Coal fly ash reinforcement for the property enhancement of crude glycerol-based polyurethane foam composites

Coal fly ash(CFA)is the main combustion residue of fine ground coal in the process of coal-fired thermal power generation,and crude glycerol(CG)is the byproduct of biodiesel production.The novel polyurethane/CFA(PU/CFA)foam composites were prepared from CFA and CG.Two kinds of CFA,CFAI and CFAII were used as fillers for the property enhancement of PU/CFA composites,and the effects on foaming behavior and the reinforcement for the PU/CFA composites were investigated.It was found that the addition of CFA can prolong the rising time and tack-free time,and the maximum rising time and tack-free time increased to 40 s and 42 s.Meanwhile,the maximum compressive strength of PU/CFAI and PU/CFAII increased to 0.2186 MPa and 0.2284 MPa with the addition of CFA.The thermogravimetric analysis showed that the PU/CFA composites underwent three stages of thermal decomposition,and the amount of carbon residue increased from 23.11%to 67.91%with increasing CFA dosage.Moreover,the values of the limit oxygen index increased from 21.5%to 23.7%with the incorporation of CFA into the PU foam matrix,indicating that CFA improved the thermal stability and flame retardant performance of the composites.This study provided a new method for the recycling and high-value utilization of CG and CFA.