The way a glassy polymer behaves depends crucially on how it has been deformed during processing. Common polymer processing operations such as injection-moulding and extrusion induce deformations in polymer melts, and result in different degrees of frozen-in orientation.
We have studied the effects of different degrees of orientation on a few monodisperse grades of polystyrene, by deforming bars over a range of temperatures and by allowing different degrees of relaxation to occur. The materials are then retested under identical conditions, in the glassy state, and the deformation is carefully measured. This data is important for the development of constitutive models able to capture the effects of processing on properties.
The stress-strain behaviour of bars of polymer pre-deformed by the same amount, but at different temperatures
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