Improvement on fire behaviour of water blown PIR-PUR foams: use of an halogen-free flame retardant

A new flame retardant, i.e. expandable graphite (EG), has been used in polyisocyanurate-polyurethane (PIR-PUR) foams in order to improve fire behaviour of such foams. In order to obtain a completely halogen-free material, water-blown PIR-PUR foams have been prepared thus avoiding the use of hydrochlorofluorocarbons or hydrofluorocarbons. The influence of several EG amounts on physical-mechanical properties and fire performances of such foams has been analysed. The results obtained show that the use of EG affects significantly physical and mechanical properties, such as compression strength and thermal conductivity, particularly at very high EG content (25 wt.%), as it often happens in presence of fillers. The fire performances have been investigated by mean of cone calorimeter apparatus and oxygen index test; the results obtained show that the fire behaviour of PIR-PUR foams could be significantly improved by use of EG; in particular it has observed a dramatically decrease of rate of heat release even for relative low EG amount (15%).