聚丙烯共混体系结晶行为及发泡性能研究

摘要

Foaming of polypropylene homo polymer(PP-H),polypropylene block copolymer(PP-B) and PP-H/PP-B blend system by using supercritical CO2 as foaming agent at a typical condition were studied. The crystallization behavior,crystal structure and morphology were characterized using differential scanning calorimetry and polarized optical microscope. The melt strength was characterized indirectly using meltflow rate tester. The morphology of the foams was observed by scanning electron microscope . The foaming behaviors of them were compared. Results show that PP-B is not only used as crystallization nucleating agent to make the spherocrystalfine and increase the density of crystallization,but also used as physical cross-link point to enhance the melt strength in the PP-H/PP-B blend system at the rate of 70∶30. The changes of the two aspects improve the foaming property of the blend system effectively,resulting in much smaller cell size,higher cell density and unbroken cells.%以均聚聚丙烯(PP-H)，嵌段共聚聚丙烯(PP-B)及其共混体系为研究对象，以超临界CO2为发泡剂，选择典型工艺条件进行发泡实验，采用差示扫描量热仪和偏光显微镜研究共混前后样品的结晶行为和球晶形貌，通过熔体流动速率测试仪间接表征其熔体强度，然后采用扫描电子显微镜观察发泡样品的泡孔形态，比较其发泡行为。研究结果表明：在共混比例为70∶30的PP-H/PP-B共混体系中，由于结晶温度较高，PP-B不仅可以作为结晶成核剂，细化球晶并提高结晶密度，而且还可以作为物理交联点，提高体系的熔体强度。这两方面的改变有效地改善了共混体系的发泡性能，使其泡孔尺寸显著减小，泡孔密度有所提高并且没有明显的泡孔塌陷。