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Tian Zhou, PhD candidate, published a paper entitled "Effects of Switching Frequency of a Periodic Switching Polymerization Process on the Microstructures of Ethylene–Propylene Copolymers in PP/Poly(e

Editor:admin  Date:2012-02-28 16:35:42   Hits:2386

      我组博士生田洲撰写的论文《Effects of Switching Frequency of a Periodic Switching Polymerization Process on the Microstructures of Ethylene-Propylene Copolymers in Polypropylene/Poly(ethylene-co-propylene) in-Reactor Alloys》在化学工程国际权威期刊Industrial & Engineering Chemistry Research上发表。该工作提出了基于Ziegler-Natta催化剂的周期性气氛切换聚合机理,研究切换频率对乙丙共聚物微结构的影响。采用溶剂分级与13C NMR, GPC, SSA以及数学去卷积相结合的方法细致表征了抗冲聚丙烯共聚物的链结构,为调控聚丙烯多相共聚物的结构与性能提供依据。

ABSTRACT: This work deals with the effects of the switching frequency of a periodic switching polymerization process (PSPP) with a Ti-based Ziegler–Natta catalyst on the microstructures of ethylene–propylene copolymers in polypropylene/poly(ethylene-co-propylene) (PP/EPR) in-reactor alloys. The compositions and structures of PP/EPR in-reactor alloys are investigated by solvent fractionation, 13C NMR, gel permeation chromatography (GPC), successive self-nucleation and annealing (SSA) by differential scanning calorimetry (DSC), and statistical deconvolution. The sequence distributions of ethylene–propylene random copolymer (EPR) and ethylene–propylene segmented copolymer (EPS) are successfully deconvoluted from the 13C NMR spectra of fractionated samples. The results are consistent with the expected effects of the switching frequency on the composition and microstructures of EPR and EPS. A higher switching frequency between the homopolymerization of propylene and the copolymerization of ethylene and propylene increases not only the ratio between the EPS and EPR but also the fractions of long PP segments and long PE segments in the EPS. The effect of the mean residence time on the composition and microstructure of PP/EPR in reactor alloys is also discussed.