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Indexed by:期刊论文

Date of Publication:2017-07-01

Journal:POLYMER TESTING

Included Journals:SCIE、EI、Scopus

Volume:60

Page Number:260-265

ISSN No.:0142-9418

Key Words:Plateau modulus; Isotactic polypropylene; Ultra-high molecular weight; Polydisperse

Abstract: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.