Polyhedral oligomeric silsesquioxane hybrided with DOPO and phenylboronic acid for flame-retarded epoxy resin

A new polyhedral oligomeric silsesquioxane (POSS) derivate bearing phenylboronic acid group and 6H-dibenzo[c,e][1,2]oxaphosphinine-6-oxide (DOPO) unit was synthesized and applied in flame retardant epoxy resin (EP). Compared to pure EP, EP/POSS-DOPO-(phenylboronic acid) composites had good transparency and better thermal stability. Micro-scale combustion calorimetry results showed that the addition of POSS-DOPO-(phenylboronic acid) hybrid could greatly reduce the PHRR and THR of EP/POSS-DOPO-(phenylboronic acid) composite. Simultaneously, the UL-94 of EP composite with 7% POSS-DOPO-(phenylboronic acid) achieved V-0 grade and the LOI value increased from 19.4% (neat EP) to 28.6%. Raman spectra results suggested that POSS-DOPO-(phenylboronic acid) hybrid enhanced the formation of residual char with graphitic structure during combustion. Besides, SEM characterization showed that the char of EP/POSS-DOPO-(phenylboronic acid) composite was much more continuous and compact in comparison with that of control samples. Moreover, the mechanical and dielectric properties of EP/POSS-DOPO-(phenylboronic acid) composites have been greatly improved for a better application.

Automated summary

The new POSS-DOPO-(phenylboronic acid) composite showed good transparency and thermal stability in flame retardant epoxy resin, effectively reducing heat release and smoke generation during combustion to enhance fire resistance. Additionally, it increased the thickness of the residual char layer and improved the mechanical and dielectric properties of EP.