稀土氧化物对聚丙烯等温结晶动力学的影响

本文用差示扫描量热法测定了3种稀土氧化物对聚丙烯等温结晶行为的影响。结果表明,Avrami方程指数n、成核机理、晶体生长方式以及结晶晶型基本上不受稀土氧化物的影响。少量稀土氧化物可使结晶晶格垂直于分子链方向单位面积的界面自由能降低,结晶速率加大,其中Y_2O_3的效果最为显著,La_2O_3效果最低,混合稀土的作用效果与Y_2O_3相似。填加1wt%的Y_2O_3可使聚丙烯的结晶速度常数增大一个数量级。

EFFECT OF RARE EARTH OXIDES ON THE CRYSTALLIZATION KINETICS OF ISOTACTIC POLYPROPYLENE

The effect of three rare earth oxides, La_2O_3, Y_2O_3, and a mixture of rare earth oxides on the crystallization behavior of isotactic polypropylene (iPP) has been studied via differential scanning calorimetry (DSC). Avrami exponents n, the mechanism of nucleation, spherulite growth style and the crystal form of iPP have not been influenced badly by the rare earth oxides during the isothermal crystallization. However, a little of rare earth oxides will increase the crystallization rate and decrease the fold surface free energy, Oe, remarkable. This effect for Y_2O_3 most obvious and lowest for La_2O_3. The effect of the mixture of rare earth oxides is similar to the effect of Y_2O_3. By adding 1 wt% Y_2O_3 into iPP, the overall rate constant k in Avrami equation increases in one order.