Supernucleation and crystallization regime change provoked by MWNT addition to poly(ε-caprolactone)

被引:95
作者
Trujillo, Mariselis [1 ]
Luisa Arnal, Maria [1 ]
Mueller, Alejandro J. [1 ]
Mujica, Mayra A. [2 ]
Urbina de Navarro, Caribay [2 ]
Ruelle, Benoit [3 ]
Dubois, Philippe [3 ]
机构
[1] Univ Simon Bolivar, Grp Polimeros USB, Dept Ciencia Mat & Mecan, Caracas 1080A, Venezuela
[2] Cent Univ Venezuela, Fac Ciencias, Ctr Microscopia Elect, Caracas, Venezuela
[3] Univ Mons UMONS, Serv Mat Polymeres & Composites SMPC, Ctr Res & Innovat Mat & Polymers CIRMAP, B-7000 Mons, Belgium
关键词
Supernucleation; Carbon nanotubes; Polycaprolactone; WALLED-CARBON-NANOTUBES; DIFFERENTIAL SCANNING CALORIMETRY; POLYPROPYLENE ALPHA-PHASE; IN-SITU POLYMERIZATION; NONISOTHERMAL CRYSTALLIZATION; ISOTHERMAL CRYSTALLIZATION; SELF-NUCLEATION; THERMAL FRACTIONATION; EPSILON-CAPROLACTONE; POLY(ETHYLENE OXIDE);
D O I
10.1016/j.polymer.2011.12.028
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
In this work, the nucleation and crystallization behavior of melt mixed PCL/CNT nanocomposites has been studied. The mixtures of PCL and pristine MWNTs were prepared by extrusion with different nanofiller contents: 0.3, 0.5, 0.7, 1 and 3%. Standard DSC measurements demonstrated pronounced nucleation effects as well as increases in PCL crystallinity. The nucleation effect saturates at only 0.5% (a value much lower than those previously reported in the literature for similar nanocomposites) indicating that the dispersions obtained were excellent. This was corroborated by both TEM observations and by the determination of a very low dielectric percolation threshold (i.e., 0.3%). In self-nucleation experiments, supernucleation effects were obtained up to a maximum of approximately 200% efficiency. This is the first time that supernucleation effects of this order have been reported for PCL filled with untreated MWNTs, a result that we attribute to the excellent dispersion achieved. Isothermal crystallization experiments performed by DSC showed an increase in the crystallization kinetics of PCL with increases in MWNT content as a consequence of the supernucleation effect. The Avrami equation successfully described the overall crystallization kinetics and while neat PCL exhibited Avrami indexes close to 3, indicating that instantaneously nucleated spherulites were formed, the nanocomposite yielded mostly Avrami index values close to 2, as expected for axialites instantaneously nucleated on the surface of the MWNTs. Remarkably, the temperature dependence of the overall crystallization rate exhibited a dramatic change with MWNT content. This novel effect was described as a crystallization regime change (i.e., from Regime II to Regime Ill) induced by the presence of the MWNTs in terms of the Lauritzen and Hoffman theory. (C) 2012 Elsevier Ltd. All rights reserved.
引用
收藏
页码:832 / 841
页数:10
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