Peak CO Production Research Articles

Facile strategy of preparing excellently thermal-insulating and fire-safe building materials based on an aromatic Schiff base dicarboxylic acid without additional flame retardants

Developing excellently fire-safe and thermal-insulating building materials is a critical subject in the building sector. In this work, a novel aromatic Schiff base dicarboxylic acid (FN) was synthesized through a facile strategy to prepare high-performance rigid polyurethane foam (RPUF) composites with excellent thermal insulation and fire safety performance. The uniform dispersion of FN in polyether polyol improved the cellular structure of RPUF composites, which was conducive to increasing the thermal insulation of RPUF composites. Therefore, incorporating only 10 wt% FN into RPUF composite (RPUF/10FN) possessed the lowest wall temperature (51.9 °C) and room temperature (38.8 °C) with the lowest temperature growth rate under the continuous thermal radiation of the heat source among all samples in the small chamber test. Moreover, FN remarkably reduced the peak heat release rate, peak smoke production rate, and peak CO production rate of RPUF/10FN by 41.9%, 58.0%, and 59.6% without additional flame retardants, respectively, compared with those of pure RPUF. In addition, FN endowed RPUF/FN composites with better fire resistance and structural integrity compared with pure RPUF in the building facade fire test and fire protection test. The increased fire safety of RPUF/FN composites is due to the barrier effect of the formation of a dense and continuous char layer and the dilution effect of nonflammable gas generated by the thermal degradation of FN. Furthermore, FN enhanced the water contact angle of RPUF/FN composites from 112.2° for pure RPUF to 120.8° for RPUF/10FN, indicating that FN also enhanced the hydrophobicity of RPUF/FN composites. Therefore, the as-designed RPUF composites containing FN possessed a broad application prospect in the building field.

A novel P, N doped organic-inorganic hierarchical core-shell nanostructures: Reducing the fire risk of epoxy resin

The wide application of epoxy resin (EP) causes a great potential fire risk to humans and the environment. To effectively reduce the fire risk of EP, we designed a novel P, N-doped organic-inorganic hierarchical core-shell nanostructure (BN@PEI@UiO-66@PPA). Encouragingly, with only 2 wt% of BN@PEI@UiO-66@PPA, the peak heat release rate (PHRR) and total heat release (THR) were reduced by 47.2 % and 47.9 %, respectively, compared with those of pure EP, indicating a considerable enhancement in flame retardancy. The peak smoke release rate (PSPR), total smoke production (TSP), peak CO production rate (PCOPR), and peak CO2 production rate (PCO2PR) were significantly reduced by 46.0 %, 52.7 %, 72.1 %, and 75.1 %, respectively, compared with those of pure EP, indicating a significant reduction in fire toxicity. In addition, the mass of the char residue of BN@PEI@UiO-66@PPA/EP increased by 185.3 %, and the graphitization degree and thermal stability of the char were significantly improved. The results indicate that the various components in BN@PEI@UiO-66@PPA were functionally different and cross-assisted to form dense P-N-C char with high graphitization and high thermal stability, which effectively improved the fire safety of EP. This work provides a new reference for the construction of multi-component hierarchical structures to optimize their application in the field of fire safety of polymer composites.

Solvent-free intumescent fire protection epoxy coatings with excellent smoke suppression, toxicity reduction, and durability enabled by a micro/nano-structured P/N/Si-containing flame retardant

The development of solvent-free intumescent fire protection epoxy (EP) coatings with excellent durability is an extremely important issue for the protection of storage tanks and structural steels in the coating industry. In this work, a micro/nano-structured phosphorus/nitrogen/silicon-containing flame retardant (APP@Si) was synthesized by silica nanoparticles-modified ammonium polyphosphate, which was utilized to prepare high-performance intumescent fire protection epoxy resin (EP) coatings via a solvent-free method. APP@Si enhanced fire protection, smoke suppression, toxicity reduction, mechanical properties, and durability of solvent-free EP coatings. APP@Si with a 10 wt% loading level endowed solvent-free EP coating (EP/10APP@Si) with a limiting oxygen index value of 32.4 % and a UL-94 V-0 rating. Meanwhile, APP@Si declined the peak heat release rate, smoke factor, and peak CO production rate values of EP/10APP@Si by 77.5 %, 92.6 %, and 56.4 %, respectively, compared with those of pure EP. Moreover, the maximum back temperature of EP/10APP@Si was as low as 126.4 °C under heating for 1200 s in the back temperature test, which was 221.5 °C lower than that of pure EP. The increase in fire protection of EP/APP@Si coating was mainly attributed to forming an intumescent and dense char layer with strong strength and high expansion degree during combustion. In addition, APP@Si enhanced the flexural strength and impact strength of EP/10APP@Si by 12.0 % and 24.6 % compared with those of EP/10APP. Moreover, APP@Si also increased the water contact angles of EP/APP@Si coatings from 87.9° for pure EP to 93.3° for EP/10APP@Si. And the weight change rate of EP/10APP@Si was the lowest among all coatings after immersing in the deionized water for 20 days. Therefore, this work presented a feasible strategy for fabricating multifunctional solvent-free intumescent fire protection epoxy coatings, which was expected to be applied in the coating industry.

