(267c) Fire Retardant Fatty Acid Based Vinyl Ester Resins

One method of reducing styrene emissions from vinyl ester (VE) resins is to replace some of the styrene with methacrylated fatty acid monomers. For some applications, it is important not only to reduce hazardous air pollutant contents by using fatty acid monomers, but also to have fire retardancy. Common practices for providing fire retardancy in polymers involve the use of halogenated species, while a newer method uses polyhedral oligomeric sil sesquioxanes (POSS) additives. Rather than using brominated vinyl ester monomers, a brominated fatty acid based monomer, 9-10 di-bromo stearic acid glycidyl methacrylate, was synthesized from oleic acid and used as a partial replacement for styrene in vinyl ester. The brominated fatty acids increased the resin viscosity relative to styrene-based and non-brominated fatty acid-based resins. As a result, the vinyl ester content was lowered from 55-65 wt% to 40-50 wt% to produce resins with low enough viscosities for composite liquid molding processes. Thermal and mechanical properties were thereby reduced. As a result, Novalac vinyl esters were used instead of bisphenol A vinyl ester monomers, which increased glass transition temperature (Tg) by 5-10°C. Rather than using halogen-based fire retardants, a methacrylated POSS additive (FireQuench 1284) was blended into fatty acid vinyl ester resins. The POSS additive similarly increased the viscosity and decreased Tg. The POSS methacrylate additive was ineffective in reducing flammability at contents of 1-30 wt%. On the other hand, the brominated fatty acid monomers were very effective in improving fire-retardancy in vinyl ester resins. Thermogravimetric analysis showed that brominated resins are effective in reducing flammability because of the low breakdown temperature of the bromine-carbon bond, which creates bromine radicals that reduce oxygen and hydrogen concentrations, thereby helping to extinguish the flame.