Effect of phosphorus‐containing flame retardants on flame retardancy and thermal stability of tetrafunctional epoxy resin

Hexaphenoxycyclotriphosphazene (HPCTP) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) were used to flame retardN,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane epoxy resins. The curing behaviors and glass transition temperature were investigated by differential scanning calorimetry. The limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests were used to assess the flame retardancy of the cured epoxy resins. The increase in LOI value and UL‐94 rating was strongly dependent on the phosphorus content. The reduction in peak of heat release rate and total heat release showed that the incorporation of flame retardants could improve the flame retardancy of epoxy resin. The higher smoke release and CO yield of the flame‐retardant epoxy resins indicated that both DOPO and HPCTP showed a gas phase flame retardancy action. Thermogravimetric analysis of the flame‐retardant epoxy resins indicated that the incorporation of the flame retardants reduced the initial decomposition temperature of epoxy resin. Copyright © 2015 John Wiley & Sons, Ltd.