Upcycling of polypropylene—the influence of polyethylene impurities

Abstract

Long chain branching (LCB)—a well‐known industrial process—is shown as an innovative tool for the treatment of PP post‐consumer waste. The introduction of LCB by reactive extrusion does not only compensate the degradation during product life (e.g., thermally and UV‐induced chain scission), it also improves the melt properties (e.g., melt strength, strain hardening). Thus, not only a re‐cycling process, even a real “up‐cycling” can be achieved. Compared with virgin material, PP from post‐consumer waste contains impurities like other polyolefines (PE‐HD, PE‐LD, PE‐LLD, copolymers), the total removal is economically not viable. Hence, the focus of this work was the influence of PE‐HD on the LCB formation of PP. Based on model mixtures with virgin PP and 10% PE‐HD, it is shown that PE‐HD influences the mechanical properties and gel content of the chemically modified blend but has no detrimental effect on the improved melt properties. POLYM. ENG. SCI., 57:1374–1381, 2017. © 2017 Society of Plastics Engineers