Bifunctional modification of graphene by phosphorus/nitrogen‐containing silane compounds for smoke suppression and flame retardancy of epoxy resins

Abstract

Enhancing the flame retardancy with minimal impact on the mechanical and thermal performances of polymers remains a challenge. This study synthesized a phosphorus/nitrogen‐containing silane compound (D) using polyformaldehyde, KH‐550, and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as raw materials through the Kabachnik‐Fields reaction. After that, D was grafted onto the surface of graphene after hydrothermal treatment to obtain a nano hybrid flame retardant (D‐GR). And D‐GR/EP composites exhibited good flame resistance (LOI = 30.1% and UL‐94 reaches the V‐1 rating) even if the load on D‐GR was 1 wt%. Indeed, the total heat release, the peak heat release rate (PHRR), and the total smoke release of 1% D‐GR/EP dropped by 13.54%, 28.62%, and 44.32%, respectively, in comparison to pure EP. The mechanical performance of 1% D‐GR/EP was effectively maintained, as indicated by the results of impact, tensile and flexural tests. A systematic evaluation indicated that the accession of D‐GR effectively inhibited smoke and heat releases that are ascribed to the synergistic effect of phosphorus/nitrogen‐containing silane compound and graphene. In this study, a facile method was provided for the synthesis of halogen‐free flame‐retardant epoxy composites with superior performances. The combustion products of the as‐prepared composites complied with green and environmental protection standards.

In-Situ Formation of Polynanosiloxane by a Multifunctional Phosphaphenanthrene–Silicone–Epoxy Soybean Oil Flame Retardant Improves the Toughness and Transparency of Epoxy Resin

“…The organophosphorus compounds and their derivatives, recognized for their low toxicity and good thermal stability, have proven effective as halogen-free flame retardants (FRs) for EP. ,− Particularly, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives have attracted significant interest due to their outstanding thermal stability, environmental sustainability, and superior flame-retardant efficacy. − To optimize the flame-retardant efficiency of phosphorus-containing FRs in both gas and/or condensed phases, various additional elements such as nitrogen, silicon, iron, and sulfur have been incorporated to develop highly efficient multiple FRs. − For example, Zhu et al developed a FR using eugenol combined with phosphorus and silicon . Chen et al synthesized a FR curing agent incorporating phosphoric anhydride .…”