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• Novel phosphine oxide-containing bio-based anhydride was synthesized and used as epoxy curing hardener. • Flame-retardant epoxy vitrimer contains carboxylic ester network. • The EV exhibits excellent flame retardancy attributed to both gas and condense-phase actions. • Carboxylic ester dynamic bonds impart excellent reparability and reprocessability. • The EV exhibits excellent mechanical performance before and after recycling. The conception of epoxy thermosets with both reprocessability and flame retardancy delineates a new horizon in polymer science, offering a material solution that is not only superior in fire safety but is also environment friendly. Herein, a flame-retardant epoxy vitrimer (EV) was prepared using partially bio-based IADPPO (diphenylphosphine oxide itaconic anhydride) and citric acid as curing reagents via a solvent-free process. Their incorporation created covalent adaptable networks (CANs) in the matrix which promote reprocessability and recyclability. The EV exhibits excellent thermal stability with high initial decomposition temperature (T - 5wt% ∼308 °C) and high glass transition temperature (T g ∼107 °C), similar to the blank EV (115 °C). The flame retardancy, mechanical properties, transesterification-based reprocessability, and flame-retardant mechanism were investigated. The EV containing 3 wt% phosphorus (EV IADPPO 3P) achieved UL-94 V0 classification with a limiting oxygen index (LOI) of 27%, while the virgin sample Blank EV (without phosphorus) burned completely. Additionally, increased flexural strength of 79% was observed for EV IADPPO 3P compared to Blank EV. Furthermore, the flame-retardant EV showed high malleability and reparability that could be thermomechanically reprocessed without sacrificing the thermal, mechanical, and flame-retardant properties. Thus, the newly developed epoxy vitrimer is not only fire-safe but fulfills the sustainability goals of today's society. [Display omitted] [ABSTRACT FROM AUTHOR]

• Vitrimer has higher thermal stability but lower fire performance than epoxy. • Melting above vitrimer transition temperature affects LOI and UL-94 results. • From 2% phosphorus content, rapid charring prevents the melting of vitrimers. • The same flame retardants perform better in vitrimers than in PER epoxy. • Imine type vitrimers leverage the phosphorus-nitrogen synergism. We developed flame retarded polyimine type vitrimers and carbon fibre reinforced composites using two additive and a reactive flame retardant containing phosphorus: ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP); and N,N',N "-tris(2-aminoethyl)-phosphoric acid triamide (TEDAP). We characterised the vitrimer matrix materials by differential scanning calorimetry (DSC), thermal analysis (TGA), limiting oxygen index (LOI), UL-94 test and mass loss calorimetry (MLC), while the vitrimer composites by LOI, UL-94 test, MLC and dynamic mechanical analysis (DMA). We compared the performance of the vitrimer systems to a benchmark pentaerythritol-based aliphatic epoxy resin system (PER). The vitrimer reference had higher thermal stability but lower fire performance than the PER aliphatic reference epoxy. At lower phosphorus content, the vitrimer systems exhibited a melting above their vitrimer transition temperature, which negatively affected their LOI and UL-94 results. From 2% phosphorus content, rapid charring and extinguishing of vitrimers prevented the softening and deforming. The superior performance of these same flame retardants in vitrimer systems could be attributed to the high nitrogen content of imine-based vitrimers in combination with phosphorus flame retardants, exploiting nitrogen-phosphorus synergism. In both matrices, flame retardants with solid phase action lead to better fire performance, while in composites, the lowest peak heat release rates (152 kW/m2 in vitrimer composite) were achieved with RDP acting predominantly in the gas phase, as carbon fibres hindered the intumescent phenomenon. [Display omitted] [ABSTRACT FROM AUTHOR]

