Mechanical, thermal and flammability properties of glass fiber film/silica aerogel composites Congcong Li, Xudong Cheng, Zhi Li, Yuelei Pan, Yajun Huang, Lunlun Gong ⁎ State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China abstract article info Article history: Received 8 September 2016 Received in revised form 13 November 2016 Accepted 16 November 2016 Available online xxxx Aerogels are the best thermal insulating materials ever known because of their extremely low thermal conduc- tivity. However, their applications are limited because of their brittleness and low strength. For maintaining the integrity, we prepared glass fiber film reinforced silica aerogel composites have been prepared by the sol–gel method via ambient pressure drying. The composites were characterized by scanning electron microscopy, bulk density analysis, Brunauer–Emmett–Teller method, thermal constant analysis, and compression and cone calorimeter tests. The H 2 O: TEOS molar ratio of the silica aerogels was found to affect the properties of the com- posites significantly. As the H 2 O: TEOS molar ratio increased from 2 to 6, the density of the composites first de- creased dramatically and then increased slightly. The thermal conductivity also showed the same trend. The mechanical properties of the composites were improved greatly compared to the pure aerogels without compromising their thermal insulation properties. Moreover, the composites prepared in this work exhibited more elasticity and flexibility than the conventional thermal insulating materials. The data obtained from the cone calorimeter test showed that with an increase in the H 2 O: TEOS molar ratio, the fire hazard of the compos- ites decreased. © 2016 Elsevier B.V. All rights reserved. Keywords: Aerogel composites Glass fiber films Mechanical properties Thermal insulation Flammability 1. Introduction Recently, energy-saving thermal insulation materials have attracted immense attention. Particularly, fireproof thermal insulation materials with high efficient thermal insulation are gaining attention and have promising prospects in the field of heat insulation [1–3]. Silica aerogels are ultralight materials with a three-dimensional network of intercon- nected nanometer-sized primary particles. Owing to their remarkable characteristics, such as low density (0.003–0.5 g cm -3 ), high porosity (80–99.8%), high specific surface area (500–1000 m 2 g -1 ), and ex- tremely low thermal conductivity, typically of the order of 0.005– 0.015 W m -1 k -1 [4–6], Silica aerogels are regarded as the best thermal insulating materials ever known. However, because of high porosity, they exhibit poor mechanical properties, such as low strength, poor toughness and brittleness. This seriously limits their practical applications Several methods have been used to improve the mechanical proper- ties of silica aerogels [7–9]. One of the most convenient and effective methods is the addition of fibers to the silica sols as supporting skele- tons, resulting in the formation of fiber reinforced aerogel composites [10]. Various fibers such as ceramic [11,12], mullite [13], glass [14,15] and aramid fibers [16] can be combined with aerogel for reinforcement. Although aramid fibers exhibit good mechanical properties, the organic components in these fibers may contribute to combustion. Inorganic glass fibers, which exhibit high mechanical strength and are non-com- bustible, heat insulating, and corrosion resistant, have been widely used. It has been reported that the introduction of fibers in aerogel in- creases their thermal conductivity [13,17]. The increase of thermal con- ductivity is a disadvantage to the thermal insulation performance of the aerogel composites. A cheaper, simpler, and safer method to introduce glass fibers into aerogel composites is to handle the glass fibers with a carding machine. The resulting films are lighter than blankets and can reduce the contact between the fibers and the thermal conductivity of the composites. Moreover, reducing the effective pore size is an efficient method to suppress the heat transfer in silica aerogels. The molar ratio of water to silica precursors plays an important role in controlling the nanostructure of silica aerogels. Therefore, in this study, we investigated the effect of H 2 O: TEOS molar ratio (S) on the thermal conductivity and mechanical properties of GF/aerogel composites. Currently, the introduced hydrophobic organic groups during the preparation of silica aerogels are inevitable for acquiring the hydropho- bicity. These organic components just contribute a potential fire risk to silica aerogels exposed to a heat flux or other flame propagating mate- rials in an existing fire. However, the flammability of hydrophobic silica aerogels has been neglected till date and a very limited literature is available to discuss the fire reaction properties and burning behavior of SA composites under radiation. It is generally believed that the heat Journal of Non-Crystalline Solids 457 (2017) 52–59 ⁎ Corresponding author. E-mail address: gongll@mail.ustc.edu.cn (L. Gong). http://dx.doi.org/10.1016/j.jnoncrysol.2016.11.017 0022-3093/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol