Polypropylene (PP)-based composites have attracted numerous attention as a replacement of prevailing cross-linked polyethylene (XLPE) for high-voltage insulation due to their ease of processing, recyclability, and excellent electrical performance. However, the poor resistances against high-temperature creep and thermal aging are obstacles to practical applications of PP-based thermoplastic high-voltage insulation. To address these problems, in this Letter, we synthesized an impact polypropylene copolymer (IPC) containing multifold long-chain branched (LCB) structures in phases, especially the interfaces between the PP matrix and the rubber phase. The results indicated that the structural stability of LCBIPC was significantly enhanced under extreme conditions. In comparison to IPC (without LCB structures), 24.1% less creep strain and 75.2% less unrecoverable deformation are achieved in LCBIPC at 90 °C. In addition, the thermal aging experiments were performed at 135 °C for 48 and 88 days for IPC and LCBIPC, respectively. The results show that the resistance against thermal aging was also enhanced in LCBIPC, which showed a 133% longer thermal aging life compared to IPC. Further results revealed that the interfacial layer between the PP matrix and the rubber phase was constructed in LCBIPC. The two phases are tightly linked by chemical bonds in LCB structures, leading to enforced constraints of the rubber phase at the micro level and better resistance performance against creep and thermal aging at the macro level. Evidently, the reported eco-friendly LCBIPC thermoplastic insulation shows great potential for applications in high-voltage cable insulation.

中文翻译：

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通过长链支化界面约束大幅提高环保聚丙烯高压绝缘的抗蠕变性和热老化稳定性


聚丙烯（PP）基复合材料由于其易于加工、可回收性和优异的电气性能，作为高压绝缘领域流行的交联聚乙烯（XLPE）的替代品而受到广泛关注。然而，聚丙烯基热塑性高压绝缘材料的耐高温蠕变和热老化性能较差，阻碍了其实际应用。为了解决这些问题，在这封信中，我们合成了一种抗冲聚丙烯共聚物（IPC），该共聚物在各相中含有多重长链支化（LCB）结构，特别是在聚丙烯基体和橡胶相之间的界面处。结果表明，LCBIPC的结构稳定性在极端条件下显着增强。与 IPC（无 LCB 结构）相比，LCBIPC 在 90 °C 时的蠕变应变减少了 24.1%，不可恢复变形减少了 75.2%。此外，IPC和LCBIPC分别在135℃下进行了48天和88天的热老化实验。结果表明，LCBIPC 的抗热老化性能也得到了增强，与 IPC 相比，其热老化寿命延长了 133%。进一步的结果表明，PP 基体和橡胶相之间的界面层是在 LCBIPC 中构建的。 LCB结构中的两相通过化学键紧密连接，从而在微观层面上对橡胶相进行了强制约束，并在宏观层面上实现了更好的抗蠕变和热老化性能。显然，所报道的环保型LCBIPC热塑性绝缘材料在高压电缆绝缘材料方面显示出巨大的应用潜力。