Influence of cocatalyst on the structure and properties of polypropylene/poly (ethylene‐ co ‐propylene) in‐reactor alloys prepared by MgCl 2 /TiCl 4 /diester type Ziegler‐Natta catalyst

In this work, a series of polypropylene/poly(ethylene‐ co ‐propylene) (iPP/EPR) in‐reactor alloys were prepared by MgCl 2 /TiCl 4 /diester type Ziegler‐Natta catalyst with triethylaluminium/triisobutylaluminium (TEA/TIBA) mixture as cocatalyst. The influence of cocatalyst and external electron donor, e.g., diphenyldimethoxysilane (DDS) or dicyclopentyldimethoxysilane ( D ‐donor), on the structure and mechanical properties of iPP/EPR in‐reactor alloys were studied and discussed. According to the characterization results, PP/EPR was mainly composed of random poly(ethylene‐ co ‐propylene), segmented poly(ethylene‐ co ‐propylene), and high isotactic PP. Using TEA/TIBA mixture as cocatalyst and DDS as external electron donor, as TEA/TIBA ratio increased, the impact strength of iPP/EPR in‐reactor alloys had an increasing trend. Using TEA/TIBA mixture as cocatalyst and D ‐donor as external electron donor, the impact strength of iPP/EPR in‐reactor alloy were dramatically improved. In this case, the iPP/EPR in‐reactor alloy prepared at TEA: TIBA = 4 : 1 was the toughest. The influence of cocatalyst and external electron donor on the flexural modulus and flexural strength could be ignored. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011