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Abstract：
Free radicals play a negative role during the thermal degradation of silicone rubber (SR). Quenching free radicals is proposed to be an efficient way to improve the thermal-oxidative stability of SR. In this work, a novel zirconium-containing polyhedral oligometallasilsesquioxane (Zr-POSS) with free-radical quenching capability was synthesized and characterized. The incorporation of Zr-POSS effectively improved the thermal-oxidative stability of SR. The T₅ (temperature at 5% weight loss) of SR/Zr-POSS significantly increased by 31.7 °C when compared to the unmodified SR. Notably, after aging 12 h at 280 °C, SR/Zr-POSS was still retaining about 65%, 60%, 75%, and 100% of the tensile strength, tear strength, elongation at break, and hardness before aging, respectively, while the mechanical properties of the unmodified SR were significantly decreased. The possible mechanism of Zr-POSS for improving the thermal-oxidative stability of SR was intensively studied and it was revealed that the POSS structure could act as a limiting point to suppress the random scission reaction of backbone. Furthermore, Zr could quench the free radicals by its empty orbital and transformation of valence states. Therefore, it effectively suppressed the thermal-oxidative degradation and crosslinking reaction of the side chains.
摘要：
自由基在硅橡胶（SR）的热降解过程中起着负面影响。自由基猝灭被认为是改善SR的热氧化稳定性的有效方法。在这项工作中,合成并表征了具有自由基猝灭能力的新型含锆多面体低聚硅倍半硅氧烷（Zr-POSS）。Zr-POSS的掺入有效地改善了SR的热氧化稳定性。与未改性的SR相比，SR/Zr-POSS的Tt（重量损失5％时的温度）显着增加了31.7°C。值得注意的是,在280°C下老化12小时后，SR/Zr-POSS仍保留约65%，60%,75%,和100%的抗拉强度，撕裂强度,断裂伸长率,和老化前的硬度，分别,而未改性SR的力学性能显著下降。深入研究了Zr-POSS提高SR热氧化稳定性的可能机理，发现POSS结构可以作为抑制骨架随机断裂反应的极限点。此外，Zr可以通过其空轨道和价态转变来淬灭自由基。因此,它有效地抑制了侧链的热氧化降解和交联反应。
