Silicone rubber is widely used in power grids, electronics and aerospace, because of its hydrophobicity, high flexibility, etc. However, it is susceptible to some environmental chemical factors, such as NO₂ and ozone, which can induce chain scission, the generation of defects and the ingress of water. In this work, we systematically studied the microstructure variations and water diffusion behavior of high-temperature vulcanized (HTV) silicone rubber after NO₂-induced oxidative damage. Microstructure evolution in silicone rubber was investigated by positron annihilation lifetime spectroscopy (PALS). The results show that the oxidation of NO₂ significantly degrades organic matrices, which induces the decrease of crosslinking degree and the formation of defects compared to virgin samples. The water transportation was evaluated by electrochemical impedance spectroscopy (EIS), which showed that the diffusion coefficient, under the NO₂ concentration of 28.75 mg L⁻¹, is 106 times that of virgin sample with a water uptake of 31%. Particularly, when the concentration reaches the critical value around 17.25 mg L⁻¹, the diffusion coefficient and water uptake increase sharply, and the calculated average porosity of samples also dramatically increases by 4 orders of magnitude. These indicate the formation of more nano- and micron holes, serving as a pointer for percolation of defects in silicone rubber bulk. The study of microstructure variations and water transportation can help us to understand the aging mechanism, design reasonable composite polymer materials and prevent the damage of chemical contact.

硅橡胶由于具有疏水性，高柔韧性等优点而被广泛用于电网，电子设备和航空航天。但是，它易受某些环境化学因素（例如NO ₂和臭氧）的影响，这些因素会引起断链，缺陷和进水。在这项工作中，我们系统地研究了高温硫化（HTV）硅橡胶在NO ₂引起的氧化损伤后的微观结构变化和水扩散行为。通过正电子an没寿命谱（PALS）研究了硅橡胶的微观结构演变。结果表明，NO ₂的氧化与原始样品相比，有机基质会显着降解，从而导致交联度降低和缺陷形成。通过电化学阻抗谱法（EIS）评价了水的输送，结果表明，在NO ₂浓度为28.75 mg L ^-1时，扩散系数是纯样品的扩散系数的106倍，吸水率为31％。特别是当浓度达到临界值约17.25 mg L ^-1时，扩散系数和吸水率急剧增加，并且计算出的样品平均孔隙率也显着增加了四个数量级。这些表明形成了更多的纳米和微米孔，作为渗漏硅橡胶块中缺陷的指标。对微观结构变化和水传输的研究可以帮助我们了解老化机理，设计合理的复合聚合物材料并防止化学接触的破坏。