Abstract
The effect of different concentrations (4 and 8 wt%) of chemically reactive type flame retardant (FR) chemicals on the thermal stability and flammability of an aerospace grade epoxy resin has been studied by thermal analysis, limiting oxygen index, UL-94, and cone calorimetry. Chemically reactive flame retardant term implies that they interact with the polymer during some part of the pyrolysis and fire chemistries. Flame retardants included (i) phosphorous- and nitrogen-containing, active in condensed phase, (ii) intumescent chemicals, active in condensed phase and also known as char promoters, (iii) organophosphates, active primarily in condensed phase, but in some polymers known to have also shown vapor phase activity, (iv) halogen-containing, active in vapor phase. During curing process some of the flame retardants settled on the bottom of the resin plaque, affecting the flammability results. All FRs reduced the flammability of the resin, the extent of which depended upon the FR type, concentration of flame retardant elements in the formulation and the type of fire testing performed. With selective FRs, carbon fiber-reinforced composites have also been fabricated and tested for their fire and mechanical performance. FR chemicals decreased the flammability of composites up to 50% without affecting their mechanical properties.