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.
Piperazine hexahydrate (PI) and diethylenetriamine penta(methylene phosphonic acid) (DTPMP) are used to synthesize flame-retardant PI-DTPMP through supramolecular reaction. The incorporation of PI-DTPMP simultaneously improves the mechanical and flame-retardant properties of epoxy resin (EP). With only 5 wt% loading of PI-DTPMP, EP composites show excellent flame retardancy with a limiting oxygen index (LOI) of 36.4% and V-0 rating in the UL-94 test. The cone calorimetric test results demonstrates that the peak heat release rate, total heat release, and total smoke release of EP/5%PI-DTPMP are reduced by 44.9%, 34.7%, and 37.7% compared with that of neat EP, respectively, owing to the formation of compact and insulating char layer during combustion. Moreover, EP/PI-DTPMP composites show enhanced mechanical properties with the improved tensile and impact strength, as well as higher storage modulus, crosslink densities, and glass-transition temperatures in dynamic mechanical analysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.