Mechanical & Materials Engineering, Department of
Concomitant Crystallization in Propylene/Ethylene Random Copolymer with Strong Flow at Elevated Temperatures
Lirong Zheng: 0000-0001-6803-5048
Lucia Fernandez-Ballester: 0000-0001-6956-5104
Gerrit W. M. Peters: 0000-0001-7208-5128
Zhe Ma: 0000-0003-2458-4197
Date of this Version
Published in Industrial & Engineering Chemistry Research 57 (2018), pp 6870−6877.
Flow-induced crystallization of α- and γ-phases was studied for a propylene/ethylene random copolymer with 3.4 mol % ethylene at two high temperatures of 132 and 142 °C by combining a pressure-driven slit flow device with real-time synchrotron wide-angle X-ray diffraction. At 132 °C, it was found that both α- and γ-phases were generated at shear stresses ranging from 0.091 to 0.110 MPa and that the γ-phase always appeared later than the α-phase. However, for 142 °C and the same stresses, only the α-phase formed. Only upon cooling the partially crystallized copolymer did the γ-phase emerge. The lack of γ-crystals obtained at 142 °C is opposite to the behavior reported for quiescent crystallization under pressure, for which increasing temperature results in more and even pure γ-crystals. In the current study, the absence of γ-phase at 142 °C is tentatively associated with lack of epitaxial nucleation on α-lamellae and to relatively low growth rate of γ-crystals.
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