The Synergistic Effect of Bio-Based Cobalt Alginate via Facile Preparation on the Intumescent Flame-Retardant Epoxy Resin

Green bio-based flame retardants are becoming increasingly popular due to environmental concerns and the use of petroleum resources. Here, cobalt alginate (CA) was prepared and used as a charring agent with catalytic action in epoxy resin (EP)/ammonium polyphosphate (APP) to improve flame retardance. The results show that CA and APP in EP have great synergistic effects on enhancing charring and preventing melt dripping. EP/14 wt% APP cannot pass any UL-94 rating, while the composite with 0.1 wt% CA can easily reach V-0. The V-0 grade can still be attained even if the total additive amount for EP/APP/CA is reduced by 2 wt%. The maximum limiting oxygen index of EP/APP/CA was 28.8%, which was 7.9% higher than that of EP/APP. Besides, its heat, smoke, and harmful gases (CO and CO2) release were obviously diminished. In comparison with EP/APP, the fire hazard of EP/APP/CA was obviously reduced and the thermostability at high temperatures was greatly improved. Moreover, EP/APP/CA has superior carbon formation, which was because CA acted as a charring agent, and good catalytic role of its cobalt element. This study provides inspiration for using marine biomass as green flame-retardant fillers.