Flexible Silica Aerogels - Material Development and Characterization for the Insulation of Aircraft Cabins

Abstract

Reasoned with their extraordinary properties in terms of density and thermal conductivity enabling a wide range of technological applications, silica aerogels have received increasing interest in research. Unfortunately, conventional silica aerogels are often brittle and unpleasant to handle. Due to the adaptable sol-gel-processing, a remarkable variety of customisable properties enabled the development of flexible aerogels with improved handling. Hayase et al. developed an aerogel based on methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS), which not only exhibits flexibility, but also outstanding hydrophobicity. Lightweight and hydrophobic materials are crucial in aerospace applications, since water vapour emitted by passengers condenses within state of the art, rather hydrophilic insulation materials like fiberglass pads. As a result accumulation of water proceeds, leading to icing and a significant increase in weight. Often, this ice does not melt and drain during turn around, as these times are meant to be decreased in terms of efficiency increase by the carriers. This leads to a further weight increase and unnecessary fuel consumption on each flight. In order to solve this problem, functionalised silica aerogels represent a potentially suitable replacement of fiberglass pads. However, the hydrophobization of insulation materials like aerogels via integration of methyl-substituted silica precursors (like MTMS and DMDMS) results in increased flammability and density. For that matter, various approaches to decrease flammability such as post-synthetic treatment or integration of fire retardants in the sol gel process have been pursued. Material characterisation was performed using a standardised fire-test setup to evaluate the efficiency of the respective flame retardant approach. Furthermore, mechanical, thermal, chemical and morphological properties were investigated.