Synthesis of a cardanol-based phosphorus-containing polyurethane prepolymer and its application in phenolic foams

A cardanol-based P-containing polyurethane prepolymer (PPUP), a novel cardanol derivative, was synthesized. Its structure was confirmed by Fourier transform infrared spectrometry and 1H nuclear magnetic resonance. Then phenolic foams (PFs) modified with different contents of PPUP were prepared. The addition of PPUP improves the compressive and specific strengths of the foams, while appropriate addition of PPUP into the resin matrix enhances the specific compressive and flexural strength of PFs. Incorporation of PPUP into PFs leads to a reduced pulverization ratio. The limiting oxygen index increases continuously with the increasing addition of PPUP into PFs. Analysis of thermal decompositions shows that the modified PFs have a similar thermal resistance to pristine foam.