Sustainable flame-retardant polyurethanes using renewable resources

Abstract

Renewable bio resources such as soybean, orange peel, and castor along with a novel phosphorous based polyol were used to prepare highly flame-retardant polyurethane foams. Diethyl allyl phosphonate (DEAP) and thioglycerol (TG) were used to synthesize phosphorous (P) based flame retardant polyol (DEAP-TG). Polyurethane (PU) foams having a various weight percentage of phosphorous were prepared using a varying amount of DEAP-TG (as a phosphorous source) and other bio-based polyols. Use of DEAP-TG polyol in polyurethane foams showed improved compressive strength without affecting closed cell content and morphology of the foams. The horizontal burning test showed a drastic reduction in self-extinguishing time and weight loss for the PU foams containing DEAP-TG polyol. For example, castor oil and DEAP-TG based PU foam which contains 1.5 wt% P showed significant reduction in self-extinguishing time (from 94s to 1.7s) and weight loss (from 48.5% to 3%) compared to neat castor oil based foams. Cone calorimeter data also showed a significant reduction in peak heat release rate, total heat release, total smoke release, and overall smoke production rate for the foam containing 1.5 wt% P compared to 0 wt% P in the foam. The improved flame retardancy was due to the formation of a protective char layer over the surface of the foam due to decomposition of a phosphorus compound. Our research provides a green alternative to prepare industrial grade flame-retardant polyurethane foams.