幾十年來，研究人員一直在研究使用無機顆粒來提高高分子泡材的泡孔密度。傳統上，研究人員使用成核劑來增強和控制氣泡成核。 在本研究中，我們使用兩種未經和經表面處理的氣相二氧化矽顆粒AEROSIL® 200 (A200) 和 AEROSIL® R974 (R974)，作為TPU的 發泡成核劑，並使用超臨界 CO2 作為發泡劑。
結果顯示，氣相二氧化矽是一種良好的泡孔成核劑。 與純 TPU 泡材相比，添加 1 wt% 的氣相二氧化矽可使泡孔密度增加約兩個數量級，並且平均泡孔尺寸減小。 添加氣相二氧化矽不改變結晶溫度（Tc）； 熔化熱 (ΔHm) 僅略有下降。 另外，添加氣相二氧化矽作為成核劑也不會顯著改變黏度，這些特性對高分子加工非常有利。

For decades, researchers have investigated the use of inorganic particles to enhance the cell density of polymeric foams. Traditionally, researchers use a nucleating agent to enhance and control cell nucleation. In this study, two fumed silica particles were applied as nucleating agents in MDI/BD/PTMEG-based TPUs for foaming, and supercritical CO2 was used as the blowing agent. Two fumed silica particles, AEROSIL® 200 (A200) and AEROSIL® R974 (R974), without and with surface treatment, are mixed with four different TPUs grades with different hardness.
The results showed that fumed silicas are cell nucleating agents. The adding 1 wt% fumed silica increased the cell density by about two orders of magnitude, and the average cell size decreased compared to neat TPUs foam. Adding fumed silica did not change the crystallization temperature (Tc); the fusion heat (ΔHm) only slightly decreased. Adding fumed silica as a nucleation agent did not significantly alter viscosity, which is ideal for polymer processing.

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