There are several chemical methods available today to prepare high melt strength PP (HMS-PP) products containing a small amount of LCB structures. However, they are quite expensive, the processes either requiring multiple reaction steps or/and forming a complicate mixture of branch structures. This paper discusses a new efficient and economic method involving the 4th generation MgCl2-supported TiCl4 catalyst and slurry polymerization process, followed with the extruding/pelleting procedure. This direct-polymerization process is centered on an asymmetric diene comonomer p-(3-butenyl)styrene (BSt) that can be randomly incorporated in PP chain with a mono-enchainment fashion by isospecific Ziegler-Natta catalyst. The predominate 1,2-insertion of a-olefin moiety in BSt comonomer forms a linear PP-co-BSt copolymer (granules), with few pendant styrene moieties randomly distributed along the polymer chain. The resulting PP-co-BSt copolymers were melt-processed using common PP extruding and pelletizing procedure at ~200 oC to produce pelletized products. Under this elevated temperature, the molten PP-co-BSt copolymer effectively engages the in-situ cycloaddition reaction between pendant styrene units to form PP branches with long branch length. The branch density is controlled by BSt content in the copolymer and the degree of thermal-induced coupling reaction. The resulting LCB-PP polymers (pellets) are completely melt-processible and exhibiting high melt strength under elongation flows.

Direct synthesis of high melt-strength polypropylene using the 4th generation heterogeneous Ziegler-Natta catalyst and slurry production process

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.