Preparation and Performance of Expanded Graphite Added Phosphorus Intumescent Flame-Retardant Epoxy Resins

An intumescent flame retardant composite was prepared by adding expanded graphite(EG) in the 6(4-of DOPO hydroxymethyl phenoxy) cyclotriphosphazene(DOPOMPC) and polyphosphate(APP) treated epoxy resin(EP) system. The effect of EG content on flame retarding properties was studied by limited oxygen index(LOI), UL-94, CONE,TG and SEM, and the retardant mechanism was discussed. The results show that this new type of epoxy resin composites has better flame retardant performance, less smoke and toxicity, and enhanced mechanical properties. The limited oxygen index value could reach to 38.4% for the sample containing 22% DOPOMPC/APP/ EG(DOPOMPC/APP/EG 5/5/1). The CONE experimental results show that pk-HRR, av-SEA, av-EHC and av-CO values of the new composite reduced by 81.8%, 35.5%, 29.0% and 33.3% respectively comparing to that of pure EP, and the tensile strength, flexural strength and impact strength are 70.5%, 1.5 times and 2.6 times higher than that of EP1(10%DOPOMPC/10%APP/EP).