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论文类型：期刊论文

发表时间：2017-07-01

发表刊物：POLYMER TESTING

收录刊物：SCIE、EI、Scopus

卷号：60

页面范围：260-265

ISSN号：0142-9418

关键字：Plateau modulus; Isotactic polypropylene; Ultra-high molecular weight; Polydisperse

摘要：Ziegler-Natta catalysis was employed to prepare isotactic polypropylenes (iPPs) with various viscosity average molecular weight Mn, where Mn exceeds 1 000 000 g/mol. The viscoelastic properties of the synthesized ultra-high molecular weight iPPs (UHMWiPPs) were investigated by means of oscillatory rheometry. Due to the polydispersity of these polymers that derived from multi-sites catalyst, the UHMWiPPs rheological parameters, including Arrhenius activation energy Ea, plateau modulus G(N)(0), as well as the molecular weight between entanglements Me, were compared with that of the reported monodisperse iPPs. We critically evaluated the typical methods for the experimental determination of G(N)(0), for polydisperse UHMWiPP5 with linear architecture and concluded that the preferred method for UHMWiPP was the extrapolation integration method, which gave an average value of G(N)(0) = (4.9 +/- 0.3) x 10(5) Pa and M-e = (6300 +/- 400) gimol. The polydipersity was proved to be acceptable for the UHMWiPP system in this research. However, the rheological measurements should be operated with caution because the temperature window was very narrow and the UHMWiPPs were extremely sensitive to thermal oxidative degradation during the tests. (C) 2017 Elsevier Ltd. All rights reserved.