Investigating Effects of Using Mixtures of Two External Electron Donors on Microstructure and Properties of Polypropylene/Poly(ethylene‐co‐propylene) in‐Reactor Blends Based on Ziegler–Natta Catalyst

Abstract

Novel results on using mixtures of two external electron donors “phenyltriethoxysilane (donor A)” and “cyclohexylmethyldimethoxysilane (donor C)” in the synthesis of polypropylene/poly (ethylene‐co‐propylene) in‐reactor blends were presented. Thermal gradient elution fractionation (TGEF) was carried out to separate crystallizable copolymer fractions from the blends. FTIR, DSC, DMTA, and SEM were used to analyze the microstructure of the blends and separated fractions. Although using donor A as pure decreased the catalyst activity and molecular weight, using “donor A” in combination with donor C had a synergistic effect on the molecular weight of polypropylene homopolymers and the blends. The glass transition temperature (Tg) of the blend rubbery phase was the lowest in the case of the blend based on pure donor A because of formation of higher sequences of polyethylene and the Tg increased with increasing donor C concentration. PP–PE copolymer concentration and impact strength were found to be higher in the case of the blend based on donor ratio of A/C: 75/25 than other blends.

Polypropylene with high melt flow rate and high isotacticity prepared by phosphate‐mixed external donors

“…The molecular weight of polypropylene prepared by alkoxysilane was high and its molecular weight distribution ranged from 3 to 5, which led the polypropylene to maintaining good mechanical properties but low flowability. The mixture of different alkoxysilane compounds was also used as external donor to study its effect on polypropylene . Peiyuan Li investigated the influence of complex alkoxysilane external donor (diphenyldimethoxysilane/dicyclopentyldimethoxysilane) in MgCl 2 ‐supported Ziegler–Natta catalyst of propylene polymerization, which produced polypropylene with high molecular weight and its molecular weight distribution was 5.6.…”