Compatibilization of Post‐Consumer Recycled Polypropylene/Polyethylene Binary Blends

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ABSTRACTThis work investigates the compatibilization of post‐consumer recycled binary blends of polypropylene/polyethylene (PP/PE), with either high‐density PE (HDPE) or linear low‐density PE (LLDPE). Ethylene‐octene elastomer copolymers from the olefin block copolymers (OBC) family, Dow's INFUSE 9107 and INFUSE 9507, were used as compatibilizers at 4, 6, and 8 wt%. Two different recycled PP/PE blends were used: a 50/50 by weight PP/HDPE white blend (0 W), and a black blend (0B) comprising 85/15 PP/LLDPE by weight. The mechanical properties, thermal properties, and morphology of these injection‐moldable blends indicate that compatibilization took place. Elongation at break and tensile impact strength increased with compatibilizer content, especially with INFUSE 9107. For instance, the impact strength of 0 W increased almost three‐fold with 8 wt% OBC, while that of 0B was doubled with 6 wt% OBC. The tensile strain at break increased up to six‐fold with 8 wt% OBC, reaching 360% and 180% for the white and black blends, respectively. Elastic Moduli decrease to some extent, but remain within the range of applicability of PP‐based compounds. The melt flow index (MFI) values, above 20 g/10 min for 0 W and 7–8 g/10 min for 0B, allow for injection molding of these blends. Moreover, a two‐phased morphology became less apparent, the improved compatibility being driven by the lower interfacial surface energy of the blend and more efficient stress transfer between the phases. INFUSE 9107 achieved better impact strength and elongation results, mainly in the white blends, and this is explained by the better compatibility, its localization at the interface, and the lower crystallinity of the compatibilized blend.