期刊
EUROPEAN POLYMER JOURNAL
卷 49, 期 6, 页码 1577-1590出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.eurpolymj.2013.02.002
关键词
Polypropylene; Copolymer; Crystallization; Nucleating agent
资金
- European Union (European Social Fund - ESF)
- Greek national funds through the Operational Program Education and Lifelong Learning of the National Strategic Reference Framework (NSRF) - Research Funding Program: Heracleitus II. Investing in knowledge society through the European Social Fund
The different crystallization behavior of two propylene ethylene random copolymers, (PPR- and PP-RCT), one of which (PP-RCT) contains a beta-nucleating agent is investigated in the present paper. Isothermal and non-isothermal crystallization behavior was thoroughly studied. The subsequent melting behavior after isothermal crystallization was studied by means of standard, and Step-Scan DSC. The equilibrium melting point of alpha crystals determined using the Hoffman Weeks extrapolation was 11.8 degrees C higher than that for beta crystals. The Lauritzen-Hoffman theory was applied and the nucleation constant K-g and the surface free energy sigma(e) was calculated. From the isothermal experiments it was concluded that the nucleating agent increased drastically the crystallization rate of the copolymer, also promoting the generation of beta crystals. On cooling PP-RCT crystallized at about 8 degrees C higher temperatures than PP-R. The non-isothermal crystallization of the materials was examined and for the kinetics analysis the Avrami, Ozawa and Mo models were elaborated. Nucleation activity was calculated with the use of Dobreva's method. The effective activation energy was calculated for both polymers according to the iso-conversional method of Friedman and lower values resulted as expected in case of the PP copolymer with nucleating agent. (C) 2013 Elsevier Ltd. All rights reserved.
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