Ablation behavior of elastomeric insulator based on nitrile rubber containing silica or silica-clay aerogels

Nitrile-based nanocomposite heat insulators are very attractive materials, due to their higher deformation bearing in special applications such as high temperature and turbulent media, compared to their non-elastomeric counterparts. Ablation behavior of nitrile rubber-based insulators containing silica and silica-clay aerogels was investigated in comparison with those containing fumed silica. An oxyacetylene flame test under a standard condition with a heat flux of 2500 kW m(-2)for 15 s was used for observation of ablation behavior of the samples. The results showed that the incorporation of 15 phr (part per hundred parts of rubber) silica aerogel into the compound decreased the mass of insulator and its linear ablation rate by 15% and 29%, respectively. The incorporation of 5 wt% organoclay in silica aerogel successfully reduced the linear ablation rate to nearly 41%. The results indicated that the insulation index number (I-80) of the insulators increased about 29% and 20%, at this loading levels of silica and silica-clay aerogels, respectively. Therefore, silica aerogel played more effective role in reduction of the back-face temperature of insulators. Modeling of these ablative nanocomposites enables us to determine the exact thickness required for the insulator and the temperature distribution across it at pre-determined thermal conditions. The experimental results confirmed modeling results of the back-face temperature of the insulators.