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To alleviate the fire hazard of epoxy resin (EP), an efficient flame retardant (ADM) containing phosphophenanthrene and thiazole groups is synthesized and used as co-curing agent for 4,4′-diaminodiphenyl methane to prepare EP/ADM composites. EP/4 mass% ADM composites with phosphorus content of only 0.25 mass% reach UL-94 V-0 rating and the limiting oxygen index value is high to 35.8%. The results reveal that the peak heat release rate, total smoke production, and total heat release of EP/4 mass% ADM composites are reduced by 24%, 14.4% and 16.7%, respectively, in comparison with those of pure EP. The improvement in flame retardancy is mainly attributed to the decomposition of DOPO which produces HPO• and PO• to capture the reactive radicals in the gaseous phase. The thiazole group releases hindered amine groups and inactive gas with a dilution effect in the gaseous phase thus further enhancing the effect of the phosphophenanthrene group. Besides, ADM helps to increase the glass transition temperature (Tg) of EP/ADM composites, which is 176 °C for EP/4 mass% ADM composites, which is higher than the value (172 °C) of EP. [ABSTRACT FROM AUTHOR]

One of the current challenges in the development of flame retardants is the preparation of an environmentally friendly multi-element synergistic flame retardant to improve the flame retardancy, mechanical performance, and thermal performance of composites. This study synthesized an organic flame retardant (APH) using (3-aminopropyl) triethoxysilane (KH-550), 1,4-phthalaadehyde, 1,5-diaminonaphthalene, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as raw materials, through the Kabachnik-Fields reaction. Adding APH to epoxy resin (EP) composites could greatly improve their flame retardancy. For instance, UL-94 with 4 wt% APH/EP reached the V-0 rating and had an LOI as high as 31.2%. Additionally, the peak heat release rate (PHRR), average heat release rate (AvHRR), total heat release (THR), and total smoke produced (TSP) of 4% APH/EP were 34.1%, 31.8%, 15.2%, and 38.4% lower than EP, respectively. The addition of APH improved the mechanical performance and thermal performance of the composites. After adding 1% APH, the impact strength increased by 15.0%, which was attributed to the good compatibility between APH and EP. The TG and DSC analyses revealed that the APH/EP composites that incorporated rigid naphthalene ring groups had higher glass transition temperatures (Tg) and a higher amount of char residue (C700). The pyrolysis products of APH/EP were systematically investigated, and the results revealed that flame retardancy of APH was realized by the condensed-phase mechanism. APH has good compatibility with EP, excellent thermal performance, enhanced mechanical performance and rational flame retardancy, and the combustion products of the as-prepared composites complied with the green and environmental protection standards which are also broadly applied in industry. [ABSTRACT FROM AUTHOR]

• Mn 3 CoO x was prepared to enhance the fire safety of epoxy resins (EP). • Mn 3 CoO x impressively reduced pHRR and pSPR by 47.5 % and 34.6 %, respectively. • Mn 3 CoO x can effectively catalyze the transformation of hazardous gases. • Recovery of Mn 3 CoO x to 90.0 % in EP composite. The development of metal oxide flame retardants that are easy to synthesize, efficient, and recyclable would be more beneficial to circular economy. In this work, a porous core-shell Mn 3 CoO x was developed to efficiently reduce heat, smoke as well as hazardous gas during the combustion of epoxy resin (EP). Compared with pure EP, the peak heat release rate (pHRR), total heat release (THR), peak smoke production rate (pSPR), total smoke production (TSP), peak CO production rate (pCOPR), and peak CO 2 production rate (pCO 2 PR) of EP/Mn 3 CoO x are reduced by 47.5 %, 21.5 %, 34.6 %, 17.6 %, 58.6 %, and 55.4 %, respectively. It has been shown that Mn 3 CoO x not only catalyzes the formation of high-quality char layer but also effectively catalyzes the conversion of hazardous gas products into CO 2. Recovery experiments of Mn 3 CoO x filler in EP composites show that the recovery of Mn 3 CoO x can reach 90.0 %. This work provides insights into the design of efficient metal oxide flame retardants and ideas for the development of recycled flame retardants. [Display omitted] [ABSTRACT FROM AUTHOR]

