Abstract
The effect of free quenching on the mechanical, thermal, and thermophysical properties of polystyrene has been investigated. Three different thermal treatments were investigated: a first quenching from the melt state to different temperatures, a second quenching from °C, and finally an annealing. The results have shown that a slight improvement of the impact strength can be obtained after a second quenching at 40°C, and a correlation between the mechanical and thermal properties is observed. The improvement of this property was obtained at the expense of other properties such as the elastic modulus, density, hardness, and the heat distortion temperature (HDT). The little improvement of the impact strength after the second quenching is probably linked to the existence of a relaxation mode located around 40°C. However, no effects have been shown on the thermophysical properties.
Highlights
In a previous study [1], the effect of different heat treatments on the mechanical properties of polycarbonate (PC) was investigated
The effect of the quenching process on the mechanical and thermal properties of PS was investigated via impact, tensile, and thermal measurements
A slight maximum ductility is reached for a second quenching from 110◦C until
Summary
In a previous study [1], the effect of different heat treatments on the mechanical properties of polycarbonate (PC) was investigated. When the stresses are related to external loads, they are superimposed to tensile residual stresses so that in these conditions the plastic yielding will begin at a lower load Polymers such as polystyrene (PS) and poly (methyl methacrylate) (PMMA) typically fracture after being stretched to a few percent strains. Hornberger and DeVries [16] using various techniques indicate that quenching of PS in ice water and allowing the samples to achieve thermal equilibrium at room temperature, results in surface residual stresses of approximately 15 MPa. Narkis et al [17] have measured the state of the residual stresses on heat distortion temperature (HDT) of various styrene copolymers. Siegmann et al [10] investigated the effects of the residual stresses on crazing and softening behaviours of PS and PMMA quenched from various temperatures into iced water Both PS and PMMA showed a decrease in heat deflection temperatures as the magnitude of the residual stresses increased. This paper describes a method to produce favorable RS in polystyrene by optimizing the process of thermal quenching and the subsequent effects on mechanical, thermal, and thermophysical properties
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