Blending Behavior of High-Degree Long-Chain-Branched Polypropylene Prepared by Ziegler-Natta Catalysis with Common Polypropylene

Two high-degree long-chain-branched polypropylenes (LCB-PPs), one being homopolymer and the other random copolymer (with a minor composition of ethylene), were prepared in industrial trials by Ziegler-Natta catalysis with the omega-alkenylmethyldichlorosilane-mediated successive polymerization-hydrolysis chemistry. They were then melt-blended with a common PP homopolymer and random copolymer resins, respectively. The compositional ratios (weight percentage ratio, LCB-PP/common PP) in the blends were controlled in a broad rang; from 20/80 to 80/20, each increased/decreased by 10%. The results indicate that the LCB-PP is well miscible with the common PP. From the perspective of LCB-PP, the blends diversify their properties, extending the product range to higher melt flow rates. On the other hand, the blends bring the best-fit LCB structure to common PP, boosting their melt strength and melt processability involving extensional flow in a highly controlled manner. However, exceptions exist to defy the composition dependency. For the homopolymer blends, their Young's moduli are noticeably higher than the individual LCB-PP and common PP constituents. Moreover, both the homopolymer and random copolymer blends were measured at higher crystallization temperatures (T-c) than their individual components. The nucleation effect of the LCB structure is deemed to play an exceptional role in the LCB-PP/common PP blends.

Automated summary

Two high-degree long-chain-branched polypropylenes were prepared and melt-blended with common PP, diversifying properties and extending product range. Exceptions exist challenging composition dependency, with LCB structure's nucleation effect playing a significant role in the blends.