Flame retarded polyurea with microencapsulated ammonium phosphate for textile coating

Two types of microcapsules of di-ammonium hydrogen phosphate (DAHP) with respectively polyether-polyurethane shell and polyester-polyurethane shell were evaluated as intumescent flame retardant (FR) in a commercial polyurea coating for textiles. The expected advantages of this new concept of encapsulated FR agent are to be compatible with a polymeric matrix in order to give a permanent FR effect and to be itself an efficient FR intumescent formulation for many materials. The thermal degradation for the two types of DAHP microcapsules shows characteristics of an intumescent formulation. The reaction to fire of cotton fabrics coated by FR polyurea loaded with neat or microencapsulated DAHP was studied with the cone calorimeter as the fire model. Both types of DAHP microcapsule present in the polyurea coatings on cotton fabric give an efficient FR effect, although the char developed with microcapsules is a little less heat resistant than that developed with the pure DAHP. Coatings containing microcapsules with polyester-polyurethane shells evolve the smallest quantity of smoke and CO.