聚丙烯/累托石纳米复合材料的非等温结晶动力学研究

在双螺杆挤出机上熔融共混制备了聚丙烯 (PP) 有机累托石 (OREC)纳米复合材料 ,采用广角X 射线衍射 (WAXD)定性地分析了PP OREC纳米复合材料及纯PP的结晶形态 ,由半峰宽定性地判断了对应晶面法向的晶粒的大小 .结果表明有机累托石没有改变聚丙烯的结晶晶型 (纳米复合材料主要还是α晶型 ) ,但是细化了晶粒的尺寸 .采用差示扫描量热法 (DSC)定量地研究了复合材料的非等温熔融结晶动力学 ,对所得数据分别用Jeziorny法的Mo法进行了处理 ,表明非等温结晶动力学参数Zc 及Avrami指数n随冷却速率的增加而增加 ,复合材料的Avrami指数n大于纯PP的n ;对相同配比的纳米复合材料 ,随着结晶度的增加 ,单位结晶时间里达到一定结晶度所需要的降温速率F(T)增大 ,对同一个设定的结晶度 ,纳米复合材料的F(T)比纯PP的小 ,说明需要的降温速率减小 .所有这些均说明有机累托石可作为聚丙烯的结晶成核剂 .

NON-ISOTHERMAL CRYSTALLIZATION KINETICS OF POLYPROPYLENE/ORGANIC-RECTORITE NANOCOMPOSITES

The polypropylene (PP)/organic rectorite(OREC) nanocomposites were prepared by extruding the mixtures of OREC and PP using a twin-screw extruder. The crystallization behavior of PP and PP/OREC nanocomposites was studied by wide angle X-ray diffraction analysis (WAXD) performed at angle range of 10～25°and differential scanning calorimetry (DSC) conducted at constant cooling rate of 2.5、K/min,5、K/min,10、K/min and 15、K/min, respectively. The results of WAXD analysis show that the introduction of OREC does not change the crystal form of PP in the compocites. Non-isothermal crystallization kinetics of PP and PP/OREC nanocomposites was investigated by means of DSC, and the data are successfully analyzed by the Jeziorny and the Mo Zhishen methods. The non-isothermal crystallization kinetics parameter (Z c) and Avrami exponent(n) for PP and PP/OREC nanocomposites were reduced with cooling rate increasing. However, for PP/OREC nanocomposites, they are higher than those of PP at the same cooling rate. The characteristic cooling rate, F(T), increases with the degree of crystallinity for both PP and PP /OREC nanocomposites, but the values of F(T) of PP/OREC nanocomposites were lower than those of PP at the same degree of crystallinity. All the above analyse indicate that particles of OREC have heterogeneous nucleation effects on PP matrix.