Heterogeneity of crystalline structure of injection-moulded and drawn isotactic polypropylene studied by DSC

Differential scanning calorimetry (DSC) was used to characterize crystallin e structure of injection-moulded specimens of isotactic polypropylene and c orresponding materials prepared by solid-state drawing at various temperatu res. It was shown that the DSC can assess the differences between individua l specimens and structural gradients and heterogeneities within one typical test piece. In particular, relative proportions of the crystalline a and b eta modifications in different locations of an injection-moulded specimen a nd structural transformation in the neck shoulder could be established. Var iations of the crystalline structure along the edge of drawn specimens were interpreted as a record of temperature and stress fluctuations in the prop agating neck shoulder.