Synthesis and fire properties of rigid polyurethane foams made from a polyol derived from melamine and cardanol

Abstract

In this work, a melamine and cardanol-derived Mannich base polyol (MCMP) was synthesized via a two-step process. First, cardanol was allowed to react with paraformaldehyde melamine and diethanolamine to yield mixed Mannich bases which were subsequently propoxylated to give the MCMP. Rigid polyurethane foams (RPUFs) were prepared using MCMP and a polyisocyanate. Effects of expandable graphite (EG), ammonium polyphosphate (APP) and diethyl ethylphosphate (DEEP) on the flame retardancy, mechanical properties, thermal stability and morphology of the resultant RPUFs were studied. It was demonstrated that the melamine incorporated into the MCMP molecular structure increased the thermal stability and the flame retardancy of the RPUF. The fire resistance of the foam could be further enhanced by the addition of flame retardants. EG is more effective than APP and DEEP in enhancing the limiting oxygen index of MCMP-based RPUFs. The flame-retardant-filled RPUFs display a better compressive strength, thermal stability, char residue, heat release and smoke emission than does the non-filled foams.