Thermal behaviour and fire and mechanical performance of carbon fibre-reinforced epoxy composites coated with flame-retardant epoxy gelcoats

Abstract

We investigated the industrial applicability of multifunctional flame-retardant epoxy gelcoats based on flame retardants containing phosphorus (P), in particular ammonium polyphosphate (APP, which acts in the solid phase), resorcinol bis(diphenyl phosphate) (RDP, which mainly acts in the gas phase) and their combination. It was possible to apply most of the formulations via spraying with the use of a diluent, while gelcoats containing RDP were sprayable without a diluent. The presence of both flame retardants provided excellent fire performance, while the Shore D hardness of the gelcoats decreased significantly, which is favourable in terms of flexibility. We compared the effect of the composite (wet compression moulding and vacuum infusion) and gelcoat manufacturing (brushing and spraying) technologies on fire behaviour. Both vacuum infusion and spraying significantly decreased the peak heat release rate and the total heat release of the coated samples during the mass loss type cone calorimetry tests. The composites prepared by vacuum infusion and coated by spraying showed the best overall fire performance. Heat release rates, three-point bending test results and the dynamic mechanical analysis of the coated samples revealed that the flame retardancy of the composite base itself can be omitted.