In the present study, two-step foaming procedure with a designed in-situ foaming observation apparatus was used to study the foaming dynamics of styrene-methyl methacrylate (St-MMA) copolymer/nanosilica composites. For this purpose, the St-MMA copolymer was synthesized using suspension copolymerization and its nanocomposites were prepared using solution method. The foaming dynamics was studied through temperature-induced (two-step batch foaming) method. Furthermore, the effects of content, size and surface chemistry of silica nanoparticles on the impregnation process, the foaming dynamics and the final morphology of prepared foams were investigated. The impregnation data showed that the presence of silica nanoparticles in matrix prolonged the impregnation and decreased diffusion coefficient. This effect would be clearer where nanoparticle contents are high and the temperature is quite above Tg. The foaming dynamics results illustrated that the nucleation and foaming rate were enhanced with the nanoparticle addition and its size reduction. At the St-MMA copolymer foaming system, the silica nanoparticles with hydrophilic surface chemistry are more efficient in comparison to hydrophobic nanoparticles where all foaming dynamics and the final microstructure parameters were improved.

中文翻译：

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二氧化硅纳米粒子对苯乙烯-甲基丙烯酸甲酯共​​聚物/正戊烷泡沫的浸渍过程、发泡动力学和泡孔微观结构的影响

在本研究中，使用设计的原位发泡观察装置的两步发泡程序来研究苯乙烯-甲基丙烯酸甲酯 (St-MMA) 共聚物/纳米二氧化硅复合材料的发泡动力学。为此，使用悬浮共聚法合成了 St-MMA 共聚物，并使用溶液法制备了其纳米复合材料。通过温度诱导（两步间歇发泡）方法研究发泡动力学。此外，研究了二氧化硅纳米粒子的含量、尺寸和表面化学对浸渍过程、发泡动力学和制备的泡沫最终形态的影响。浸渍数据表明，基体中二氧化硅纳米粒子的存在延长了浸渍时间并降低了扩散系数。在纳米颗粒含量高且温度远高于 Tg 的情况下，这种效果会更加明显。发泡动力学结果表明，随着纳米颗粒的加入和纳米颗粒的减小，成核和发泡速率得到提高。在 St-MMA 共聚物发泡系统中，与所有发泡动力学和最终微观结构参数都得到改善的疏水性纳米颗粒相比，具有亲水表面化学性质的二氧化硅纳米颗粒更有效。