The recycling of polyolefins for multiple life cycles is becoming a legislative requirement in the South African plastics industry. This study shows that this cannot be a blanket requirement for all polyolefins. While HDPE displays good resistance to weathering, the decrease in molecular weight limits the maximum number of life cycles before which the resultant product has lost all integrity. Impact polypropylenes fare much worse during weathering and more than 50% of impact properties are lost within the first 12 months of exposure. The blending of virgin material into degraded material can recover some properties of HDPE but not in the case of impact polypropylenes. The same legislation can therefore not be applied to all plastics and specific targets should depend on polymer composition.

中文翻译：

---

聚烯烃的多个生命周期的回收

聚烯烃多个生命周期的回收正在成为南非塑料行业的立法要求。这项研究表明，这不可能成为对所有聚烯烃的一揽子要求。虽然 HDPE 显示出良好的耐候性，但分子量的降低限制了最大生命周期数，在此之前所得产品将失去所有完整性。抗冲聚丙烯在风化过程中的表现要差得多，在暴露的前 12 个月内会损失超过 50% 的抗冲击性能。将原始材料与降解材料共混可以恢复 HDPE 的某些性能，但不能恢复抗冲聚丙烯的性能。因此，相同的立法不能适用于所有塑料，具体目标应取决于聚合物成分。