Periodic Switching of Monomer Additions for Controlling the Compositions and Microstructures of Segmented and Random Ethylene-Propylene Copolymers in Polypropylene in-Reactor Alloys

Abstract

International audienceThis work aims at shading fundamental insights into mechanisms that dictate the composition and microstructure of polypropylene/poly(ethylene-co-propylene) (PP/EPR) in-reactor alloys produced by the multizone circulating reactor (MZCR) technology, a novel one for polyolefin production. For this purpose, this technology is simulated by a batch process with periodic switching of monomer additions. An increase in the switch frequency leads to a decrease in the fraction of ethylene/propylene random (amorphous) copolymers denoted as EPR and an increase in the fraction and the length of PP segments of ethylene/propylene segmented (partially crystalline) copolymers denoted as EPS. Concomitantly, the size of the dispersed phase domains (EPR) decreases, and its size distribution becomes more uniform as a result of the decrease in the fraction of the EPR and the increase in that of the EPS which acts as a compatibilizer for PP/EPR in-reactor blends. Mechanical properties of the PP/EPR in-reactor blends are also discussed

An atmosphere‐switching polymerization process: A novel strategy to advanced polyolefin materials

“…Even in this latter case, these shells are so thin that segregation of different polymer phases is minimized. As expected, when the ASPP was used to prepare IPC in a previous work, 16 the size of the dispersed EPR phase domains decreased with increasing switching frequency (herein number of cycles). Furthermore, a large amount of EPS could be formed, owing to the fact that polymer particles were exposed to atmosphere "propylene" and atmosphere "ethylene-propylene" time and again.…”

“…It relies on periodic switching of monomers which can improve the compatibility between EPR and PP by controlling the molecular structures of the EPS. 16,17 Unlike a conventional TSPP in which the homopolymerization of propylene and the copolymerization of ethylene and propylene take place successively and only once, in the case of ASPP they proceed periodically and many times.…”

Role of crystalline ethylene‐propylene copolymer on mechanical properties of impact polypropylene copolymer

“…[4][5][6][7] Among several techniques, in situ copolymerization with ethylene by adding a gas-phase reactor in the production line is an effective one which has been used on an industrial scale to obtain highimpact resistant PP or impact PP copolymer (IPC). 13,14 When IPC is melted, a unique heterophasic morphology is formed. EP random copolymer (EPR) is a major component which is responsible for the toughness improvement.…”

Phase‐separation of heterophasic polymer in solution: A model case of impact‐resistant polypropylene copolymer

“…Referring to works published by Tien et al . their sEP was obtained by fractionation, C7‐soluble fraction, which corresponds to the cEP in this present work . However, in strictly defining, sEP should be referred to the copolymers with the segments of long sequences of either ethylene (E) or propylene (P) units, or both types of segments in the chain.…”

“…The periodic‐switching technique was exploited to manipulate the EPR and sEP contents. The results showed that the droplet size of the EPR dispersed phase decreased as the content of the sEP increased . This suggested the role of the sEP on the improvement of the interfacial adhesion between hPP and EPR phases, and this similar finding also has been reported in several works .…”