Flame retardant rubber foams of ethylene vinyl acetate (EVA)/natural rubber (NR)/layered silicate blends filled with silicon dioxide (SiO₂) were prepared by using azodicarbonamide (ADC) as a blowing agent. Specifically, SiO₂ was added in EVA/NR blend nanocomposites to produce good flame retardant foams. The properties of EVA/NR blend nanocomposite foams with different SiO₂ loading (0, 20, 30, 40 parts per hundred rubber, phr) were investigated through transmission electron microscopy (TEM), scanning electron microscopy (SEM), rheological property test, mechanical property measurement, flammability tests, thermogravimetry analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry (Pyrolysis-GC-MS). Compared with the simple EVA/NR blend nanocomposite, the added SiO₂ increased the blend compatibility between EVA and NR phases and melt strength/viscosity of the EVA/NR blend nanocomposites, thus promoting cellular structure of the EVA/NR nanocomposite foams. Increasing SiO₂ loading resulted in higher cell density, smaller cell size, and lower volume of void. These improvements caused higher strength and elastomeric recovery. The LOI test results showed that flame retardancy of the EVA/NR blend nanocomposite foams increased at higher SiO₂ loading as a result of formation of insulation silicon dioxide-based char. TGA and pyrolysis-GC-MS analyses also validated the finding that the silicon dioxide-based char in the foamed samples containing higher SiO₂ loading was more effective on improving thermal stability, which was responsible for lower material combustibility and better flame retardancy. Based on our finding, it was concluded that a good flame retardant EVA/NR blend nanocomposite foam with the best improvement in strength and elastomeric recovery was achieved when combined with 40 phr SiO₂.

以偶氮二甲酰胺（ADC）为发泡剂，制备了填充有二氧化硅（SiO ₂）的乙烯醋酸乙烯酯（EVA）/天然橡胶（NR）/层状硅酸盐共混物的阻燃橡胶泡沫。具体而言，将 SiO ₂添加到 EVA/NR 共混纳米复合材料中以产生良好的阻燃泡沫。不同SiO ₂的EVA/NR共混纳米复合泡沫的性能通过透射电子显微镜 (TEM)、扫描电子显微镜 (SEM)、流变性能测试、机械性能测量、可燃性测试、热重分析 (TGA) 和热解-气相色谱-质谱（热解-GC-MS）。与简单的 EVA/NR 共混纳米复合材料相比，添加的 SiO ₂增加了 EVA 和 NR 相之间的共混相容性以及 EVA/NR 共混纳米复合材料的熔体强度/粘度，从而促进了 EVA/NR 纳米复合泡沫的多孔结构。增加SiO ₂加载导致更高的细胞密度、更小的细胞尺寸和更低的空隙体积。这些改进导致更高的强度和弹性恢复。LOI 测试结果表明，由于形成绝缘二氧化硅基炭，EVA/NR 共混纳米复合泡沫的阻燃性在较高的 SiO ₂负载下增加。TGA 和热解-GC-MS 分析还验证了以下发现：含有较高 SiO ₂的泡沫样品中的二氧化硅基炭负载对提高热稳定性更有效，这是降低材料可燃性和更好阻燃性的原因。根据我们的发现，得出的结论是，当与 40 phr SiO ₂组合时，可实现具有最佳强度和弹性回复率的良好阻燃 EVA/NR 共混纳米复合泡沫。