• A bio-based flame retardant (FDI) was synthesized for epoxy resin. • FDI endows EP with excellent flame retardancy and low dielectric properties. • The introduction of FDI significantly improved the toughness of epoxy resin. The development of high-performance EP composites with high glass transition temperature (T g), excellent flame retardancy, and UV resistance is a challenging topic in the flame retardancy community. In this work, a bio-based phosphorus/nitrogen/sulfur (P/N/S) containing flame retardant (FDI) was prepared from furfural, 2-amino-5-nitrothiazole, and DOPO. It was applied to improve the flame retardant, dielectric, and UV-resistant properties of EP. Thanks to the combination of phosphorus, nitrogen, and sulfur in FDI, the EP/FDI composites showed superior flame retardancy. Only adding 5 wt% FDI made EP achieve UL-94 V-0 flammability rating with a limiting oxygen index (LOI) of 27%. Meanwhile, EP/FDI-5% composite showed significant reduction of 65.1% and 33.6% in total smoke production (TSP) and the peak heat release rate (pHRR), respectively. The flame-retardant mechanisms of EP/FDI thermosets were investigated by residual char photographs, SEM, XPS, and Py/GC-MS. Moreover, compared to pure EP, EP/FDI composites showed excellent UV resistance, low dielectric properties, and high glass transition temperature, which was expected to be extensively used in multiple areas of production. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cubic metal organic flame retardant with single crystal structure and rich in nitrogen was synthesized by hydrothermal method. • The peak heat release rate of EP composite loaded with 9 phr R1-MOF decreased by 51.3%. • Flame retardant shows high flame retardancy and smoke suppression performance, and significantly reduces the toxicity of EP. • Synergistic flame retardancy between N element and metal ions in metal organic framework ligands. Toxic substances released during the combustion of epoxy resin (EP) not only cause casualties, but also pollute the environment. Hence, aiming at the flammability of EP, a new triazine based metal organic framework (R1-MOF) was successfully synthesized by solvothermal method to reduce the fire resistance of EP. The single crystal structure of MOF was determined by X-ray single crystal diffraction, and the regular hexahedral structure of the crystal was determined by scanning electron microscope. The peak heat release rate, smoke generation rate, CO generation and CO 2 generation of EP composite loaded with 9 per 100 parts of matrix resin (phr) of R1-MOFs were decreased by 51.3, 41.5, 45.3, and 39.1%, respectively, showing high flame retardancy and smoke suppression performance, and significantly reducing the toxicity of EP. It mainly benefited from the flame retardant N element in MOF ligand and the synergistic effect between ligand and metal ions. In this study, a new type of MOF flame retardant was proposed, which provided a new way to design efficient flame retardants, smoke suppressants and detoxification flame retardants. [ABSTRACT FROM AUTHOR]

A multi-functional kaolinite-based compound (AST@Kaol) was prepared by successive loading of TiO 2 and SiO 2 to the surface of metakaolinite (Kaol), followed by reaction with γ-aminopropyl triethoxysilane (APTES). The hybrid was then introduced to epoxy resin (EP) to enhance flame retardancy, smoke suppression and anti-aging properties. The results demonstrated the presence of only 3 wt% AST@Kaol can increase the value of limit oxygen index (LOI) of EP composite to 27.3% from 25.3% of neat EP, as well as decrease the value of heat release rate, total smoke release and the smoke density by 36.9, 14.3 and 19.9%, respectively, compared to neat EP. Besides, the thermal stability and thermal oxidative resistance of EP composites was enhanced. The mechanism of fire retardancy, anti-ageing and mechanical of the EP composite containing AST@Kaol was also speculated. [Display omitted] •A kaolinite-based compound (AST@Kaol) was prepared by co-precipitation. • The properties of fire retardant and ageing resistance for EP/3% AST@Kaol were improved. • Fire retardancy and ageing resistance mechanism of EP/3% AST@Kaol was analyzed. [ABSTRACT FROM AUTHOR]

• A phosphaphenanthrene/benzimidazolone-containing flame retardant (POBDBI) was synthesized successfully. • POBDBI imparted excellent flame retardancy and smoke suppression to EP. • POBDBI exerted flame-retardant effect both in condensed phase and gaseous phase. A novel flame retardant POBDBI was generated by the reaction of p-dibenzaldehyde, 5-amino-2-benzimidazolinone and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and employed to epoxy resin. The structure of POBDBI was measured by FT-IR and NMR tests. Then flame-retardant EP was fabricated by using POBDBI as a flame-retardant. The thermal stability, flame-retardant performance and fire behavior were investigated by a serious of comprehensive instruments. Combustion tests show the flame-retardant performance of composite materials has been significantly improved. For example, the EP/POBDBI-1.0 with the phosphorus content of 1.0% accorded a V-0 rating and its limiting oxygen index (LOI) value increased to 36.5%. Besides, total smoke production (TSP), peak heat release rate (PHRR) and total heat release (THR) of EP/POBDBI-1.0 dropped significantly, and the corresponding values were decreased by 48.4%, 48.9% and 8.7%, respectively. At the same time, the composition, morphology of chars and gaseous products of POBDBI were studied by X-ray photoelectron spectroscopy (XPS), FT-IR, scanning electron microscope (SEM) and Py-GC/MS. These results presented that POBDBI could not only exerted free radical capture effect, but also enhanced the density of char residue. [ABSTRACT FROM AUTHOR]