Temperature rising elution fractionation and fraction compositional analysis of Polybutene-1/Polypropylene in-reactor alloys

A series of isotactic polybutene-1/polypropylene (PB/PP) in-reactor alloys were prepared by Ziegler-Natta catalyst using sequential two-stage polymerization technology. Temperature rising elution fractionation (TREF) combining with DSC, GPC and ¹³C-NMR were used to analyze the compositional heterogeneity of the resulting PB/PP alloys. Fractions in the PB/PP alloys, including isotactic polybutene-1, isotactic polypropylene, atactic polybutene-1, a series of copolymers with different length of PB segments, PP segments, and poly(propylene-co-(butene-1)) segments, were isolated for the first time by TREF whereby the chain structure and sequence distribution of these fractions were characterized. A possible mechanism was proposed to explain the fraction formation in this sequential two-stage polymerization technology. The mechanical properties and polymorphic transition of the PB/PP alloys were also studied and correlated with the fraction structure and distribution.