Graphene/montmorillonite hybrid synergistically reinforced polyimide composite aerogels with enhanced flame-retardant performance

Polyimide (PI) composite aerogels with enhanced flame-retardant performance have been fabricated with the addition of environmentally friendly flame-retardant additives (i.e. graphene (G) and montmorillonite (MMT)) via an eco-friendly freeze-drying method followed by a thermal imidization process. Through the strong interaction between the two components, graphene oxide/MMT hybrid can be synergistically dispersed in water, providing good dispersibility in PI matrix, thus endowing the composite aerogels with enhanced mechanical, thermal and flame-retardant properties. As a result, the obtained optimal PI/G/M aerogel exhibits a high compression modulus of up to 14.0 MPa, as well as a specific modulus as high as 155.5 MPa cm³ g^-1. Furthermore, with the incorporation of G/MMT hybrids, the decomposition temperature at 10% weigh loss of PI/G/MMT aerogels is 574.3 °C, which is 20 °C higher than that of neat PI aerogels. Moreover, the PI/G/M aerogels exhibit enhanced flame retardant performance with the limiting oxygen index (LOI) value up to 55. Therefore, the G/MMT hybrids synergistically reinforced PI composite aerogels show great potential as high-performance flame-retardant materials.