• P-containing 1-vinylimidazole salts are used as crosslinking agents for VERs. • P-containing groups are introduced into the resin via ionic bonds. • Influence of the oxidation state of P on the flame retardancy of VERs is studied. Different reactive flame retardants have been extensively developed for vinyl ester resins (VERs), but very few of them can yield a flame-retardant resin that meets defined standards (e.g. UL-94 V-0 rating). In this work, phosphorous-containing 1-vinylimidazole salts (called VIDHP and VIDPP) were synthesized through the facile neutralization of the acid and 1-vinylimidazole. VIDHP and VIDPP were then applied as flame-retardant crosslinking agents of VERs, by which phosphorus-containing groups could be incorporated into the resin chain via ionic bonds. VIDHP/VER and VIDPP/VER showed a high curing activity and can be well cured in moderate temperatures. With 20 wt.% additions of VIDHP and VIDPP, VIDHP20/VER, and VIDPP20/VER presented a limiting oxygen index value of 29.7 % and 28.4 %, respectively, with the latter achieving a UL 94 V0 rating. In the cone calorimetric test, compared to the unmodified VERs, VIDPP20/VER exhibited large reductions in the peak heat release rate, total heat release rate, and total smoke release rate while VIDHP20/VER demonstrated comparatively inferior performance in terms of the heat release. VIDHP20/VER and VIDPP20/VER showed good thermal stability and presented a little lower glass transition temperature than the control sample. VIDPP with a low phosphorus oxidation state (+1) demonstrated high flame-retardant activities in the gaseous phase, whereas VIDHP with a high phosphorus oxidation state (+5) primarily exhibited efficacy in the condensed phase. [ABSTRACT FROM AUTHOR]

• The Layer-by-Layer is used to coat keratin fibers from the tannery wastes. • Chitosan and cellulose nanofibrils are employed as coating constituents. • The coated fibers are used to produce lightweight fiber networks. • The produced lightweight materials show excellent flame retardant properties. The increasing consciousness about the depletion of natural resources and the sustainability agenda are the major driving forces to try to reuse and recycle organic materials such as agri-food and industrial wastes. In this context, keratin fibers, as a waste from the tannery industry, represent a great opportunity for the development of green functional materials. In this paper, keratin fibers were surface functionalized using the Layer-by-Layer (LbL) deposition technique and then freeze-dried in order to obtain a lightweight, fire-resistant, and sustainable material. The LbL coating, made with chitosan and carboxymethylated cellulose nanofibers, is fundamental in enabling the formation of a self-sustained structure after freeze-drying. The prepared porous fiber networks (density 100 kg m–3) display a keratin fiber content greater than 95 wt% and can easily self-extinguish the flame during a flammability test in a vertical configuration. In addition, during forced combustion tests (50 kW m–2) the samples exhibited a reduction of 37 % in heat release rate and a reduction of 75 % in smoke production if compared with a commercial polyurethane foam. The results obtained represent an excellent opportunity for the development of fire-safe sustainable materials based on fiber wastes. [Display omitted] [ABSTRACT FROM AUTHOR]

• The highly flexible composite paper has good mechanical properties and can withstand more than 10,000 times its own weight. • The flexible composite paper exhibits exceptional flame-retardant properties along with controlled, high-efficiency, and stable Joule heating performance. At a low voltage of 2.0 V, the surface temperature reaches 156.8 °C within 10 s and remains stable over a period of 1800s. • The flexible composite paper-based TENG can power commercial computers, delivering an output voltage of 55.6 V under a working environment of 2 Hz and 7 N. When the external load is 10 MΩ, its maximum output power reaches 15.6 µW. In recent years, polymer-based triboelectric nanogenerators (TENGs) have been increasingly applied in the field of flexible wearable electronics. However, the lack of flame retardancy of existing TENGs greatly limits their applications in extreme circumstances. Herein, an ultra-thin and highly flexible aramid nanofiber (ANF)/MXene(Ti 3 C 2 T x)/Ni nanochain composite paper was prepared through vacuum-assisted filtration and freeze-drying technology. Owing to the synergistic effect between ANF and MXene, the composite paper not only possessed excellent mechanical properties, which were able to withstand over 10,000 times its own weight, but also exhibited outstanding flame-retardant and controllable Joule heating capabilities. Moreover, the mechanical energy capture characteristics of the composite paper-based TENG were evaluated, resulting in the open-circuit voltage (55.6 V), short-circuit current (0.62 μA), and transferred charge quantity (25 µC). It also could enable self-powering as a wearable electronic device with an instantaneous power of 15.6 μW at the optimal external resistance of 10 MΩ. This work is intended to set TENG as safe energy harvesting devices for reducing fire hazards, and will provide a new strategy to broaden the application ranges of TENG. [Display omitted] [ABSTRACT FROM AUTHOR]

