SYNOPSISThe study, by scanning and transmission electron microscopy ( SEM and TEM ) , of the morphological aspects of thermal degradation of poly ( phenylene ether) -high-impact polystyrene blends (PPE/HIPS) occurring on burning gives a detailed mechanistic insight into the process. It is seen that thermal degradation leads to a cellular structure in the material that evolves to a foamed char on burning. The fire-retardant triphenyl phosphate can modify the shape and size of the cellular structure.

ABSTRACT:The thermal and flame-retardant properties of phenol-formaldehyde-type resins (crosslinked and noncrosslinked) in mixtures with triphenyl phosphate and styrene-acrylonitrile resins were evaluated. The mixtures show a synergistic effect between triphenyl phosphate and novolacs. Those containing phenol-formaldehyde novolac resins are found to be most flame retardant. There does not seem to be a relationship between the oxygen index (OI) and UL 94 tests. Scanning electron microscopy analysis show a surface structure with cavities and stratification, very similar to that of intumescent additives. Evidence was found indicating that this flame-retardant system works in both the gas and condensed phase.