Insight into Hyper-Branched Aluminum Phosphonate in Combination with Multiple Phosphorus Synergies for Fire-Safe...

Epoxy resin (EP) has widespread applications in thermosetting materials with great versatility and desirable properties such as high electrical resistivity and satisfactory mechanical properties. At present, 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is widely applied to EP matrix for high flame resistance. Nevertheless, EP/DOPO composites acquire highly toxic decomposition products and smoke particles produced during combustion due to the gaseous fire-inhibition mechanism, which will be a major problem. To address this concern, an effective hyper-branched aluminum phosphonate (AHPP) was rationally designed and then coupled with DOPO into EP matrix to fabricate the fire-safe epoxy resin composites. On the basis of the results, significant increment in limiting oxygen index value (an achievement of 32% from 23.5% for pristine EP) and reduction in peak heat release rate and total heat release (59.4% and 45.6%) with the DOPO/AHPP ratio of 2:1 were recorded. During the cone calorimeter test, both the smoke production and total CO yield of EP-4 composite with the DOPO/AHPP ratio of 1:2 were dramatically decreased by 42.7% and 53.6%, which was mainly associated with the excellent catalytic carbonization of AHPP submicro-particles for EP composite. Future applications of submicro-scaled flame-retardant with various phosphorus oxidation states will have good prospects for development.