Facile synthesis of lanthanum hypophosphite and its application in glass-fiber reinforced polyamide 6 as a novel flame retardant

This work developed flame retarded glass fiber reinforced polyamide 6 (FR-GFPA) composites with excellent mechanical properties, thermal stability and flame retardancy using a novel flame retardant, lanthanum hypophosphite (LaHP). The flame-retarded properties of FR-GFPA composites were characterized by limiting oxygen index, Underwriters Laboratories 94 testing and cone calorimeter test. FR-GFPA composite with 20 wt% LaHP reached V-0 rating and a high LOI value (27.5 vol%). The mechanical performance analysis showed that both the storage modulus and tensile strength increased and then decreased with the increase of LaHP loading. For FR-GFPA composite with 15 wt% LaHP loading, the storage modulus was 164% higher than that of glass fiber reinforced polyamide 6 (GFPA). Thermogravimetric analysis (TGA) and char residue characterization showed that the addition of LaHP can promote the formation of compact physical char barrier, reduce the mass loss rate and thus improve the flame retardancy of FR-GFPA composites.