Abstract:

Based on the polypropylene (PP) homopolymer and its copolymers with different ethylene contents, the effects of the contents of sorbitol nucleating agents and ethylene units on the crystallization kinetics, crystalline structure, crystalline morphology, transparency and mechanical property were systematically investigated. The self-organization behavior of the nucleating agent upon cooling was also analyzed through rheological behavior. The results show that, the crystallization, transparency and mechanical property of PP were dependent on the contents of nucleating agents and ethylene units. When the nucleating agent content increased to 0.1% (mass), the crystallization rates of PP and its copolymers were significantly accelerated, and their crystallinities were enhanced, resulting in the improvement of the rigidity of PP and its copolymers. However, the increase in ethylene unit content slows down the crystallization rate of PP, reduces the crystallinity and the rigidity of the material. The incorporations of ethylene units and nucleating agents facilitated the formation of γ crystals of PP. The relative fraction of γ crystals increased with increasing the contents of ethylene units and nucleating agents. As the contents of ethylene units and nucleating agents increased, the transparency of PP was also improved.

Key words: polypropylene, ethylene content, nucleating agent, crystallization, transparency

摘要：

基于聚丙烯(PP)均聚物和不同乙烯含量的PP共聚物，系统地研究了山梨醇类成核剂含量和乙烯单元含量对PP的结晶动力学、结晶结构、结晶形貌、透明性和力学性能的影响，并通过流变行为分析了成核剂在降温过程中的自组装行为。结果表明，PP的结晶、透明性和力学性能依赖于成核剂含量和乙烯单元含量。当成核剂含量增加到0.1% (质量分数)时，显著加快PP均聚物和共聚物的结晶速率，提高结晶度，提高材料的刚性。然而，乙烯单元含量的增加使PP的结晶速率减慢，降低结晶度，降低材料的刚性。乙烯单元和成核剂的加入都促进PP γ晶的形成，而且γ晶的相对含量随乙烯单元和成核剂含量的增加而增加。增加乙烯单元和成核剂含量也提高PP的透明性。

关键词: 聚丙烯, 乙烯含量, 成核剂, 结晶, 透明性