蒙脱土/聚丙烯成核机理的α→β转变

蒙脱土(MMT)填充等规聚丙烯(i PP)仅形成α-晶。该文利用MMT的Ca2+与庚二酸(PA)反应形成庚二酸钙(Ca PA)制备了表面负载β-成核剂的MMT(β-MMT),FTIR和TGA证实了β-MMT表面Ca PA的形成。采用DSC和XRD研究了β-MMT填充i PP纳米复合材料的β-成核作用和β-晶含量,观察到随着MMT/PA质量比减小(即PA用量增加),i PP复合材料的结晶峰温提高,α-晶熔融峰强逐渐减弱,β-晶熔融峰强逐渐增强,最后仅出现β-晶熔融单峰,表明β-成核作用增强。XRD结果表明随着MMT/PA质量比减小,β-晶含量逐步提高,当MMT/PA质量比为100制备的β-MMT填充i PP纳米复合材料全部形成β-晶。以上结果表明,MMT粒子表面负载β-成核剂可实现MMT填充i PP复合材料结晶从α-晶转变为β-晶。

Transformation from α to β of Nucleation Mechanism of Montmorillinite Filled Isotactic Polypropylene Composites

Montmorillontie (MMT) filled isotactic polypropylene (iPP) forms α-crystal. In this paper, β-MMT with β-nucleating surface supported by calcium pimelate (CaPA) was prepared through chemical reaction between Ca²⁺ and pimelic acid (PA). The results of FTIR spectroscopy and TGA analysis of β-MMT confirmed the formation of CaPA on the surface of MMT. The crystallization temperature, β-nucleating ability and the β-crystal content of β-MMT filled iPP composites were investigated by DSC and XRD analyses. It was observed that the crystallization temperature and intensity of β crystal melting peak increased with decreasing MMT/PA mass ratio, indicating the enhanced β-nucleating ability. The XRD results showed that the β-crystal contents of β-MMT filled iPP composites increased with decreasing MMT/PA mass ratio. In addition, MMT filled iPP composites with β-crystal of 99% could be obtained by β-MMT prepared with MMT/PA mass ratio of 100. These results indicated that the β-nucleating agent supported on the surface of MMT particles could change from α- to β-nucleation in the MMT filled iPP composites.