Preparation of a multifunctional flame retardant epoxy resin containing phosphorus and nitrogen and study of its properties

Abstract

A highly reactive intrinsic epoxy flame retardant FREP was successfully synthesized via ring‐opening reaction between DOPO and amino‐tetrafunctional epoxy resin (AG‐601), and the structure of the synthesized FREP was characterized by FTIR and MS. FREP was then introduced into the epoxy resin as an additive, aiming to improve fire safety. The flame‐retardant properties and thermal stabilities of epoxy thermosets were investigated by limiting oxygen index (LOI), vertical burning test (UL94) and cone calorimetry (CONE). The results indicated that EP/FREP‐4 thermoset passed UL94 V‐0 rating with a LOI value of 34.6%, where the phosphorus content was 1.5 wt%. When compared with neat EP, the peak heat release rate (pk‐HRR), total heat release (THR) and total smoke production (TSP) decreased by 63.1%, 42.6%, and 22.1%, respectively. Meanwhile, the lower av‐EHC of EP/FREP thermosets indicated that FREP plays a significant role in gas‐phase flame retardancy. Additionally, DMA analysis showed that FREP improved the crosslinking density of EP, which had little effect on the glass transition temperature (Tg). Thermogravimetric analysis (TGA), Py‐GC/MS analysis, and SEM were used to investigate the flame retardant mechanism. Excellent flame retardancy was attributed to phosphorus and nitrogen's synergistic effect in the gas and condensed phases.

A novel epoxy resin system containing bismaleimide and DOPO‐based flame retardant with excellent flame retardancy and toughness

“…FREP was synthesized by reacting AG‐601 with DOPO in a 1:2 molar ratio. The synthesis method was described in the previous reference, 27 and the reaction principle was shown in Scheme 1. DOPO was grafted onto the AG‐601 molecule through a ring‐opening reaction with the epoxy group via a PH bond.…”

“…In earlier research, we created a reactive flame retardant named FREP by chemically bonding DOPO to the molecular chain of AG‐601, which was then introduced to DGEBA to improve its flame‐retardant property 27 . On this basis, to handle the brittleness and flammability of EP, we doped BDM into DGEBA and FREP, cured by diaminodiphenylmethane (DDM).…”

“…In earlier research, we created a reactive flame retardant named FREP by chemically bonding DOPO to the molecular chain of AG-601, which was then introduced to DGEBA to improve its flame-retardant property. 27 On this basis, to handle the brittleness and flammability of EP, we doped BDM into DGEBA and FREP, cured by diaminodiphenylmethane (DDM). The structure of this flame retardant epoxy system was characterized, and its flame-retardant property and mechanism, thermostability, and mechanical property were explored more thoroughly.…”

Synthesis of bio‐based reactive N/P flame retardant and its curing and flame retarding behavior in epoxy resins

“…The preparation of HAPV‐EP composite and the flame retardant mechanism is shown in Figure 1. Flame retarding mechanism of the HAPV/EP was systematically studied by TGA‐FTIR (FTIR is defined as Fourier Transform infrared spectroscopy) and char analysis using Raman spectra, scanning electron microscopy (SEM), and x‐ray photoelectron spectroscopy (XPS) 18 . It provides a new direction for the preparation of bio‐based EP flame retardants.…”