Hydroxyl-Functionalized Polypropylene Induces Melt Strain Hardening in Isotactic Polypropylene Melt and Influences Its Foaming

The paper addresses the development of uniform functionalized polypropylenes and discusses a peculiar behavior of polymer blends containing isotactic polypropylene (iPP) and low molecular weight linear propylene/10-undecene-1-ol copolymers (PP–OH) under complex flows. We present a remarkable finding: a small addition of the PPOH to the standard iPP melt induces substantial melt strain hardening under extensional deformation. This unconventional approach enhances the general understanding that the strength and foamability of iPP melts can only be improved by adding long-chain branched polypropylenes or extremely long polyolefin chains. By leveraging this phenomenon, we produce a range of PP foams whose characteristics are comparable to conventional foams, with slightly lower performance, while maintaining the added benefit of polarity. Our findings present alternative opportunities for tailoring the rheological properties of iPP and expanding its range of applications.