Novel flame retardant effects of dopo and poss on epoxy resin

A series of flame retarded epoxy resins (EP) are prepared with a novel polyhedral oligomeric silsesquioxane containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-POSS), OPS (octaphenyl polyhedral oligomeric silsesquioxane) and DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide). The flame retardancy of these EPs are tested by the LOI and UL-94 measurements, indicating that DOPO-POSS has meaningful effects on the flame retardancy of EP composites. 2.5 wt. % DOPO-POSS incorporation into epoxy resin results in a LOI value 30.2 and UL-94 V-1 (t₁ = 8 s and t₂ = 3 s) rating. A very interesting blowing-out effect through the pyrolytic gases spurt are observed in UL-94 test for the EP/2.5%DOPO-POSS. When the mixture of OPS and DOPO, instead of the compound DOPO-POSS, is used in the EP composites, both of them seem to be able to retard synergistically flame of the EP composites, and the more remarkable blowing-out effect is observed. The details of fire behaviors, such as HRR, p-HRR, COPR, and CO₂PR are tested by cone calorimeter. The EP composites with low load of DOPO-POSS and the mixture of OPS and DOPO, respectively, can produce big intumescent char during the cone calorimeter testing. All of experimental results indicate that the blowing-out effect may be determined not only by the releases of pyrolytic gases, but also by the char structure in the condensed phase.