Upcycling of waste plastic film is increasingly important at the background of energy shortage and environmental crisis. However, direct reuse of the waste plastics as reworked material inevitably downgrades the mechanical properties. Herein, a stepwise crystallization method was used to enable the recycling of waste isotactic polypropylene (iPP) film value-added in iPP-based homocomposites. In detail, the effect of β-nucleating agent (β-NA) and iPP on crystallization behaviors of polypropylene random copolymer (PPR) was investigated at first. The stepwise crystallization procedure was further introduced to promote the β-crystallization of PPR/iPP/β-NA composites in which the crystal structures, polymorph compositions and phase morphologies were systematically researched. At last, impact behaviors of PPR/iPP/β-NA composites were characterized and a penitential toughening mechanism was proposed. It was found that the stepwise crystallization boosted β-crystallization and growth of rubbery phase during the isothermal procedure, resulting in an increase of relative β-crystal content and low temperature impact toughness from 0 % and 2.02 kJ/m2 of neat PPR to 33.4 % and 3.06 kJ/m2 of PPR/iPP/β-NA composites. This work provides a simple, implementable, and effective method for the recycling of waste iPP films and the low-temperature toughening of PPR.

中文翻译：

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逐步结晶法结合等规聚丙烯基塑料废膜制备高性能聚丙烯无规共聚物


在能源紧缺、环境危机的背景下，废旧塑料薄膜的升级回收显得愈加重要。然而，直接将废塑料作为再加工材料再利用不可避免地会降低机械性能。在此，采用逐步结晶方法，使废全同立构聚丙烯（iPP）薄膜的回收利用在iPP基均质复合材料中增值。具体而言，首先研究了β-成核剂（β-NA）和iPP对聚丙烯无规共聚物（PPR）结晶行为的影响。进一步引入逐步结晶过程来促进PPR/iPP/β-NA复合材料的β结晶，并对复合材料的晶体结构、多晶型组成和相形貌进行了系统研究。最后，对PPR/iPP/β-NA复合材料的冲击行为进行了表征，并提出了一种惩罚性增韧机制。结果发现，在等温过程中，逐步结晶促进了β-结晶和橡胶相的生长，导致相对β-晶含量和低温冲击韧性从纯PPR的0%和2.02 kJ/m2增加到33.4%以及 3.06 kJ/m2 的 PPR/iPP/β-NA 复合材料。该工作为废弃iPP薄膜的回收利用和PPR的低温增韧提供了一种简单、可实施、有效的方法。