Improvement of Structure and Properties of Polypropylene/Poly(ethylene-co-propylene) In-reactor Alloy by Modifying the Cocatalyst

Summary : A series of polypropylene/poly(ethylene-co-propylene) in-reactor alloy were synthesized by a TiCl₄/MgCl₂/SiO₂/diester type Ziegler-Natta catalyst, using triethylaluminium (TEA), triisobutylaluminium (TIBA) or TEA/TIBA mixtures of different molar ratio as cocatalyst. Mechanical properties of the alloy are strongly influenced by the cocatalyst. Toughness-stiffness balance of the alloy synthesized using a 50/50 TEA/TIBA mixture as cocatalyst is much better than that of the alloy based on pure TEA cocatalyst. Changes in copolymer chain structure and composition distribution are thought to be the main reason for this improvement of properties.