RESEARCH ARTICLE Ablation behavior of organoclay‐NBR insulator: Modeling and experimental Fatemeh Arabgol | Mehrdad Kokabi | Ahmad Reza Bahramian Polymer Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, PO Box: 14115‐143 Tehran, Islamic Republic of Iran Correspondence Mehrdad Kokabi, Polymer Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, PO Box: 14115‐ 143 Tehran, Islamic Republic of Iran. Email: mehrir@modares.ac.ir Funding information Iran Nanotechnology Initiative Council (INIC); Tarbiat Modares University Summary Nitrile‐based nanocomposite heat insulators are very attractive materials compared with their similar nonelastomeric counterparts, due to their higher deformation bear- ing capacity in special applications. Modeling of these ablative nanocomposites enables us to determine the exact required thickness of the insulator and temperature distribution across it at predetermined thermal conditions. The complete form of the ablation equation is a transient nonlinear second‐order differential equation with var- iable temperature‐dependent thermo‐physical properties, which must be determined during thermal degradation. In this work, in addition to experimental investigation of ablative elastomeric nanocomposites based on NBR, the ablation process is modeled analytically with perturbation theory in the Lagrangian coordinate system because of surface recession and moving boundaries. Kirchhoff transformation was used to get rid of the temperature dependence of k in each zonal of virgin and char. The theoretical results were confirmed by experimental data obtained from the oxy- acetylene flame test. The results proposed a competitive nitrile‐based nanocomposite heat insulator with superior ablation properties: mass ablation rate 0.014 g s -1 , linear ablation rate 0.012 mm s -1 , and insulating index number 6800 s m -1 , under a standard test with a heat flux of 2500 kW m -2 for 15 seconds. KEYWORDS ablation, composite, modeling, nitrile, organoclay 1 | INTRODUCTION Thermal insulator for rocket motor chamber is one of the most impor- tant applications of the elastomeric ablative materials. Combustion of solid rocket motor propellant produces turbulent environment con- taining gases with a velocity, temperature, and pressure more than 1000 m/s, 3000°C, and 10 MPa, respectively, which destroys any metallic alloy. 1-3 Some charring ablators, which are made of thermosetting resin, such as phenolics, epoxies, polyesters, or ceramics, become rigid after curing and their surface cracks or blisters when exposed to high tem- perature and pressures; thus, these materials are essentially unwork- able as an insulator for such applications. 1,2 The flexible polymeric ablatives represent the widest family of sacrificial thermal protection system due to some intrinsic advantages such as tunable density, lower cost, and higher heat shock resistance, good processing, and mechanical properties and good flexibility, which can enable ablative materials to endure a variety of stresses due to operation and temperature changes. 3-6 Recent advances in nanocom- posite materials have been especially realized in their heat resistance and ablative performance due to their improved thermo‐physical and mechanical properties, which are important to enhance the insulation performance especially for rocket motor chamber in aerospace appli- cations. 5,7-10 Natali and his coworkers 3 summarized 50 years of research efforts on polymeric ablatives, starting from the state‐of‐the‐art solu- tions currently used as TPS, up to covering the most recent efforts for nanostructuring their formulations. All their main topics related to the science and technology of ablative materials with current and poten- tial applications in the aerospace industry. Among the common Received: 9 December 2016 Revised: 28 April 2018 Accepted: 7 May 2018 DOI: 10.1002/fam.2641 Fire and Materials. 2018;1–14. Copyright © 2018 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/fam 1