Synthesis of low phosphorus flame retardant containing benzimidazole and hydroxyl and its application in reducing combustion smoke for epoxy resin

Abstract

Abstact In this work, an economic and environmentally friendly phosphorus‐nitrogen‐based flame‐retardant containing benzimidazole structure and hydroxyl group (DOPO‐BHM) was successfully synthesized by a simple two‐step procedure. The as‐prepared DOPO‐BHM was characterized by 1H NMR, 31P NMR, and FTIR, and incorporated into epoxy matrix as co‐curing agent to remarkably improve the flame retardancy of epoxy resin (EP). When the amount of DOPO‐BHM in EP was 6% and the phosphorus content was as low as 0.408%, the EP/DOPO‐BHM composites achieved a high limiting oxygen index (LOI) of 32.7% and V‐0 vertical firing grade. Furthermore, the cone calorimeter (CC) test results showed that the values of total heat release (THR), heat release rate (HRR), total smoke production (TSP), and smoke production rate (SPR) of EP/6% DOPO‐BHM decreased by 12.9%, 28.5%, 30.0%, and 47.8% relative to EP, respectively, indicating that the modified EP had good performance of reducing heat release and inhibiting smoke release. In addition, FTIR, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) were carried on to understand the flame retardancy mechanism. The characterizations indicated that the flame retardancy effect of DOPO‐BHM was in both condensed and gaseous phase, and gaseous phase played a dominant role. In addition, the mechanical test results showed that the tensile strength, bending strength, and non‐notched impact strength of EP/6% DOPO‐BHM were improved to a certain extent. In summary, DOPO‐BHM could significantly improve the flame retardant effect of EP without loss of mechanical properties and reduce emissions of phosphorus and smoke.

P/N Flame Retardant Based on a Pyrimidine Ring for Improving the Flame Retardancy, Mechanical Properties, and Smoke Suppression of Epoxy Resin

“…The EP demonstrated a UL-94 V-0 rating and 28.5% limited oxygen index (LOI) value with the addition of 5 wt % HTACP, and the results of the cone calorimetric test further demonstrated the outstanding smoke suppression effect that HTACP provided. Wang et al synthesized an economical and environmentally friendly phosphorus–nitrogen-based flame retardant (DOPO-BHM) containing a benzimidazole structure and a hydroxyl group and incorporated it into the EP as a curing agent. The LOI value of the modified EP climbed to 32.7% and exhibited a UL-94 V-0 rating with the addition of 6 wt % DOPO-BHM.…”

Flame-Retardant Properties and Mechanism of Polylactic Acid-Conjugated Flame-Retardant Composites

“…The addition of flame retardants is a common method for improving the flame retardancy of PLA, and there are many types of flame retardants suitable for PLA ( Tawiah et al, 2018 ). Among them, organophosphorus compounds and their derivatives have received extensive attention because of their excellent flame retardancy and non-toxicity ( Hirsch et al, 2017 ; Salmeia et al, 2018 ; Nazir and Gaan, 2020 ), and their applications are very broad ( Wu et al, 2018 ; Bascucci et al, 2022 ; Wang et al, 2022 ).…”

A phosphaphenanthrene‐based derivative for simultaneously improving flame retardant and smoke suppression of epoxy resin composites

“…[9][10][11][12][13] Organophosphorus compounds, have drew the attention of many scholars thanks to high efficiency and low toxicity, which it works on condensed phase through promoting charring and gaseous phase through fire inhibition. [14][15][16][17][18][19] Lately, DOPO have become research hot benefited by its flexible structure designability and high flame-retardant activity. 20 The P H bond of DOPO structure is very lively and it react with carbonyl, epoxy group, double bond and other unsaturated bonds to synthetize different flame retardant.…”

“…Organophosphorus compounds, have drew the attention of many scholars thanks to high efficiency and low toxicity, which it works on condensed phase through promoting charring and gaseous phase through fire inhibition 14–19 . Lately, DOPO have become research hot benefited by its flexible structure designability and high flame‐retardant activity 20 .…”