New developments in chemical modification of fire-safe rigid polyurethane foams

This work reports the preparation of polyurethane-polyisocyanurate (PUR-PIR) foams containing different amounts of flame retardants (FRs) and a layered silicate nanoclay. An environmentally friendly blowing agent, a mixture of 1,1,1,3,3-pentafluorobutane and 1,1,1,2,3,3,3-heptafluoropropane (HFC 365/227), with small amount of water was used. The flame retarded PUR-PIR foams showed better fire resistance in comparison to classical PUR and unmodified PUR-PIR foams without deterioration of their functional properties. It was observed that when nanoclay was used in conjunction with flame retardants containing reactive bromine and phosphorus compounds, and zinc stannate, the flammability was significantly reduced. Expandable graphite was also used in some samples. As control samples for reference purposes three foam systems without any flame retardant were frothed: PUR, PUR-PIR and foams PUR-PIR modified by carbodiimide groups.