Polypropylene‐grafted nanosilica (PP‐g‐SiO₂) was prepared by us as a new modified nanosilica with long polymer chains and high grafting density. It was found that the addition of PP‐g‐SiO₂ resulted in remarkable strain‐hardening behavior of PP. Herein, the foaming behavior of isotactic polypropylene (iPP)/PP‐g‐SiO₂ nanocomposites was investigated by using supercritical carbon dioxide (scCO₂) as a blowing agent. The results demonstrated that the incorporation of PP‐g‐SiO₂ could obviously enhance the foamability of iPP. In particular, the uniform cell distribution and smaller cell size could be obtained by 1 wt% particle loading, and 5 wt% particle content showed a wider foaming temperature range and higher cell density. The noticeable enhancement in the foamability of iPP was attributed to the reinforced melt strength, high melt elasticity and the increased heterogeneous nucleation caused by well dispersed and long polypropylene chains grafted SiO₂. These findings provide new insights to improve the foaming ability of iPP with incorporation of modified nanoparticles.

中文翻译：

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等规聚丙烯/聚丙烯接枝纳米二氧化硅纳米复合材料在超临界二氧化碳中的发泡性增强

由我们制备的聚丙烯接枝纳米二氧化硅（PP-g-SiO ₂）是一种新型的改性纳米二氧化硅，具有长聚合物链和高接枝密度。结果发现，添加PP-g-SiO _2会导致PP显着的应变硬化行为。本文中，以超临界二氧化碳（scCO ₂）为发泡剂，研究了等规聚丙烯（iPP）/ PP-g-SiO ₂纳米复合材料的发泡行为。结果表明，PP-g-SiO ₂的引入可以明显提高iPP的发泡性。特别地，通过1重量％的颗粒负载可以获得均匀的孔分布和较小的孔尺寸，并且5重量％的颗粒含量显示较宽的发泡温度范围和较高的孔密度。iPP发泡性的显着提高归因于良好分散的聚丙烯链和接枝长的SiO ₂引起的增强的熔体强度，高熔体弹性和增加的不均匀成核。这些发现提供了新的见解，以通过结合改性的纳米颗粒来改善iPP的发泡能力。