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通过广角X射线衍射(WAXD)、示差扫描量热(DSC)和偏光显微镜(POM)研究了长链支化聚丙烯(LCBPP)和线性等规聚丙烯(PP)的结晶行为.WAXD和DSC的结果显示LCBPP样品有利于β结晶,出现了少量β晶.DSC和POM的结果显示在等温结晶过程中长链支化结构起到促进异相成核和细化晶粒的作用,LCBPP样品的结晶温度提高,结晶速度增大,球晶尺寸显著减小.采用间歇釜式超临界二氧化碳发泡法对LCBPP和线性PP样品进行发泡,由于LCBPP结晶温度高,结晶速率更快,有利于泡孔的固化定型,可以提高发泡温度,研究结果表明在相同的发泡压力下LCBPP样品发泡温度窗口较宽,为5 K左右,而线性PP样品的发泡温度窗口较窄,仅为2 K左右,同时在相同的发泡条件下LCBPP样品的发泡倍率较大.
The crystallization behavior of long chain branched polypropylene (LCBPP) and linear isotactic polypropylene (PP) was investigated by wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and polarized light microscopy (POM) The results showed that the LCBPP samples favored beta crystallization with a small amount of beta crystals.The results of DSC and POM showed that the long chain branched structure promoted the heterogeneous nucleation and grain refinement during isothermal crystallization and the crystallinity of LCBPP samples The temperature and the crystallization rate increased, and the spherulite size decreased significantly.Using the batch-type supercritical carbon dioxide foaming method to foam LCBPP and linear PP samples, the crystallization rate of LCBPP was higher and the crystallization rate was faster, The results show that at the same foaming pressure, the foaming temperature window of LCBPP sample is wide at about 5 K, while the linear PP sample has a narrow foaming temperature window of only 2 K While the foaming magnification of LCBPP samples is larger under the same foaming conditions.