There have been a number of review papers on layered silicate and carbon nanotube reinforced polymer nanocomposites, in which the fillers have high aspect ratios. Particulate‐polymer nanocomposites containing aerogel with extremely low density, large open pores, and high surface area are also an important class of polymer nanocomposites. Thus, this article provides an overview on the effect of aerogel on mechanical and thermal properties of polymer‐based nanocomposites. Moreover, the preparation, history, classification, and characteristics of the aerogel are addressed. Among the polymer‐aerogel nanocomposites, various categories including silica and carbon aerogel‐polymer nanocomposites were discussed in detail. POLYM. COMPOS., 39:3383–3408, 2018. © 2017 Society of Plastics Engineers

Silica aerogel is a promising candidate for improving the mechanical properties of epoxy-based nanocomposites due to the unique properties such as the 3-dimensional nanoporous structure and high surface area. In this study rheological, mechanical and thermal properties of the silica aerogel-epoxy nanocomposites were investigated. The rheological results demonstrated an increase in viscosity of the nanocomposite suspension compared to the neat resin. The results of dynamic mechanical along with the thermal analysis showed that the addition of 6 wt% of silica aerogel causes the storage modulus and glass transition point (Tg) to be increased by 11% and 5 °C, respectively. Also, significant improvements in the elastic modulus (35%), tensile strength (62%) and toughness (126%) were achieved with the optimal volume fraction of silica aerogel (6 wt%). Two main fracture mechanisms were involved in the fracture behavior of the silica aerogel-epoxy nanocomposite: (a) crack pining and deflection, and (b) plastic deformation (debonding).

Polymer nanocomposites reinforced with inorganic fillers have sparked new aerospace, sports goods, automotive, and civil engineering applications. Here, epoxy nanocomposites with both hydrophobic and hydrophilic silica aerogel powder fillers are presented. The use of a high porosity, mesoporous filler such as silica aerogel avoids the typical problems encountered in dispersing nanoparticles. For both types of aerogel surface chemistry, the addition of minor amounts of silica aerogel leads to a strong increase of application relevant properties, e.g., fracture toughness and energy, impact strength, T g , and storage modulus. The strong covalent silica−epoxy interactions seen for the hydrophilic filler, but absent for the hydrophobic filler, are reflected in the bulk properties. Detailed fractography reveals three active toughening mechanisms: (i) an increase in nanoscale fracture roughness, (ii) crack front bowing and deflection, and (iii) the formation of shear bands. The industrial availability of silica aerogel powders, the excellent properties, and the ease of preparation of the epoxy composites make silica aerogels exceptional nanoporous fillers for polymer reinforcement.