Preparation and Properties of Halogen-Free Flame Retardant Polyurethane Foams
Polyurethane foams (PUFs) filled with several halogen-free flame retardants and composite halogen-free flame retardants were prepared. The flame retardant, thermal stable and mechanical properties of the PUFs were investigated. The results of limiting oxygen index (LOI) and thermogravimetric analysis (TGA) revealed that PUFs filled with dimethyl methylphosphonate (DMMP) had better flame retardancy compared with other flame retardants and DMMP degraded at a low temperature to form several phosphorated acids which accelerated the formation of char layer. Composite flame retardant of DMMP and melamine (MA) had a synergistic effect between phosphorus and nitrogen. The combination of DMMP and MA slightly altered the density of the PUFs. Results from the mechanical analysis revealed that with the increase in concentration of MA in the composite flame retardant of DMMP and MA, the tensile strength of PUFs reduced firstly and then increased up to a constant.