Abstract
The mechanical properties of PVC sheets can be modified substantially by both uniaxial and biaxial stretching of the material above its glass transition temperature. Previous experimental studies have established a clear pattern in the relationship between tensile properties of oriented PVC products and imposed strains. Several mathematical models have been scrutinised to assess whether the established pattern of behaviour can be modelled and predicted. Of these, ‘the filament theory’, proposed by Turner, emerged as the best candidate. The filament theory has been refined and developed further into ‘the composite model'. In its present form it gives a good correlation between predicted and measured yield stress values of oriented rigid PVC sheets and it is also capable of predicting the ‘established pattern' of property dependence upon imposed strain.