The flame retardant properties and mechanism of the composites based on DOPS and triazine-trione groups in epoxy resin

Abstract

To reduce the risk of fire due to the flammability of epoxy resins (EP), the use of low-cost, non-toxic raw materials for the synthesis of efficient flame retardants is becoming an important research direction in the field of flame retardant technology. This research with tris (2-hydroxyethyl) isocyanurate (THEIC), maleic anhydride (MAH) and 9,10-dihydro-9-oxa-10- phospha-phenanthrene-10-sulfide (DOPS) as raw materials, through esterification reaction successfully synthesised a novel structure of DOPS-triazine-trione flame retardant tris (3-(9,10-dihydro-9-oxa-10-phospha-phenant hrene-10-sulfide)-butanedioic acid monoethyl ester-based) triazine-trione (DOPS-THEIC) and apply it to EP to prepare EP/DOPS-THEIC. The results demonstrate that the incorporation of 12.5 wt% DOPS-THEIC in EP leads to a significant increase in the Limiting Oxygen Index (LOI) value, reaching 32.8 %, which corresponds to achieving a UL-94 V-0 rating. Moreover, the CONE test revealed notable reductions in the peak heat release rate (PHRR), total heat release (THR), and mass loss rate (MLR) values by 74.1 %, 32.4 %, and 52.6 %, respectively, compared to pure EP. These findings indicate that the addition of DOPS-THEIC effectively suppresses the heat release during combustion, attributed to the formation of a char layer that minimizes mass loss and acts as an improved flame retardant in the condensed phase. Furthermore, as the DOPS-THEIC content increased, the EP composites exhibited remarkable retention of their excellent mechanical properties. This observation reinforces the promising potential of DOPS-THEIC as an effective flame retardant for enhancing the fire resistance of EP materials.