Study of Non-isothermal Crystallization Kinetics of Single-walled Carbon Nanotubes Filled Polypropylene Using Avrami and Mo Models

The kinetics of non-isothermal crystallizations of polypropylene (PP) and PP containing 0.5 wt% single-walled carbon nanotube (PP/SWNT) were compared by using differential scanning calorimetry technique. The non-isothermal melt crystallization data were analyzed according to Avrami and Mo models. The values of halflife and corrected composite rate constant of Avrami equation as well as the rate parameter of Mo equation indicated that the crystallization rate increased with the increasing of PP and PP/SWNT cooling rates. However, the crystallization rate of the nanocomposite was found to be higher than that of PP at a certain cooling rate. Nucleation efficiency (NE) defined by Fillon was obtained for PP/SWNT. It was found that NE varied from 16.4% to 19.4% in the range of cooling rate studied. This implied that SWNT could play as a nucleating agent for the crystallization of PP. In addition, the effective energy barrier (ΔE) for the non-isothermal melt crystallization process was calculated for the two materials by using the Kissinger method. The ΔE values were determined to be 226 and 262 kJmol-1 for PP and PP/SWNT, respectively. Based on the theory proposed by Lauritzen and Hoffman, the end surface free energy (σe) for the two materials was calculated. The results showed that the value of σe for the nanocomposite was lower than that of PP itself, in agreement with the fact that the rate of crystallization is higher in the nanocomposite compared to the pristine polymer.