Nonisothermal Crystallization Behavior and Crystals Morphology of Poly(trimethylene terephthalate)/Nano-Calcium Carbonate Composites

摘要

Nonisothermal crystallization behavior and crystal morphology of poly(trimethylene terephthalate)(PTT)composites filled with modified nano-calcium carbonate(CaCO3)had been investigated by using differential scanning calorimetry and polarized optical microscopy.The modified Avrami equation and Ozawa theory were used to investigate the nonisothermal crystallization,respectively.The particles of nano-CaCO3,acting as a nucleation agent in composites,accelerated the crystallization rate by decreasing the half-time of crystallization or increasing the parameters of Z_c and K(T).Moreover,the nano-composite with 2 wt% nano-CaCO3 exhibited the highest crystallization rate.The Avrami and the Ozawa exponents,n and m of the nano-composites,were higher than those of neat PTT,suggesting more complicated interaction between molecular chains and the nanoparticles that cause the changes of the nucleation mode and the crystal growth dimension.The effective activation energy calculated from the Friedman formula was reduced as nano-CaCO3 content increased,suggesting that the nano-CaCO3 made the molecular chains of PTT easier to crystallize during the nonisothermal crystallization process.The optical micrographs showed that much smaller or less perfect crystals were formed in composites because of the presence of the nano-CaCO3 particles.