Rigid polyurethane/expanded vermiculite/melamine phenylphosphate composite foams with good flame retardant and mechanical properties

Expanded vermiculite (EV) was introduced into rigid polyurethane (RPU) foam. The incorporation of 10 wt% EV into RPU foam increases the compressive strength and the flexural strength by 82% and by 115%, respectively compared with untreated RPU foam. The LOI of RPU foam containing 20 wt% EV is only 19.5%. To further improve the flame retardancy of RPU/EV composite foam, melamine phenylphosphate (MPP) was synthesized and introduced into the RPU/EV composite foam. The RPU/EV composite foam with 15% MPP (sample RPU/EV/MPP15) has a LOI of 27.5% and a VO rating in the vertical UL-94 test. The PHRR and THR of sample RPU/EV/MPP15 decrease by 39% and 24%, respectively, compared with the ones of untreated RPU/EV composite foam. The compressive strength and flexural strength of RPU/EV/MPP composite foam gradually decrease with the increase in the amount of MPP. TGA results indicated that the addition of MPP further increase the residue char of the RPU/EV composite foam.