High Impact Polystyrene Sheets Research Articles

Numerical and experimental analysis of HIPS sheets in thermoforming process

In this study, two different thermoforming molds, i.e., male and female, were prepared and used to conduct different tests at various heating times and evacuation powers. High impact polystyrene sheets of 0.5 mm thick were used to produce the cups with two vacuum and drape forming process. The experimental results showed that a more uniform thickness distribution could be obtained by increasing the heating time for the female mold. However, for the male mold, the heating time must be decreased in order to achieve a more uniform thickness distribution. Our findings showed that biaxial stretching was dominant in the vacuum forming, while uniaxial stretching was dominant in the drape forming. A finite element simulation of the vacuum forming process was also conducted to present a simple and accurate study of the forming process. In this work, a hyperviscoelastic constitutive model was used for modeling the high impact polystyrene behavior at forming temperature. The thickness distribution obtained by the finite element analysis is in a good agreement with the experimental results. In addition, the effect of friction coefficient was investigated by finite element analysis on the thickness distribution of the cup.

Studies on the stretching behaviour of medium gauge high impact polystyrene sheets during positive thermoforming

High impact polystyrene sheets (HIPS) of 1.5 mm and 2.5 mm thicknesses were thermoformed on moulds of different parameters at sheet heating temperatures of 130℃ and 140℃. Formability studies indicated no difference in wall thickness distribution at different sheet temperatures. Due to non-uniform stretching of the sheet, wall thickness distribution along the slant length was found to have three regions. In the regions near the mould corner and clamp point, wall thickness was found to decrease with increase in distance from the corner, in these zones. The decrease near the corner was much greater and sharper than that near the clamp point. The decrease in both regions was found to increase at higher depths of draw and decrease at higher draft angles. In the intermediate portion of the slant length, no significant variation in wall thickness was observed.

Photochemical Degradation of Recycled High-Impact Polystyrene

Abstract Photooxidative aging of high-impact polystyrene sheets at 25°C was followed for different intervals of 25, 40, 50, 75, and 80 h. Five different types of samples were used, viz. virgin, and recycled once, twice, three, and four times. The optical properties of exposed samples exhibited changes as a result of discoloration. The transmittance and reflection deceases whereas absorbance increases with increasing recycling of high-impact polystyrene.

Effect of Thermal Aging on the Thermal Stability of Recycled High-Impact Polystyrene

Abstract Thermo-oxidative aging of high-impact polystyrene sheets at 100°C was followed for a period of 1300 h. Four different types of samples were used, viz., virgin and recycled once, three, and five times. The samples exhibited systemic changes as a result of discoloration. The DTA of those samples indicates a rapid deterioration in thermal stability as well as deterioration in the optical properties.

Effect of thermal ageing on the optical properties of recycled high impact polystyrene

Thermo-oxidative ageing of high impact polystyrene sheets at 100°C was followed for a period of 1300 h. Six different types of samples were used, viz. virgin, and recycled once, twice, three times, four times and five times. The optical properties of aged samples exhibited systematic changes as a result of discoloration. The absorbance increased whereas transmittance and reflectance decreased. The more the samples were recycled the greater was the deterioration in the optical properties, thus making UV-visible spectrophotometry, a simple tool, useful for differentiating recycled from virgin samples.

Motion and Structural Response of a Hydroelastic Semi-Submersible Model to Waves and Ice Impacts

This paper presents the motion and structural responses of a model that is structurally and dynamically similar to a typical semi-submersible platform. The model is fabricated of high impact polystyrene sheets, 0.78 mm (0.03 in.) thick, and cellulose acetate butyrate (CAB) tubes (for bracings), 1.58 mm (0.06 in.) thick. The response of the model to regular and irregular waves under operating/survival conditions and impacts of modeled bergy-bits (prototype weights of 1000 t and 2000 t traveling at speeds of 1.0 to 4.0 m/s) was determined. In addition, the response of a damaged-corner-column semi-submersible to survival wave conditions was also examined. The motion and structural responses were monitored using 30 strain gages, an accelerometer and four potentiometer devices. The impact loads were simulated by weights swinging in a pendulum mode in still water. The motion RAOs, stress RAOs, PSDs of stresses, impact loads versus time histories, etc., are computed and compared with published values. There is a very good agreement between the present experimental/analytical results and other results published earlier for the motion response. It was found that the theoretical models tend to overestimate the structural response at short wave periods and underestimate it at long periods.

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.

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.