Sustainable bacterial cellulose-based composite aerogels with excellent flame retardant and heat insulation

Bacterial cellulose (BC) aerogels with ultralight, low density, and low thermal conductivity are hopeful candidates for environmentally friendly heat insulating materials. However, the application of BC in packaging and building as a heat nonconductor is seriously limited by its flammable characteristics. Hence, we report a moderate approach to fabricating a flame retardant and heat-insulating composite aerogel by introducing zinc borate (ZnB) particles into BC via an ultrasound-assistant deposition process. The in situ synthesis of ZnB particles resulted in the separation of single fibers from fiber bundles in BC instead of damaging its homogeneous porous structure, improving its thermal stability by weakening the convective intensity of heat rays. The heat release capacity of the prepared composite aerogel was only 8 J g −1  k −1 , exhibiting excellent flame retardancy. The probable mechanism proposed to be that the dehydration of ZnB particles lowered the surface temperature by releasing the bound water, and simultaneously produced metallic oxides (ZnO and B 2 O 3 ) for retarding the spread of heat and isolating the flammable fibrils within the combustion area. Besides above scientifical meaning on understanding the thermal insulation process, because of the natural and renewable substrate and the following simple modification process, the present approach has potential applications for industrial-scale production of green and flame retardant material.