Rubber-like tensile behaviour of yielded high-impact polystyrene

The tensile stress-strain properties of yielded high-impact polystyrene (HIPS) have been investigated at room temperature. Two HIPS samples were considered, having different rubber-phase particle sizes and morphologies. Specimens have been subjected to two subsequent tensile test runs, the first one to produce the yielded matter and the second one to test it. Different amounts of yielded matter content in the specimens and different strain rates for yielded matter production were examined by varying the test conditions in the first run. Yielded HIPS exhibits a rubber elastic stress-strain behaviour, which has been interpreted by assuming that a rubber-like material, proportional in amount to the plastic deformation, is present in the specimens as a consequence of the yielding process.