• Nanosilica (nSiO2) from rice husk was successfully synthesized and characterized. • PU foam/nSiO2/flame retardant additives nanocomposites were successfully synthesized. • Thermal stability and fire resistance of nanocomposite were significantly improved. • Microstructure, thermal conductivity and mechanical properties were deeply analyzed. This study focuses on the improvement of the thermal stability and flame-retardant performance of polyurethane (PU) foam by using effective flame-retardant additives and nano silica (nSiO 2) particles from rice husk. The addition of non-halogen flame retardants (FRs) including aluminum trihydroxide (ATH), triphenyl phosphate (TPP), and diammonium phosphate (DAP) leads to markedly enhanced thermal stability and fire resistance of the PU/nSiO 2 /FRs nanocomposites, resulting in achieving UL-94 HB standard. In particular, the nanocomposites met the UL-94 V-0 criteria thanks to the inclusion of DAP at 25 phr. The LOI value of the nanocomposites reached 26 % which is much higher than that of PU/nSiO 2 nanocomposite, about 20 %. In order to further understand the fire-proof mechanism, the residue char layer remaining of the PU/nSiO 2 /FRs nanocomposites after being burned was also investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). In addition, the microstructure, thermal stability, thermal conductivity, and mechanical properties of nanocomposites were also evaluated in this study. [ABSTRACT FROM AUTHOR]

• Environmental organic-inorganic coatings based on chitosan for flame-retardant FPUF have been prepared. • PCS/GP@FPUF with 35 wt% reaches the UL-94 V-0 rating and presented 32 % decrease of PHRR and 22% reduction of EHC. • PCS/GP has not damaged the compressive properties of FPUFs. • PCS/GP@FPUF shows excellent antibacterial properties against E.coli and S.aureus. In this work, the coatings used phosphorylated chitosan (PCS) and GP-108 via the dip-coating method presented exceptional flame retardancy and antibacterial properties for flexible polyurethane foams (FPUF). PCS/GP@FPUF with 35% weight gain of PCS/GP can receive the UL-94 V-0 rating and obtain a 32% reduction of peak heat release rate value compared with that of FPUF, and it remains relatively dense char residues. The effective heat of combustion of PCS/GP@FPUF is 21.6 kJ/g, presenting a 22% decrease compared with that of FPUF. Meanwhile, the PCS/GP coatings mainly have the condensed-phase flame-retardant mechanism associated with the analysis of char residues and the volatile products released through the thermal degradation process. X-ray photoelectron spectroscopy results confirm that the char residues of PCS/GP@FPUF consist of highly-graphitized carbon and it formed P-N-Si synergistic char layers. In addition, the antibacterial rates of PCS/GP@FPUF against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are 99.99%, and the incorporation of GP-108 does not influence the antibacterial properties of PCS. Importantly, the resiliency of FPUFs has been slightly influenced. Briefly, the flame-retardant and antibacterial FPUFs with wonderful resiliency are hopeful to be applied as filler materials for vehicle seats and obtain longer service lives. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel series of bio-based, lignin flame retardants (DAL- x) are synthesized. • DAL- x endows epoxy resin with desired flame retardancy and smoke suppression. • DAL- x improves the thermal stability and mechanical properties of epoxy resin. • DAL- x acts in both gas and condensed phases during combustion. Fabricating a high-performing thermoset using bio-based flame retardant is critical for the sustainable development of engineering materials with superior fire safety and robust mechanical properties. Herein, the epoxy (EP) composites with the industrial requirements are manufactured with a novel high-efficient, lignin-based flame retardant named DAL- x , which is fabricated by grafting 9, 10-dihydro-9-oxa-10-phosphaze-10-oxide (DOPO) onto lignin. The resulting DAL- x /EP composite exhibits excellent flame retardancy with a desirable UL-94 V-0 rating and a satisfactory limiting oxygen index (LOI) of 29.8% due to the appropriate phosphorus content of DAL- x with adjustable molecular chain structure. Moreover, the DAL- x /EP composite shows an unexpected improvement in the elastic modulus (∼36%) and well-preserved strength and ductility compared with those of pure EP. This work offers a feasible strategy for creating efficient bio-based flame retardants utilizing industrial waste lignin and preparing high-performance EP composites that meet the demanding requirement of fire retardancy in industries, contributing to the circular economy and sustainability. [Display omitted] [ABSTRACT FROM AUTHOR]

