Structures and Properties of Isotactic Polypropylene/Polybutene-1 In-reactor Alloys

The performance of materials is closely related to the composition, component distribution and molecular chain structure. Therefore, it is vital to analyze the relationship between chain structure and performance of alloys with multiple components. Two novel isotactic polypropylene/polybutene-1 in-reactor alloys (iPP/iPB) synthesized by sequential two-stage polymerization were fractionated by the temperature rising elution fractionation at a temperature ranging from -30 degrees C to 140 degrees C. The chain microstructure and sequences distribution, crystallization behavior, molecular weight (M-w) and molecular weight distribution (M-w/M-n) of fractions were characterized by C-13 NMR, FTIR, DSC, GPC. The results showed that iPP/iPB alloys were mainly composed of five components, including the high isotactic polybutene-1(iPB) as the main component, a small amount of poly ((butene-1)-block-propylene) block copolymer (PB-b-PP), isotactic polypropylene (iPP), etc. With the increase of elution temperatures, the length of PP blocks in the PB-b-PP components gradually inereic-ed, while that of PB blocks gradually decreased. At the same elution temperature, Alloy B possessed longer PP block in copolymer fractions and exhibited more perfect PP crystal. Alloy B containing higher iPB and PB-b-PP components showed higher tensile strength, flexural strength, excellent impact resistance, higher Vicat softening temperature and faster crystal transformation rate.