Mechanistic study of thermal behaviour and combustion performance of carbon fibre-epoxy resin composites fire retarded with a phosphorus-based curing system

The fire retardant action in epoxy resins based on tetraglycidyl 4,4'-diamino-diphenylmethane (TGDDM) either alone or combined with the diglycidylether of bisphenol A (DGEBA), cured with bis(m-aminophenyl)methylphosphine oxide (BAMPO) was studied. Comparison of oxygen index (OI) and nitrous oxide index suggests a condensed phase fire retardant mechanism. The yield of the intumescent char continuously increases providing polymer shielding upon increasing the concentration of the fire retardants. In the composite the carbon fibres play the role of inert fillers in combustion in the oxygen index test with, however, fibre orientation having an important effect. The carbon fibres suppress the intumescence behaviour of the char. The chemical mechanism of thermal degradation and charring of the resins is studied using thermogravimetry, thermal volatilisation analysis, char characterisation by FTIR, solid state NMR, X-ray, EPR and elemental analysis. (C) 1996 Elsevier Science Limited