The tensile stress-strain behaviour of polystyrene in inert and gaseous environments

Abstract

For the first time the intrinsic tensile stress-strain behaviour of polystyrene was measured in an inert atmosphere (He) from 77 to 350 K. The intrinsic tensile strength decreases monotonically with increasing temperature with completely brittle behaviour below 231 K and crazing without shear flow at higher temperatures. The behaviour in N₂, Ar, CH₄, CO₂, H₂S, and N₂O was observed with the relative pressure being the important parameter. The softening depended on the square root of the relative pressure. A calculation was made of the concentration of absorbed gas to produce a given amount of softening. The question of why polystyrene is a brittle solid and thus crazes instead of shear flows is discussed.