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• Multifunctional cotton fabric has been prepared via a layer-by-layer method. • Cotton-10BL-Si shows superhydrophobic and self-extinguishing behaviors. • Cotton-10BL-Si has great potential in EMI shielding and motion sensors. • Cotton-10BL-Si shows satisfying washability and durability. Multifunctional intelligent fire-safe cotton fabric promises next-generation fire-fighting uniform and sensor applications. However, cotton fabrics' hygroscopicity and intrinsic flammability significantly impede their potential applications in industries. Herein, we report a superhydrophobic fireproof cotton fabric (PEI-APP-PEI-MXene) generated via sequential layer-by-layer deposition of polyethyleneimine (PEI), ammonium polyphosphate (APP), and titanium carbide (MXene), followed by hydrophobic treatment with silicone elastomer. Compared to untreated cotton, the treated cotton fabric with 10 polymolecular layers exhibits ∼43% and ∼42% reductions in the peak heat release rate and total heat release, respectively, a desired UL-94 V-0 rating, and a high limiting oxygen index (LOI) value of 39.5 vol.%. In addition to that, the treated fabrics displayed improved electromagnetic interference (EMI) shielding and motion-sensing abilities. The presented work provides a facile and effective surface modification approach to generate multifunctional cotton fabrics with promising practical applications. [ABSTRACT FROM AUTHOR]

• A black phosphorus-MXene@polydopamine nanohybrid was synthesized. • The TPU/BP-MXene@PDA nanocomposite simultaneously showed reinforcing and toughening effects towards TPU. • The TPU/BP-MXene@PDA nanocomposite could be achieved excellent thermal stability, mechanical properties and flame retardancy. • A synergistic flame-retardant mechanism between black phosphorus and MXene in the TPU were discussed and clarified. Black phosphorus (BP), as one of the most promising fillers for flame retarding polymer, has been seriously limited in practical application, due to the agglomeration and poor structural stability challenges. Here, the BP was modified by MXene and polydopamine (PDA) via ultrasonication and dopamine modification strategy to improve the structural stability and dispersibility in the matrix. Then, the obtained (BP-MXene@PDA) nanohybrid was employed to promote the mechanical performance, thermal stability, and flame retardancy of thermoplastic polyurethane elastomer (TPU). The resultant TPU composite containing 2 wt.% of BP1-MXene2@PDA showed a 19.2% improvement in the tensile strength and a 13.8% increase in the elongation at break compared to those of the pure TPU. The thermogravimetric analysis suggested that BP-MXene@PDA clearly enhances the thermal stability of TPU composites. Furthermore, the introduction of the BP-MXene@PDA nanohybrids could considerably improve the flame retardancy of TPU composite, i.e., 64.2% and 27.3% decrease in peak heat release rate and total heat release, respectively. The flame-retardant mechanisms of TPU/BP-MXene@PDA in the gas phase and condensed phase were investigated systematically. This work provides a novel strategy to simultaneously enhance the fire safety and mechanical properties of TPU, thus expanding its industrial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Currently, there is an imperative demand for developing a novel flexible heater with high adhesion, breathability, and extreme condition resistance, such as ultra-high temperatures and even fire. Herein, a high-adhesion, flame-retardancy, and anti-bacteria copper nanoparticles networks/nylon 6 woven fabric (CNNs/NWF) wearable heater with a "sandwich-like" structure has been designed and fabricated based on phatic acid/aminopropyltriethoxysilane (PA/APTES) hybrid coating. On the one hand, the CNNs/NWF wearable heater exhibited superb electrothermal behavior working at a peak temperature of 208.8 °C powered with 2.0 V, better than that of wearable heaters in the recently reported literature. On the other hand, the vertical burning test showed that the heater possesses splendid flame retardancy. Furthermore, the PA/APTES coating could deposit a nanoscale porous protective film on the surface of CNNs/NWF, which imparts the heater with relatively excellent oxidation resistance and breathability. In addition, the antibacterial efficiency against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) still reached 100% after 50 times of standard washing and being electrified at 2.0 V for 5 min, keeping humans away from the threat of bacterial infections. We think that the heater in this research could be extended to wearable heating devices. [ABSTRACT FROM AUTHOR]

