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

ABSTRACT 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 CO 2 ) 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.