Processing of polyolefin blends

Abstract

Abstract The morphology of binary and ternary polyolefin blends of polypropylene (PP), ethylene‐propylene‐diene terpolymer (EPDM) and polyethylene (PE) following processing by injection and compression molding has been examined by optical and scanning electron microscopy. Internal surfaces were generated by low temperature fracture and etching with cyclohexane. In binary blends, droplets of EPDM are elongated in the flow direction within 400μm of the mold surface in injection molding, yielding a skin region which is distinct from an isotropic core containing spherical EPDM inclusions. Spherical droplets of EPDM or PE in binary blends with PP increase in size with increasing compression molding time. In ternary blends, spherical inclusions containing both EPDM and PE are dispersed in PP. With increasing compression molding time, EPDM separates from PE and concentrates at the outer edges of the PE inclusion, effectively isolating PE from the PP matrix.