Ablation behavior of organoclay‐NBR insulator: Modeling and experimental

Abstract

Summary Nitrile‐based nanocomposite heat insulators are very attractive materials compared with their similar nonelastomeric counterparts, due to their higher deformation bearing 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 variable 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 oxyacetylene 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.

Evaluation of elastomeric heat shielding materials as insulators for solid propellant rocket motors: A short review

“…Linear ablation rates as low as 0.012 mm/s have been reported for organoclay/NBR nanocomposite HSM. Modeling of these ablative nanocomposites has been performed to determine the exact required thickness of the insulator and the temperature distribution across it at specific thermal conditions [44]. Silicone-based EHSM are found in the state of the art of insulator formulations [9,11,45] specially for specific spacecraft applications, many times using costly additives such as the polyhedraloligosilsesquioxane (POSS) and carbon fibers.…”

“…The use of various reinforcements together opens wider possibilities for obtaining efficient EHSM. Arabpol et al [44] have used fumed silica, organoclay, and short carbon fibers in NBR, achieving ablation rates comparable to those obtained with EPDM or even lower. Carbon composites via a low-temperature carbonization of NBR elastomer compounds and highly filled with various carbon fillers and dispersed silicon carbide (SiC) were developed.…”

Ablation Response Behavior under Different Heat Flux Environments for Liquid Silicone Rubber Composites

“…Traditional rigid insulators are difficult to adapt to the large load deformation of the complex connecting structure and the maneuvering structure during the hypersonic flight due to their weak deformation ability. 9 In contrast, flexible ablators are a class of materials that can adapt to large deformations, have a large elongation at break and elasticity, and can adapt to longterm atmospheric flight environments. 10 They show unique advantages in complex deformation and dynamic structure, 11 which can effectively make up for the drawback of rigid insulators.…”

Enhancing Mechanical and Thermal Properties of NBR/Nano-Silica by Proper Loading of Organoclay

“…Recently, fumed silica has been widely used to enhance the mechanical and thermal properties of rubber [1]. The influence of adding 15 phr the fumed silica or silica aerogel or both of them in nitrile rubber have been investigated in nitrile rubber and has been investigated [2,3]. Moreover, an increase in the electrical insulating properties of NBR-silica (15-20 phr) nanocomposite based on NBR has been shown the proper electrical insulation properties at 15 phr [4].…”