Ablation behavior of elastomeric insulator based on nitrile rubber containing silica or silica-clay aerogels
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ORIGINAL RESEARCH
Ablation behavior of elastomeric insulator based on nitrile rubber containing silica or silica‑clay aerogels Morteza Fini Bidgoli1 · Fatemeh Arabgol2 · Mehrdad Kokabi1 Received: 21 February 2020 / Accepted: 3 August 2020 © Iran Polymer and Petrochemical Institute 2020
Abstract 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 (I80) 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. Keywords Aerogel · Silica-clay · Nanocomposite · Ablative insulator · Nitrile rubber
Introduction A high thermal protection problem has recently received much attention in the aerospace industries [1]. Combustion of solid rocket motor propellant produces turbulent media containing gases with a velocity of more than 1000 m/s at temperature and pressure more than 3000 °C and 10 MPa, respectively, which may destroy any metallic alloy [2]. Elastomeric nanocomposite heat insulators are more attractive than their similar non-elastomeric counterparts, due to their excellent thermal stresses and higher deformation bearing * Fatemeh Arabgol [email protected] * Mehrdad Kokabi [email protected] 1
Polymer Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, P.O. Box: 14115‑114, Tehran, Islamic Republic of Iran
Department of Chemical and Materials Engineering, Buein Zahra Technical University, Buein Zahra, P.O. Box: 3451745346, Qazvin, Iran
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[3]. Recent studies have endeavored to improve mechanical, thermal, and ablation properties of the elastomeric composites by using fibers [4], micro- and nanomaterials such as organoclay [2] and nanosilica [5]. Numerous ablative composites based on acrylonitrile butadiene rubber (NBR) [2, 6], ethylene propyle
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