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

• In this paper, DOPS and triazine-trione groups are introduced into the same molecular to construct a new efficient flame retardant system through the synergistic effect of double functional groups. • Adding DOPS-THEIC to EP, we found that when DOPS-THEIC was added at 12.5 wt%, the LOI value of EP/DOPS-THEIC increased to 32.8%, achieving a UL-94 V-0 rating. • The PHRR, THR and MLR values of EP/DOPS-THEIC are significantly lower than pure EP, indicating that DOPS-THEIC can effectively inhibit EP's heat release. The char layer produced during combustion reduces substrate mass loss, proving that DOPS-THEIC has good char formation ability. • The flame retardant DOPS-THEIC participated in the curing process of EP composites, forming a variety of cross-linked network structures and improving EP's flexural strength. • The introduction of the S element in DOPO allows the EP to release more sulphur-containing compounds upon combustion, which combine with some water to form strong acids such as sulphuric acid, promoting the dehydration of the substrate into char. 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. [Display omitted] [ABSTRACT FROM AUTHOR]