• This review reports the state-of-the-art design of flame-retardant RPUF. • The reactive, additive and coating type flame retardants for RPUF are discussed. • The flame-retardant and thermal conductive properties of RPUF are compared. • Key challenges and opportunities for future flame-retardant RPUF are described. Driven by global environmental concerns, many efforts have been made to develop halogen-free flame retardants for rigid polyurethane foam (RPUF). These environmentally benign flame retardants are mainly divided into (i) reactive, (ii) additive, and (iii) coating types. The last decade has witnessed great progress of these three strategies, which enhance the fire safety of RPUF and maintain even improve the thermal insulation properties. This comprehensive review focuses on the up-to-date design of the reactive, additive, and coating flame retardants, and their effects on flame retardancy and thermal conductivity of RPUF. Moreover, the practical applications of the as-prepared flame-retardant RPUFs are highlighted. Finally, key challenges associated with these three kinds of flame retardants are discussed and future research opportunities are also proposed. [ABSTRACT FROM AUTHOR]

• MXene/PP composites are prepared by hot-pressing PP non-woven fabric coated with functionalized MXene. • The final composite exhibits an EMI shielding performance of ∼90 dB (8–12 GHz, thickness ∼400 μm). • The resultant MXene/PP composites are mechanically robust with a superior anti-fatigue capability. • The resultant MXene/PP composites exhibit a self-extinguishing capability. Flame-retardant composites with high electromagnetic interference (EMI) shielding performance are desirable for electronic device packaging. Despite great potential of MXene for high EMI, it still remains a great challenge to develop high-performance flame-retardant polymer/MXene composites with excellent EMI shielding effectiveness because of the poor oxidative stability of MXene. Herein, phosphorylated MXene/polypropylene (PP) composites are prepared by coating phosphorylated MXene on PP fabric followed by spraying polyethylenimine (PEI) and hot-pressing. The phosphorylated MXene proves to be more durable against oxidation than pure MXene due to the protection effect of polyphosphates. Upon hot-pressing, melted PP fibers are fused together at their contact points and thus as-prepared composites are bi-continuous with two interpenetrating phases. The composites show significantly improved thermal stability and flame retardancy relative to pure PP, with a low total heat release (THR) of 3.7 kJ/g and a heat release rate (HRR) of 50.0 W/g, which are reduced by 78% and 87%, respectively. In addition, the composites exhibit a high electrical conductivity of ∼36,700 S/m and an EMI shielding performance of ∼90 dB over the whole frequency range of 8–12 GHz with a thickness of ∼400 μm. The as-developed PP/MXene composites hold great promise for reliable protection of next-generation electronic devices working in complex environments. [ABSTRACT FROM AUTHOR]

