Cross-linked polyethylenes (PEs) are widely employed, but the permanent links between the chains impede recycling. We show that via imine formation with diamines keto-functionalized polyethylenes from both free-radical (keto-low-density PE, keto-LDPE) and catalytic (keto-high-density PE, keto-HDPE) nonalternating ethylene-CO copolymerization can be cross-linked efficiently in the melt, resulting in gel fractions of the formed cross-linked PEs of up to 85% and improved tensile properties. The imine-based cross-links in the material can be hydrolyzed at 140 °C to recycle up to 97% of the initial thermoplastic keto-polyethylene. Low keto contents of ≤1.5 mol % are found ideal to retain PE-like thermal properties, achieve sufficient cross-link density, and maintain circular recyclability.

中文翻译：

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由链内酮实现的圆形交联聚乙烯


交联聚乙烯 （PE） 被广泛使用，但链条之间的永久连接阻碍了回收利用。我们表明，通过与二胺形成亚胺，来自自由基（酮-低密度 PE、酮-LDPE）和催化（酮-高密度 PE、酮-HDPE）非交替乙烯-CO 共聚物的酮官能化聚乙烯可以在熔体中有效交联，从而产生高达 85% 的形成交联 PE 的凝胶级分并改善拉伸性能。材料中的亚胺基交联可以在 140 °C 下水解，以回收高达 97% 的初始热塑性酮聚乙烯。≤1.5 mol % 的低酮含量被发现非常适合保持类似 PE 的热性能，实现足够的交联密度，并保持循环可回收性。