Crystal nucleation in polypropylene injection‐moulding resins containing fibrous fillers

Injection mouldings contain residual stress and molecular orientation and both are influential in determining properties. When a fibrous filler is present the magnitude and distribution of residual stress and molecular orientation are modified and, with semi crystalline polymer matrices, the crystal morphology is also modified. This subject has been studied recently by Misra et al.1 and their views are discussed here. We propose that some of the effects they attribute to residual stress are better explained with reference to molecular orientation.