Layer-by-Layer Assembly of Hollow Glass Microspheres Using Branched Polyethyleneimine for Thermally Insulating and Flame-Retardant Glass Fiber Reinforced Composites
Glass fiber reinforced polymers (GFRP) are attractive structural materials exhibiting thermal insulation due to their low thermal conductivity and high strength to weight ratio. Conventional insulation enhancement of GFRP by dispersing hollow glass microspheres (HGM) in the resin often induces filtration effects and viscosity increase, hindering resin impregnation and composite quality. To address this limitation, a layer-by-layer assembly approach was used to deposit HGM onto fibers. Branched polyethyleneimine imparted positive surface charges to the fibers, enabling electrostatic adsorption of negatively charged HGM. The coating density was controlled by the number of bilayers without impairing resin flow. Consequently, the composites achieved a 42% reduction in thermal conductivity at three bilayers and improved flame retardancy, evidenced by reduced heat release and delayed ignition.