Tailoring End-Use Properties of Polypropylene through a Combination of Specific Nucleation and Long-Chain Branching

The present study presents an assessment of the interrelations between long-chain branching, specific nucleation, and end-use properties of polypropylene blends: blends of linear polypropylene (L-PP) and long-chain branched polypropylene (LCB-PP) modified by a specific β-nucleating agent (NA). Specimens with various LCB-PP compositions with and without NA were prepared under complex flow fields by injection molding. Wide-angle X-ray scattering was employed to capture the X-ray patterns of both the skin and core of the specimens, determining the overall crystallinity and amounts of individual polymorphs. The increasing content of LCB-PP and γ-phase, at the same time, in the blends is reflected in both increasing crystallinity and improved mechanical properties, namely, yield stress and Young’s modulus. On the other hand, the composition of the blends had no significant effect on the impact strength, except for nucleated L-PP. It has been demonstrated that adding a relatively small amount of LCB-PP is sufficient to modify the mechanical properties of linear polypropylene. Even a very small amount of LCB-PP in the L-PP suppressed the effectiveness of NA.