Isothermal and non-isothermal crystallization kinetics of composites of poly(propylene) and MWCNTs

The isothermal and non-isothermal crystallization behaviour of composites of a poly(propylene) (PP) and multi-walled carbon nanotubes (MWCNTs) were investigated using Differential Scanning Calorimetry (DSC). An Avrami analysis was used to study the isothermal crystallization kinetics of unfilled PP and composites of PP with MWCNT loadings up to 2 (w/w). The value of the Avrami exponent (n) was greater than 2 for all samples, confirming the primary stage of crystal growth is a three-dimensional phenomenon. The activation energy (ΔE), determined using an Arrhenius type expression, for the isothermal crystallization of PP increased from 87 kJ for unfilled PP to 228 kJ on incorporation of 2 (w/w) MWCNTs to PP. An attempt was made to model the non-isothermal crystallization kinetics of composites of PP and MWCNTs using a range of mathematical models, including the Jeziorny extended Avrami equation, Ozawa equation, Cazé and Chuah average Avrami exponents, and a combined Avrami/Ozawa approach. The Jeziorny extended Avrami approach confirmed that the non-isothermal crystallization of MWCNT filled PP is clearly a two-stage process. Fitting of the Ozawa model was shown to be not valid and both the Cazé and Chuah average Avrami approaches were ineffective as neither took in to account the effects of secondary crystallization. Only the combined Avrami/Ozawa method successfully modelled the two-stage crystallization of composites of PP and MWCNTs. The activation energy (ΔE) for the non-isothermal crystallization of PP on addition of MWCNTs increased with increasing MWCNT content, up to as high as 726 kJ. Keywords: Poly(propylene), Carbon nanotubes, Composites, Crystallization kinetics, DSC

Abstract licence: CC BY-NC-ND

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