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

Abstract

Two types of isomeric bi‐DOPO（9,10‐dihydro‐9‐oxa‐10‐phosphaphenan threne‐10‐oxide） flame retardants named DHK（6,6’‐((4,6’‐dihydroxy‐[1,1’‐biphenyl]‐3,3’‐diyl)bis(propane‐3,1‐diyl))bis(dibenzo[c,e][1,2] oxaphosphinine 6‐oxide)） and DMG (6,6’‐((6,6’‐dihydroxy‐[1,1’‐biphenyl]‐3,3’‐diyl) bis (propane‐3,1‐diyl)) bis (dibenzo [c,e][1,2] oxaphosphinine 6‐oxide)） are successfully prepared and their flame retardant properties are investigated. Although they have the same phosphorus content, the corresponding thermoset DHK/Epoxy resins (EP) and DMG/EP show different flame retardancy. The flame retardant mechanism is compared by thermal analysis coupled with Fourier transform infrared (TG‐FTIR), residue FTIR, elemental analysis, Raman spectra, scanning electron microscopy (SEM), and cone calorimetry. More phosphorus remains in the residue of DHK/EP which suggests better‐condensed phase flame retardancy than that of DMG/EP. However, DMG shows a better flame inhibition effect than that of DHK. The results of mean square displacement, free volume fraction, and cohesive energy density in molecular dynamics simulations show that the weakening of the movement ability of the DMG/EP molecular segments should be the reason for the increase in toughness. This shows that although flame retardants possess the same composition, their structure will also affect their flame retardant mechanism and properties, which provide a guide for the design and preparation of high‐efficiency flame retardants.

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.…”

Synergistic Flame Retardant Properties of Polyoxymethylene with Surface Modified Intumescent Flame Retardant and Calcium Carbonate

“…The graphitization degree of the carbon layer is usually indicated by the peak area ratio (I D /I G ) of the D peak to the G peak. Obviously, the smaller the I D /I G value, the higher the degree of graphitization of the carbon layer, which is more beneficial for the surface carbon layer to resist flame burning [ 46 ]. The I D /I G values of P1 and P2 are 0.72 and 0.75 with little difference indicating that Ti-IFR has no contribution to the degree of graphitization of the carbon layer.…”

A DOPO‐based reactive flame retardant containing benzimidazole groups: Synthesis and its flame‐retardation on epoxy resin

“…40,41 The crosslinking degree can be determined through DSC measurement and calculated using Formula (1). [42][43][44][45][46] The heat flow (φ) is obtained by integrating the isothermal DSC curve. The enthalpy (ΔH) of the curing reaction, shown in Figure 4b, is determined by integrating the non-isothermal DSC curve.…”