Influence of the combination of nucleating agent and plasticizer on the non-isothermal crystallization kinetics and activation energies of poly(lactic acid)

The influence of the combination of the nucleating agent (talc, N, N '-ethylene bis-stearamide (EBS) and a commercial nucleating agent NT-20) and the plasticizer (poly(ethylene glycol), PEG) on the melting and crystallization behaviors of poly(lactic acid) (PLA) was investigated by means of differential scanning calorimetry (DSC). The Jeziorny's, Ozawa's and Mo's models were used to describe the non-isothermal cold and melt crystallization kinetics of the modified PLA samples. The non-isothermal cold and melt crystallization activation energies were evaluated by Kissinger's method and Friedman's method, respectively. The results show that the non-isothermal cold and melt crystallization kinetics of the samples are successfully analyzed by Jeziorny's and Mo's models, whereas Ozawa's model is only suitable for the non-isothermal melt crystallization kinetics of PLA/talc sample. It is shown that the combination of one nucleating agent and PEG results in the synergistic effect on the cold and melting crystallization rates of PLA. Moreover, the combination of dual nucleating agents and PEG improves the cold crystallization rate but hinders the melt crystallization rate. It is indicated that dual nucleating agents act as physical hindrance to the molecular chain movement of PLA which results in the increases in the cold and melt crystallization activation energies.