原位聚合聚乙烯/蒙脱土纳米复合材料的结晶行为

用DSC研究了HDPE与MMT负载的催化剂熔融共混和原位聚合得到的两种纳米复合材料的熔融、 结晶行为和等温结晶动力学.  结果表明, HDPE与熔融共混样品的结晶度、 平衡熔点、 球晶生长速率和结晶能力大体相同; 原位聚合得到的HDPE/MMT纳米复合材料的结晶度和平衡熔点高于纯HDPE; 在相同过冷度条件下熔融结晶速率和结晶能力低于纯HDPE, 而在相同结晶温度Tc下, 熔融结晶速率和结晶能力则高于纯HDPE.  纯HDPE的晶体生长侧向单位面积表面自由能最小, 其次是熔融共混样品, 原位聚合样品最大, 且随ＭＭＴ含量的增加逐渐升高.

Crystallization Behavior of Polyethylene/Montmorillonite(MMT) Nanocomposites by in Situ Polymerization

The crystallization kinetics isothermally,  the melting and crystallization behavior of pure HDPE,  HDPE/MMT blends and HDPE/MMT nanocomposites prepared by in situ polymerization were investigated by DSC. The crystallinity,  linear growth rate of spherulites,  equibrium melting temperature and crystallization ability of HDPE are similar to that of its blends with MMT. However, the crystallinity and equibrium melting temperature of PE/MMT nanocomposites by in situ polymerization are higher than that of HDPE.  The linear growth rate of spherulites and crystallization ability of the crystals formed at the same undercooling degree are lower for HDPE/MMT nanocomposites in comparison with HDPE.  On the other hand,  they are much higher when the crystals crystallized from melt at the same temperature, tc,  for HDPE/MMT nanocomposite.  The lateral surface free energy,  σ,  of the developing crystals is the smallest for HDPE,  secondly it is for the HDPE/MMT blends,  the HDPE/MMT nanocomposites exhibit the largest σ and it increased gradually with increasing the content of MMT in these composites.