A high‐efficiency DOPO‐based reactive flame retardant with bi‐hydroxyl for low‐flammability epoxy resin

Abstract

A high-efficiency DOPO-based reactive flame retardant (DPE) with bi-hydroxyl was successfully synthesized via reacting DOPO with imine obtained from the condensation of ethanolamine and 1,4-phthalaldehyde, and used as co-curing agent to improve the fire safety of epoxy resin (EP). Its chemical structure was characterized by Fourier transform infrared (FTIR) spectra, 1 H, 31 P nuclear magnetic resonance (NMR) spectra and elemental analysis. The curing behavior, thermal properties, flame-retardant properties of EP/DPE systems were investigated. The results revealed that DPE slightly decreased the glass transition temperature (T g), but accelerated the curing cross-linking reaction of EP. Furthermore, DPE decreased thermal degradation rate of epoxy matrix and promoted the formation of residual char at high temperature. After adding DPE, the flame retardant of epoxy thermosets was greatly improved. Especially, the thermoset modified with 5 wt% DPE achieved limiting oxygen index (LOI) value of 33.6% and V-0 rating in UL-94 test, demonstrating the highly efficient flame retardancy. While its peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) were respectively decreased by 32.6%, 17.8%, and 13.9% compared with neat EP. Moreover, the research on flame retardant mechanism disclosed that DPE played dual flame-retardant effect in the gaseous and condensed phases.

An Effective Method for Preparation of Liquid Phosphoric Anhydride and Its Application in Flame Retardant Epoxy Resin

“…The strong electronegativity of C would reduce the density of electron cloud and the corresponding shielding effect on the shell of P atom, leading to the movement of chemical shift. These results agreed with the previous studies concerning other DOPO derivatives [34,35].…”

A bio-based phosphaphenanthrene-containing derivative modified epoxy thermosets with good flame retardancy, high mechanical properties and transparency

“…This phenomenon has also been reported by the previous papers. 16,20,21 The elemental analysis of FA-bis-DOPO is measured to be 69.0% for carbon, 4.0% for nitrogen, and 13.5% for oxygen. These experimental values are very close to the theoretical values of 69.6% for carbon, 3.9% for nitrogen, and 13.3% for oxygen.…”

A new‐type terephthalonitrile derivative flame retardant of bi‐DOPO compound with hydroxyl and amino groups on epoxy resin

“…This was because stereo-hindrance of DOPO structure in DEZ decreased the crosslinking density of EP. 27 For EP/Ph(CN) 2-5 , the T g (151.1 C) was most than other samples, which was mainly caused by C≡N reacted with epoxy group to increase the crosslinking density.…”

“…The noncombustible gases could also take away a lot of heat when they were released from the EP matrix (Figure 12). 14,27…”