In situ formation of PE-EPR core-shell rubber particles in polypropylene matrix by melt blending: Effect of PE chain structure and viscosity

Twenty types of polyethylene (PE) including high density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) with various viscosity were used to study the in-situ formation of PE- ethylene propylene rubber (EPR) core-shell rubber particles (CSRP) in polypropylene (PP) matrix by melt blending. The results show that PE and EPR cannot form CSRP if PE melt flow index (MFI) is lower than about 0.3 g/10 min. As a result, the impact fracture of PP/PE/EPR composite is brittle. If PE MFI is higher than 0.3 g/10 min, PE and EPR can form CSRP, leading to the ductile impact fracture of PP/PE/EPR composite. Interestingly, upper limit content of PE for the formation of CSRP depends on the type and viscosity of PE. For HDPE, upper limit content of PE tends to increase with the increase of its MFI, whereas it drops considerably for LLDPE. Understanding these relationships provides insights into optimizing the selection of core types and viscosity for enhancing the mechanical properties of polymer composites with core-shell structure. This may potentially guide the development of cost-effective and high-performance polymer composites.