Phenolic foam modified with dicyandiamide as toughening agent

Dicyandiamide was used as a toughening agent to modify the brittleness of the phenolic foam. The effects of dicyandiamide on mechanical and flame-retardant properties of phenolic foam were studied by compressive strength, tensile strength, scanning electron microscopy (SEM), UL-94, limited oxygen index (LOI), TG, and cone calorimeter (CONE). The apparent density and SEM results showed that the addition of dicyandiamide can decrease the apparent density of phenolic foam. The compressive, impact test results showed that the incorporation of dicyandiamide into PF dramatically improved the compressive strength, impact strength, indicating the excellent toughening effect of dicyandiamide. The LOI of dicyandiamide-modified phenolic foams remained a high value, and the UL-94 results showed all samples can pass V-0 rating. The modified PF has the slightly lower degradation temperatures but a higher char yield. CONE data indicated that the rate of heat release, total heat release, mass loss rate of the modified PF are decreased compared with that of pure PF, indicating that the modified foams had better flame-retardant performance.