• New synthesis of carbon dots (CDs) with high quantum yield of 86% is demonstrated. • Integration of CDs and polymers forms highly fluorescent supraballs and patterns. • CDs show superior flame retardancy for highly flammable polymeric foams and fibers. • Molecular dynamics simulation is conducted for flame retardancy behavior of CDs. Facile strategy enabling the fabrication of carbon dots (CDs) with favorable performance useful for various applications is highly desirable. Here, we report the fabrication of highly fluorescent carbon dots (CDs) towards sensitive metal ion detection, brightly fluorescent printing pattern, as well as green flame retardants for synthetic polymeric materials. CDs are synthesized by solvothermal treatment of polypropylene carbonate (PPC) with ethylenediamine, and the quantum yield of CDs could increase from 30% to 86% by further adding trace of citric acid. The abundant functional groups on the surface of CDs allow CDs well incorporated into polymers to form CD-loaded polystyrene (PS) microspheres, which are employed to construct fluorescent supraballs via triphase microfluidic technique and used as "inks" for uniform fluorescent patterns. Interestingly, the resultant CDs show good flame retardancy for highly flammable polymeric foams and fibers. The CDs surpass previously reported flame-retardant additives, to show excellent combustion resistance that the addition of 20 wt% CDs causes 75% decrease in the peak of heat release rate (P-HRR) for polyurethane (PU) foams. Significantly, a molecular dynamics simulation process for PU/CDs combustion is constructed. This work may spur the preparation and application of high-performance carbon-based nanomaterials. [Display omitted] [ABSTRACT FROM AUTHOR]

• POSS modified HNTs were synthesized successfully by using a silane agent as a chemical bridge. • The POSS in combination with HNTs endows TPU with excellent flame retardancy without scarifying the mechanical property. • The incorporation of 2 wt% HNTs-POSS into TPU could effectively reduce the peak of the peak of CO production rate and total smoke release during combustion. Halloysite nanotubes (HNTs) have been considered as a promising flame retardant fillers for polymers. In this work, the polyhedral oligomericsilsesquioxane (POSS) containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical bridge. The POSS modified HNTs (HNTs-POSS) dispersed uniformly in the thermoplastic polyurethane (TPU) matrix and endowed TPU nanocomposites with enhanced tensile properties and fire safety. Cone calorimeter tests revealed that the introduction of 2 wt% HNTs-POSS to TPU matrix remarkably reduced the peak of heat release rate (PHRR) and total heat release (THR) by 60.0% and 18.3%, respectively. In addition, the peak CO production rate and total smoke release (TSR) could be significantly suppressed by the addition of HNTs-POSS. The well dispersed HNTs in combination with the ceramified silicon network from the thermal decomposition of POSS contributed to the formation of a continuous and compact char layer, exhibiting a tortuous effect by inhibiting heat diffusion and evaporation of volatile gaseous. In addition, the released crystal water from HNTs could dilute the combustible volatiles and then decline the combustion intensity. The tensile tests demonstrated that introduction of 2 wt% HNTs-POSS would enhance the maximum stress of TPU nanocomposite with a slight decrease of elongation at break. The combination of HNTs and POSS through the construction of effective interfacial interactions provides a feasible way to effectively enhance the fire safety of TPU nanocomposites without scarifying ductility. [ABSTRACT FROM AUTHOR]

The article presents information on a paper related to the development of nanocomposites in the last decade and their use in the fire reduction mechanism. It informs that the mechanism of improved flame retardancy can now be linked to the enhanced char formation. It further informs that the dispersion of suitable fillers to a nanometer level within a polymer matrix is necessary for the formation of nanocomposites.

The effects of different organophosphorus and brominated-compound based flame-retardant (FR) commercial finishing agents on the functional properties and thermal behaviour of cotton, polyester, viscose and P/V blends were studies. It was observed that organophosphorus-based FR finishing agents enhanced flame retardancy in polyester by enhancing the melt-dripping phenomenon and, in the case of cellulose, enhanced flame retardancy through the formation of char. All finishes were found durable up to five commercial washings. However, drastic reduction in tensile strength (up to 50%) in the case of cotton was observed after finishing treatment. After the FR treatment, bending length and drape % of the fabric increased. About 15-20% loss in air-permeability value was observed. [ABSTRACT FROM AUTHOR]