near the boundary. Numerical solutions of the equations for ambipolar diffusion during the afterglow in a rectangular geometry show that the lateral plasma density variations are negligible in the vicinity of the waveguide. The measured admittance and plasma density data are shown to agree with calculations made for homogeneous plasma layers, if a correction is made for elevated ion temperatures for times of approximately 10 to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20 \mu</tex> s following the discharge. Several computational models consider plasma stratifications near the boundary of the plasma layer but they do not improve the agreement between measurement and calculations.

Equipment and Materials

A wall‐lining material for home decorators is being marketed by Telcon Plastics Ltd., Green Street Green, Orpington, Kent, Tel.: 55685. It bears the name Telstrene and is a special grade of the expanded polystyrene sheet introduced to the packaging trade in 1963. This wall insulation is 0.015 in. thick, with a satin‐like surface, and is available in rolls 24 in. wide and 11 yd. long. It can be applied to plaster walls with a polyvinyl alcohol‐type adhesive, using ordinary paperhanging technique. It is proof against water and water vapour and completely rotproof and its structure of small closed cells makes it an excellent thermal insulator and condensation preventer.

Model experiments on refraction arrivals from a linear transition layer

abstract Ultrasonic model experiments were performed to examine the effect of a transition layer on the frequency spectra of refraction arrivals. Two-dimensional, layered structures with transition layers constructed from polystyrene and Plexiglas sheets served as the models. The materials were so chosen that the model simulated the relation between the crust and the mantle. A pulsed sinusoidal wave with variable frequency and a square-wave pulse were used. The amplitude of the refraction arrivals showed a rapid decrease with increasing frequency starting at a frequency f0 which was found to have the value 1.7 k, where k is the velocity gradient in the transition layer. It is expected that a similar effect will be observed for the refraction arrivals from the Mohorovičić discontinuity if a transition layer exists at the boundary.

Aluminized Polystyrene Light Pipes

First Page

Absorption Measurements of Ultrasonic Waves in Plastic Sheets

Absorption coefficients of ultrasonic compressional waves in polystyrene and Plexiglas sheets were measured for use in model experiments of elastic wave propagation. A pulsed sinusoidal wave of variable frequency was used. In the frequency range of 30 to 200 kc/sec, the relations between the absorption coefficient α (Np/cm) and frequency f (kc/sec) were found to be approximated by α=7.3×10−5 f1.4 for polystyrene, and α=0.054 log f−0.080 for Plexiglas.

High gloss of extruded high impact polystyrene sheet. A microscopical study of sheet morphology

High gloss of extruded high impact polystyrene sheet. A microscopical study of sheet morphology

High gloss of extruded high impact polystyrene sheet. A microscopical study of sheet morphology

AbstractMorphological changes effected in the two‐phase high impact polystyrene system by several methods of securing high surface gloss of extruded sheet were studied microscopically. In the glazing process changes occur in refractive index of the copolymer particles and in the matrix. Excessive glazing may result in oxidative damage. The effects of temperature and oxidation and temperature alone on the copolymer particles have been investigated.

SURFACE-WAVE PROPAGATION OVER PLANE-LAYERED DIELECTRICS

A two-layer dielectric system, consisting of a thin polystyrene sheet on top of water, is examined as a possible guiding structure for surface waves. Experimental investigations, at a frequency of 9.35 Gc/sec, of the phase velocity of the waves close to the surface of the upper layer, and the power variation with height above it, are described. A slow wave was found to propagate near the surface and its phase velocity was found to agree with that predicted theoretically for a TM surface wave. Qualitative agreement between the experimental and theoretical power variation with height confirmed the existence of a surface-wave contribution to the total field above such a layered dielectric system.

Microscopical measurement of orientation of high-impact polystyrene extruded sheet

The polystyrene–butadiene copolymer particles in high-impact polystyrene sheet respond to forces imposed on the sheet. Measurement of the ellipticity of these particles in thin microtome sections provides a measure of orientation of extruded sheet.

Thin cation-exchange foils

Treatment of commercial polystyrene sheets with fuming sulfuric acid produces a thin layer of cation exchanger. The ion exchange capacity of the layer is measured by an isotope dilution procedure which utilizes Th 228 and Th 232. At the same time the thickness is found from the yield of Ra 224 which escapes from the foils as α-decay recoils. A specific capacity of 5.6 milliequivalents per gram can readily be obtained, and the thickness can be varied from a few to several hundred micrograms/cm 2. The foils have been used for simple and fast preparation of α sources.

Photoelastic Properties of Polystyrene in the Glassy State. II. Effect of Temperature

The effect of temperature on the stress-optical coefficient of polystyrene was measured at twelve different temperatures from −195° to +24°C using samples of unoriented polystyrene sheet. The stress-optical coefficient appears to decrease with temperature from a value of about +17 brewsters at −195°C to a value of about +10 brewsters at room temperature. The elastic (Young's) modulus of polystyrene was also measured as a function of temperature using a flexural technique and was found to decrease linearly with temperature from 6.36×105 psi at −198° to 4.65×105 psi at +24°C. A curve of strain-optical coefficient vs temperature was obtained by multiplying stress-optical and modulus values; this curve increases with decreasing temperature from about +0.03 at +24° to +0.073 at −195°C.