Abstract Microcellular poly(vinyl alcohol) (PVA) foams were prepared by combing the thermoplastic processing technology and solid-state supercritical CO2 foaming technology. The compound polyol plasticizers that may partially destroy intra- and inter-molecular hydrogen bonding within PVA and improve the flowability during processing were developed to pave the way for PVA thermoplastic processing with lower processing temperature and wider processing window. In order to ease the collapse of bubbles and improve the foaming performances, nano silica was introduced into the system. The influences of processing parameters (foaming temperature and saturation pressure) and nano silica content on the foaming behavior and cell structure were systematically studied. The resultant PVA/SiO2 nanocomposite foams exhibited a cellular structure with smaller cell size, larger cell density and relative density compared to PVA foam. It was also found that cell density increased with decreasing foaming temperature or increasing saturation pressure. Further investigation suggested that improvement of stiffness as well as the decrease of crystallinity were thought as the main reasons to explain the interesting effect of SiO2 addition on the foaming behavior of PVA.

中文翻译：

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纳米二氧化硅在热塑性聚乙烯醇超临界 CO 2 发泡中的作用及其对泡孔结构和力学性能的影响

摘要 结合热塑性加工技术和固态超临界CO2发泡技术制备了微孔聚乙烯醇(PVA)泡沫。开发了可部分破坏PVA分子内和分子间氢键并改善加工过程中流动性的复合多元醇增塑剂，为PVA热塑性塑料加工铺平了道路，具有更低的加工温度和更宽的加工窗口。为了缓解气泡的坍塌和提高发泡性能，在体系中引入了纳米二氧化硅。系统研究了工艺参数（发泡温度和饱和压力）和纳米二氧化硅含量对发泡行为和泡孔结构的影响。与 PVA 泡沫相比，所得的 PVA/SiO2 纳米复合泡沫表现出具有更小的孔尺寸、更大的孔密度和相对密度的多孔结构。还发现泡孔密度随着发泡温度的降低或饱和压力的增加而增加。进一步的研究表明，刚度的提高和结晶度的降低被认为是解释 SiO2 添加对 PVA 发泡行为有趣影响的主要原因。