Evaluation of lightweight and flexible insulating aerogel blankets based on Resorcinol-Formaldehyde-APTES-MTES for space applications
Résumé
In space conditions, insulation is provided by Multi-Layer Insulation (MLI) which is the most efficient technical solution in vacuum [1]. However, when the external pressure increases above zero (for cargo modules or manned or unmanned compartments in ascent/(re-)entry vehicles or on the surface of planets presenting an atmosphere) performance decreases rapidly and alternative materials are needed. Silica aerogels are light and the most thermally insulating solid materials but they are mechanically fragile. To strengthen silica aerogels without deteriorating their very low thermal conductivity, methods such as organic-inorganic hybridization are studied [2-3]. In this study, we have synthesized and characterized new hybrid organic-inorganic aerogel blankets for space applications. Aerogel blankets were produced using a one-pot synthesis method with a PET unwoven fibrous network core, resorcinol (R), formaldehyde (F) and a silica precursor (APTES with or without MTES or MTMS as silica co-precursors). We modified the composition of the sol in order to correlate the chemical parameters to the physico-chemical characteristics of the resulting material such as chemistry, texture (density and porosity), hydrophilicity, thermal conductivity and mechanical properties. Using the RF-APTES-MTES chemical system we were able to obtain a flexible hybrid blanket with both low apparent density (0.04 g.cm-3) and relatively low effective thermal conductivity (0.027 W.m-1K-1 in room conditions). A proof of concept is done by evaluating panels constituted of encapsulated aerogel blanket in vacuum and low pressure atmosphere. The blankets show a combination of key characteristics representing the right mix for thermal insulations in space applications operating in non-vacuum environments. This research was funded by the European FP7 program (AerSUS project). [1] J. Fesmire et al., International Cryogenics Engineering Conference 19, Narosa Publishing house, p 843-846 (2002). [2] H. Maleki et al., J. Non-Cryst. Solids, 385, 55-74 (2014). [3] S. Berthon-Fabry et al., Eur. Polym. J. 78, 25–37(2016)