A DOPO Derivative Constructed by Sulfaguanidine and Thiophene toward Enhancing Fire Safety, Smoke Suppression, and Mechanical Properties of Epoxy Resin

Abstract

In order to eliminate the negative effect of traditional 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) ‐based flame retardants on heat resistance, mechanical properties, and curing process of epoxy resin (EP), a DOPO derivative (DST) constructed by sulfaguanidine and thiophene is designed and used as co‐cured agent for EP. Compared with EP, the maximum decrease of glass transition temperature (Tg) in all EP/DST samples is less than 5%, indicating EP modified by DST maintains good heat resistance. Encouragingly, DST shows satisfactory flame‐retardant efficiency and excellent smoke suppressing effects. EP containing barely 5 wt% of DST (P content: 0.37 wt%) achieves a UL‐94 V‐0 rating and 32.8% limited oxygen index (LOI) value. Its peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) are also decreased by 31.2%, 18.8%, and 30.2% . Further, DST significantly improves mechanical properties of the EP/DDM/DST system. The tensile strength and modulus increase by 37.2% and 14.6%, respectively, as DST content is 7.5 wt%. It is revealed that DST has positive quenching and diluting effects in the gas phase, as well as promoting the formation of a compact char layer in the condensed phase.

Influence of the Chemical Structure on the Flame Retardant Mechanism and Mechanical Properties of Flame‐Retardant Epoxy Resin Thermosets

“…To compare with the literatures' values, the T g , the tensile strength, PHRR as well as the toughness (impact strength) of previously reported flame retardancy EP are all presented in Figure 10. [25,[48][49][50][51][52][53][54][55][56][57] Based on the above analysis, the DHK/EP and DMG/EP showed flame retardancy and mechanical properties with high glass transition temperature, which showed the practicability of DHK and DMG. However, DHK and DMG showed different mechanical properties and glass transition temperature, which aroused great curiosity.…”

An Itaconic Acid‐Based Phosphorus‐Containing Oligomer Endowing Epoxy Resins with Good Flame Retardancy and Toughness

“…This phenomenon is attributed to the release of phosphorous radicals by the DOPO group in BID during combustion, which interrupted the chain reaction, resulting in incomplete combustion in the gas phase. [42,43] Consequently, due to incomplete combustion of a large number of aliphatic compounds containing carbon, hydrogen and oxygen, total smoke production (TSP) showed an increasing trend. [21,44] Moreover, after CC test results, the amount of char residue of FREP was more than EP, but the magnitude was limited.…”

Esterification Oligomerization of Phosphaphenanthrene Biphenol Caused Efficient Flame Retardant Effect of Group Aggregation in Epoxy Resin

“…14,15 Some DOPO derivatives have been reported as effective flame retardants in epoxy resin. 16 For example, the P−H bond of DOPO can react with a Schiff base, 17 unsaturated double bond, 18,19 and carbonyl group 20 to prepare curing agents of epoxy resins; the additive-type flame retardants were synthesized by combining the phosphaphenanthrene group and other groups with a flame retardant feature. 21−24 In addition, the flame retardancy of some phosphorous polyester compounds prepared by DOPO or its derivatives have been widely studied.…”

“…As one of the efficient flame retardant groups, phosphaphenanthrene group can quench free radical chain reactions in the gas phase during combustion. , 6 H -Dibenz­(C,E)­(1,2)­oxaphosphorin-6-oxide (DOPO) and 2-(6-oxid-6 H -dibenzo­[c,e]­[1,2]­oxaphosphorin-6-yl)-1,4-benzenediol (DOPO-HQ) with phosphaphenanthrene structures have a considerable position in the field of flame retardant polymer materials. , Some DOPO derivatives have been reported as effective flame retardants in epoxy resin . For example, the P–H bond of DOPO can react with a Schiff base, unsaturated double bond, , and carbonyl group to prepare curing agents of epoxy resins; the additive-type flame retardants were synthesized by combining the phosphaphenanthrene group and other groups with a flame retardant feature. − In addition, the flame retardancy of some phosphorous polyester compounds prepared by DOPO or its derivatives have been widely studied. Wang et al used DOPO, paraformaldehyde, diethanolamine, and alkyd resin to obtain flame retarded alkyd resin.…”