Fire behaviour and mechanical properties of an epoxy hot-melt resin for aircraft interiors

This study focuses on an epoxy novolac-based hot-melt prepreg resin system cured with dicyandiamide for purpose of aircraft interiors. The influence of the phosphorus-based reactive flame retardant 9,10-dihydro-9-oxa-10-phos-phaphenanthrene-10-oxide (DOPO) as a function of its concentration on the flammability behaviour of the cured neat resin is investigated by UL 94 testing. Besides this, the efficiency of boehmite as synergistic flame retardant is examined at two levels of DOPO content. The effect of the specific flame retardants on the mechanical properties of the cured resin formulations is evaluated by tensile and fracture toughness testing. Glass transition temperatures are measured using dynamic mechanical analysis. It is shown that the flame retardancy is significantly improved with increasing phosphorus content whereas the glass transition temperature decreases. The fracture toughness is not affected within the considered range of phosphorus content. The addit ion of boehmite to the modified resins leads to further improvement in flame-retardant behaviour. Moreover, it is presented that the fracture toughness increases with higher content of this mineral microfiller while the elongation at break is not lowered for boehmite loadings up to approximately 25 wt.%.