Fracture behaviour of β‐polypropylene as a function of processing conditions

The commercial grade of isotactic polypropylene (iPP) homopolymer (Mosten 58.412) was doped with different amount of β‐nucleant (NJ Star NU‐100). The fracture behavior of the β‐iPP was examined on injection‐ and compression moulded specimens under dynamic load. The fracture toughness K_Id and J_Id, respectively, were used to describe the fracture behavior. The influence of processing conditions (the mould temperature and injection velocity) and the distance from the gate were also taken into the consideration. Structural changes during processing were characterized by DSC analysis. It was found that: (i) the amount of 0.03% of β‐nucleant gives the highest toughness (ii) the toughness of the β‐iPP depends on the distance from the moulding gate and on the processing conditions (iii) the degree of crystallinity correlates with the fracture parameters.