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• 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]

• The strength of chars was heightened significantly by the bi-component flame retardant (PODSE/APP). • 20 wt% PODSE/APP led to an 88.1 % and 87.0 % reduction in pSPR and TSP. • The char residue was substantially increased by 89.2 % with 20 wt% PODSE/APP. • PODSE/APP changed the internal structure of chars into honeycomb with higher expanded ratio. The intrinsic flammability and high smoke production are two major defects that epoxy resin (EP) must overcome during the practical application. However, few current studies have acknowledged in both fire resistance and smoke suppression performance, which is vitally interrelated with quality of char layers. Herein, a P/S-containing compounds (PODSE) was prepared via esterification and then supplemented with ammonium polyphosphate (APP) to develop an intumescent flame retardant for heightening the strength of char. With 20 wt% PODSE/APP, the peak of smoke produce rate (pSPR) and total smoke production (TSP) of EP3 reduced by 88.1 % and 87.0 %, respectively, indicative of superior smoke suppression performance. It attained a limited oxygen index (LOI) value of 40.0 % with V-0 rating during vertical burning test (UL-94) and the char residues at 700 °C increased from 15.8 % to 29.9 % compared with pure EP. More importantly, in order to figure out the reason for such highly-improved performance, the residual chars after cone calorimeter (CC) test were comprehensively investigated. The result showed that the internal chars of the samples modified by PODSE/APP exhibited honeycomb-like structure instead of irregular network structure of the one modified with single PODSE, endowing the char layers with higher expanded ratio and strength, which responded to excellent insulation effect. This finding provided theoretical and experimental basis for further exploration of P/S synergistic intumescent flame retardant. [ABSTRACT FROM AUTHOR]

With the specialization and diversification of the use environment of composite products, composite materials should have good comprehensive properties. Abiding by this target, we successfully prepared a transparent epoxy resin (EP) composite with flame retardancy, low smoke, enhanced toughness, high glass transition temperature by blending the flame-retardant POI synthesized in this work. POI was synthesized from phosphophenanthrene, vanillin and histidine, and the combination of these three raw meticulously selected endowed POI molecule with excellent versatility. EP composite modified with 10 wt% POI (EP/POI-10) obtained a limiting oxygen index (LOI) of 30.5% and received the V-0 grade (UL-94). The reduction of total smoke production by 78.1% via cone calorimeter tests was obtained. The impact strength of EP/POI-7 increased by 48.2% due to the energy dissipation of cracks from POI. The comprehensive analysis of the dual-phase revealed that the improvement of flame retardance was attributed to the joint action of the gaseous phosphorus free radicals quenching and the protecting of condensed coke. Moreover, EP/POI obtained high glass transition temperature as well as good transparency. [Display omitted] • A bio-based flame retardant molecule POI was synthesized. • High-performance composites of EP/POI with high T g , toughened and transparent were prepared. • The EP/POI showed a remarkable smoke suppression effect with a 78.1% reduction in TSP. [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]