Facile Preparation of a Novel Vanillin-Containing DOPO Derivate as a Flame Retardant for Epoxy Resins

Abstract

A novel bio-based flame retardant designated AVD has been synthesized in a one-pot process via the reaction of 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO), vanillin (VN), and 2- aminobenzothiazole (ABT). The structure of AVD was confirmed using Fourier transform infrared spectroscopy (FTIR), and 1H and 31P nuclear magnetic resonance spectroscopy (NMR). The curing process, thermal stability, flame retardancy, and mechanical properties of the epoxy resin (EP) modified with AVD have been investigated comprehensively. The extent of curing, the glass transition temperature and the crosslinking density of the blend decreased gradually with increasing AVD content. The thermogravimetric analysis (TGA) was used to demonstrate that the presence of AVD reduced the thermal decomposition rate for EP and enhanced the formation of carbon residue during resin decomposition. A blend of 7.5 wt% AVD (0.52% phosphorus) displays a UL-94V-0 rating and a LOI of 31.1%. Reduction of the peak heat release rate, total heat release rate and total smoke production was 41.26%, 35.70%, and 24.03%, respectively, as compared to the values for pure EP. The improved flame retardancy of the flame retardant epoxy (FREP) may be attributed to the formation of a compact and continuous protective char layer into the condensed phase as well as the release of non-combustible gases and phosphorus-containing radicals from the decomposition of AVD in the gas phase. AVD is a new and efficient biobased flame retardant for epoxy with great prospects for industrial applications.

A novel multifunctional phosphorous and nitrogenous reactive flame retardant toward epoxy resins by one‐pot method

“…C1s spectrum was deconvoluted into C C/C H (284.7 eV), C O C (285.6 eV), and C O (289.3 eV) peaks. 28 The peaks at 536.7, 532.8, and 530.8 eV in the O1s spectrum were attributed to COOH, C O P, and P O, respectively. For N1s spectrum, the peaks at 398.4, 400.2, and 403.4 eV were ascribed to pyridine nitrogen, pyrrole nitrogen, and nitrogen oxide.…”

“…For instance, an EP loaded with 7.5 wt% of a novel DOPO-based flame retardant (AND) obtains a UL-94 V-0 rating and 31.3% LOI. 28 Unfortunately, its tensile and flexural strengths reduced by 32.5% and 10.33%, compared with the neat EP. Hence, challenges still remained in developing a novel EP flame retardant with superior comprehensive properties.…”

“…However, flame retardancy has been improved at the price of mechanical performance and transparency. For instance, an EP loaded with 7.5 wt% of a novel DOPO‐based flame retardant (AND) obtains a UL‐94 V‐0 rating and 31.3% LOI 28 . Unfortunately, its tensile and flexural strengths reduced by 32.5% and 10.33%, compared with the neat EP.…”

Thermal Stability and Flame Retardancy of Epoxy Resin with DOPO‐Based Compound Containing Triazole and Hydroxyl Groups

“…[12][13][14][15] There has been reported that the flame-retardant efficiency of DOPO can be further improved through the molecular design method. [16][17][18] Thereinto, introducing the nitrogen-containing group (such as triazine, [19,20] triazinetrione, [21][22][23] Schiff-base, [24][25][26] and hexachlorocyclotriphosphazene [27,28] ) is a feasible way. The phosphophenanthrene group and nitrogen-containing group can exert a P−N synergistic flame-retardant effect to improve the flame retardancy of epoxy thermosets.…”

Thermal Properties and Flammability Characteristics of a Series of DGEBA-Based Thermosets Loaded with a Novel Bisphenol Containing DOPO and Phenylphosphonate Units

“…However, a high content of DOPO groups is required to achieve a significant improvement in the flame resistance of epoxy resins, which can lead to a deterioration of the end-use product’s characteristics. Therefore, the DOPO monomer has been frequently appealed in the synthesis of various flame retardants containing nitrogen, sulfur, silicon, or boron in the structure, elements well-known for their synergistic effect in terms of flame retardancy when used along with phosphorus, thus, showing better flame retardancy in epoxy-resin-based materials [ 15 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. Various diamines and bisphenols containing phosphorus and nitrogen as reactive flame retardants for crosslinking epoxy resin have been reported [ 24 , 25 , 26 , 27 , 28 , 29 ].…”