Effect of β‐nucleating agents on structure and mechanical properties of dynamic crosslinked ethylene‐octene random copolymer/polypropylene and ethylene‐octene block copolymer/polypropylene blends

Abstract

Ethylene‐octene block copolymer (OBC) and ethylene‐octene random copolymer (ORC) replacing EPDM as rubber phase in EPDM/PP vulcanizates with and without β‐nucleating agent are prepared in this study. The effect of β‐nucleating agent and different chain structure of ethylene‐octene copolymers on dynamic crosslinked ORC/PP and OBC/OBC blends are studied. The dynamic crosslinked ORC/PP and OBC/PP result in noticeable phase separation between the elastomer phase and PP phase, as indicated by the presence of two crystallization peaks. β‐crystals was proved by the Wide‐Angle X‐ray Diffraction result. β‐nucleating agent finer the crystals of ORC/PP and OBC/PP blends, results in better mechanical property than blends without β‐nucleating agent. Dynamic mechanical analysis indicates that the α transition and β transition in ORC/PP tend to exhibit broad peaks, suggesting improved compatibility between ORC and PP. However, due to the effect of β‐nucleating agent, the α transition and β transition of β‐ORC/PP are distinctly separated. The β‐OBC/PP shows higher elongation than β‐ORC/PP. The interfacial interaction between ORC and PP is better than OBC and PP, evidenced by the elongation at break of crosslinked OBC exceeds that of crosslinked ORC by 176%, but β‐OBC/PP shows only a 124% increase in elongation at break over β‐ORC/PP.