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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.
Rouabah et al. (2012) studied this question.