Study of the synergistic effect of polyhedral oligomeric octadiphenylsulfonylsilsesquioxane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide on flame-retarded epoxy resins

A novel flame retardant additive, polyhedral oligomeric octadiphenylsulfonylsilsesquioxane (ODPSS) has been used to retard combustion of an epoxy resin (EP) of DGEBA (di-glycidyl ether of bisphenol A) with curing agent 4,4′-diaminodiphenylsulphone (DDS). A series of flame-retarded EP was prepared with ODPSS and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) loaded. The flame retardant properties of the EP composites were characterized by the LOI, UL-94 and cone calorimeter test. The EP loading with 2.5 wt.% ODPSS/2.5 wt.% DOPO showed a longer TTI, lower value of p-HRR and higher flammability rating than that loading with 5 wt.% DOPO. The char residues of these EP composites after the cone calorimeter tests were investigated by FTIR and XPS. The thermal stability and pyrolytic gases of the EP composites were detected by TGA-FTIR and DSC. The results indicated that the mixture of ODPSS and DOPO had a remarkable synergistic effect on retarding flame of the EP composites.