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

Ethylene-octene block copolymer (OBC) and ethylene-octene random copolymer (ORC) replacing EPDM as rubber phase in EPDM/PP vulcanizates with and without beta-nucleating agent are prepared in this study. The effect of beta-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. beta-crystals was proved by the Wide-Angle X-ray Diffraction result. beta-nucleating agent finer the crystals of ORC/PP and OBC/PP blends, results in better mechanical property than blends without beta-nucleating agent. Dynamic mechanical analysis indicates that the alpha transition and beta transition in ORC/PP tend to exhibit broad peaks, suggesting improved compatibility between ORC and PP. However, due to the effect of beta-nucleating agent, the alpha transition and beta transition of beta-ORC/PP are distinctly separated. The beta-OBC/PP shows higher elongation than beta-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 beta-OBC/PP shows only a 124% increase in elongation at break over beta-ORC/PP.