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Keywords:

  • polyethylene nanocomposite;
  • nonisothermal crystallizatin kinetics;
  • aspect ratio;
  • multiwall carbon nanotubes;
  • activation energy;
  • secondary crystallization

Abstract

In this article, the effect of aspect ratio and chemical modification of multiwall carbon nanotubes (MWCNT) on the nonisothermal crystallization kinetics of LDPE/MWCNT nanocomposites was studied. Nine different samples were prepared using different MWCNT to study both effects. The cooling rate (R) was varied in the range 2–10°C/min. In this article, the effect of CNT loading, surface modification, and aspect ratio were studied. For the same MWCNT concentration, aspect ratio and [BOND]COOH modification had weak influence on both the peak crystallization temperature and the crystallization onset temperature. However, the crystallization onset temperature was significantly affected by the amount of MWCNT. The rate parameters in the modified Avrami method and Mo method [F(T)] of analyses show a very good fit of data. The Vyazovkin and Sbirrazzuoli method of analysis, which is based on Hoffman–Lauritzen theory for secondary crystallization, was also used. Temperature dependency of activation energy was obtained for 30–75% relative crystallinity of the produced nanocomposites. Activation energy based on calculations of Hoffman-Lauritzen theory showed a decrease with the increase in the concentration of MWCNT and crystallization temperature. A proposed model of the form E = a exp (-bXT) which relates the activation energy, E, to relative crystallinity, X, and crystallization temperature, T, was able to fit the whole set of data. Incorporation of MWCNT in nanocomposites lowers the activation energy; hence enhances the initial crystallization process as suggested by the different methods of data analyses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011