Synthesis of a DOPO Derivative to Improve the Fire Safety and Mechanical Performance of Epoxy Resin

Abstract

A 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) derivative is prepared. At first, an intermediate 4,4'‐((triazole)bis(azaneylylidene)bis(2,6‐dimethoxyphenol)) (SGA) is obtained from the Schiff‐base reaction between syringaldehyde (S) and 3,5‐diamino‐1,2,4‐triazole (GA). The further product DOPO‐SGA is then introduced into epoxy by blending to improve flame retardancy and mechanical properties. The flammability evaluation is implemented by limited oxygen index (LOI), UL‐94, and cone calorimeter tests. The presence of 3wt.% DOPO‐SGA increases the LOI to 33.2%, upgrades the UL‐94 rating to V‐0, and reduces the release of smoke and heat of epoxy. The tensile strength and impact strength are also enhanced after the introduction of DOPO‐SGA. The addition of 5% DOPO‐SGA increases the tensile strength and impact strength by 47% and 42%, respectively, compared with that of the control EP sample. It is suggested that the mechanical strengthening is ascribed to the ternary cross‐linked network among epoxy monomer, curing agent, and DOPO‐SGA. This work provides a feasible solution to obtain flame‐retardant epoxy resin with enhanced mechanical performance.

Hyperbranched Phosphorus-Containing Benzoxazine for Epoxy Modification: Flame Retardant and Toughening Agent

“…The T g of EP/10@HB2.0 is almost the same as that of EP, which is consistent with the result of crosslinking density, indicating barely sacrificing T g . The comprehensive properties of epoxy resin materials with the flame performance of UL-94 V-0, including the increase in strength (%) and toughness (%), are shown in Figure S5 and compared with the reported literature works. − The results show in the case of the same flame-retardancy level of UL-94 V-0, the epoxy resins in this work show the best comprehensive performance, indicating that HB2.0 is the promising flame retardant and toughening agent.…”

An Organometallic Flame Retardant Containing P/N/S–Cu2+ for Epoxy Resins with Reduced Fire Hazard and Smoke Toxicity

“…The most commonly used halogen-free flame retardants include phosphorus-based flame retardants, nitrogen-based flame retardants, silicon-based flame retardants, metal hydroxides (such as magnesium hydroxide and aluminum hydroxide), boron-containing compounds (such as boric acid and borax), etc. Phosphorus-based flame retardants are regarded as high-efficiency flame retardants due to their efficient fire-retardant properties. − Among the phosphorous compounds, especially those containing 9-10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), their derivatives exhibit excellent flame retardant. , Nitrogenous complexes may be used alone as flame retardants or as additives to other fire retardants (e.g, phosphorus) − to enhance their activity. Though these phosphorus and nitrogen organic flame retardants can effectively enhance the flame-retardant performance of EP, they have less effect on the release of smoke during the burning of EP.…”

“… 7 − 9 Among the phosphorous compounds, especially those containing 9-10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), their derivatives exhibit excellent flame retardant. 10 , 11 Nitrogenous complexes may be used alone as flame retardants or as additives to other fire retardants (e.g, phosphorus) 12 − 14 to enhance their activity. Though these phosphorus and nitrogen organic flame retardants can effectively enhance the flame-retardant performance of EP, they have less effect on the release of smoke during the burning of EP.…”

A Boron‐Containing Ammonium Polyphosphate for Epoxy Resins with Enhanced Flame Retardancy and Reduced Smoke Release

“…[4] The most convenient solution to increase the fire safety of EP is to blend flame retardants with epoxy monomers and curing agents before curing. [5,6] Halogen-containing chemicals will bring negative effects to the environment and human health, [7][8][9][10] therefore, many P/N-containing flame retardants have been developed to replace them [11] in the past decades. Ammonium polyphosphate (APP) has been documented as an effective flame retardant for many kinds of polymers including EP, [12,13] but no less than 15% APP is required to achieve an ideal flame-retardant level, [14][15][16][17] which usually brings obvious mechanical loss.…”