Synergetic modification of graphitic carbon nitride by Zr-based metal-organic framework and tetraethoxysilane for improving fire performance in composite coatings

In this study, in an attempt to get an excellent flame retardant, herein, a new nanofiller (CNP@UiO-66@TEOS) with polyethyleneimine (PEI) as a crosslinker, Zr-based metal-organic framework (UiO-66) and tetraethoxysilane (TEOS) modified graphitic carbon nitride (CN) was synthesized. Different characterization tests confirmed the successful preparation of CNP@UiO-66@TEOS. Then, CNP@UiO-66@TEOS was doped into intumescent fire retardant (IFR) coating by solution blending method and the coating (CNP@UiO-66@TEOS/EP) was gained after curing. As expected, the CNP@UiO-66@TEOS significantly improved the fire performance of the IFR coating. The coating (CNP@UiO-66@TEOS/EP) with the addition of 2 wt% CNP@UiO-66@TEOS reduced the backside temperature by 102.9 °C over that of pure EP, proving enhanced flame retardancy. Meanwhile, CNP@UiO-66@TEOS/EP achieved the highest expansion height (21.5 mm) in the furnace experiment, contributing to a lower heat transfer ratio. In addition, the thermogravimetric analysis revealed an increase in residual char content to 31.84 wt%, which helped to resist external heat penetration. Cone calorimeter testing (CCT) showed that the peak heat release rate (PHRR), total heat release rate (THR), peak smoke production rate (PSPR), total smoke production (TSP), peak CO production rate (PCOPR), and peak CO2 production rate (PCO2PR) of CNP@UiO-66@TEOS/EP were reduced by 29 %, 19 %, 35 %, 37 %, 36 %, and 19 %, respectively, compared to pure EP, demonstrating the improved flame retardancy and smoke suppression properties. The results indicated that CN formed a thermal barrier at a high temperature and UiO-66 generated zirconium oxide (ZrO2) to catalyze the formation of residual char, thus producing a barrier effect. The TEOS on the UiO-66 surface further decomposed to form a silicon network to enhance the char layer strength of the composite. The synergistic outcome of CN, UiO-66, and TEOS offers potential avenues for the development of efficient IFR coating.

Biomimetic construction of hierarchical MXene@PDA@CoFeOx nanohybrids towards efficient fire-safe epoxy nanocomposites with enhanced thermal conductivity and mechanical properties

Developing high-performance MXene-based polymer nanocomposites through a biomimetic method has been a research hotspot. However, it is still an intractable challenge to achieve MXene-based polymer nanocomposites with efficient fire safety, excellent thermal conductivity, and enhanced mechanical properties. Here, inspired by the adhesion of mussels, the hierarchical MXene@PDA@CoFeOx nanohybrid was fabricated by a self-assembly strategy and then employed to prepare epoxy resin (EP) nanocomposites. It has been found that MXene@PDA@CoFeOx can display excellent dispersion and interfacial compatibility in EP matrix. Thermogravimetric analysis shows that only 2.0 wt% MXene@PDA@CoFeOx results in excellent thermal stability and char yield (31.29 wt%) of EP under a nitrogen atmosphere. Combustion tests show that the 2.0 wt% MXene@PDA@CoFeOx confers efficient fire safety to EP. Remarkably, the EP-2.0%MXene@PDA@CoFeOx can obtain an attractive UL-94 rating of V0. Meanwhile, the peak heat release rate (pHRR), smoke factor (SF), and peak CO production rate (pCO) of EP-2.0%MXene@PDA@CoFeOx are dramatically decreased by 33.38%, 55.41%, and 36.84% in comparison to those of virgin EP, respectively. The efficient fire safety of EP nanocomposites is mainly attributed to the barrier effect, dilution effect, and catalytic carbonization effect of hierarchical MXene@PDA@CoFeOx. Furthermore, the MXene@PDA@CoFeOx enables EP to boast enhanced thermal conductivity (improved by 69.14%), impact strength (improved by 13.38%), and flexural strength (improved by 17.60%). This work offers a feasible biomimetic method for fabricating hierarchical MXene@PDA@CoFeOx nanohybrids and preparing efficient fire-safe EP nanocomposites with excellent thermal conductivity and mechanical performance.

Aromatic P/N/Co-containing microsphere flame retardant for enhancing fire safety and mechanical properties of epoxy coating with lower curing temperature

Improving fire safety performance is one of the most important measures to expand the application field of epoxy resin (EP) coatings. In this work, a novel aromatic phosphorus/nitrogen/cobalt-containing microsphere flame retardant (FNP-Co) was synthesized via a solvothermal method and proposed for fabricating high-performance EP coatings. EP coatings containing FNP-Co exhibited not only remarkable fire safety performance but also enhanced mechanical properties and lower curing temperature. The differential scanning calorimetry (DSC) test demonstrated that FNP-Co endowed EP/FNP-Co coatings with lower curing temperatures compared with that of pure EP, which was conducive to the processing of EP coatings. Furthermore, with incorporating 4 wt% FNP-Co, the limiting oxygen index (LOI) of EP coating (EP/4FNP-Co) was increased to 30.2 %. And the peak heat release, peak smoke production, and peak CO production rate of EP/4FNP-Co were reduced by 19.85 %, 36.3 %, and 34.18 %, respectively, compared with those of pure EP. It has been found that FNP-Co promoted the formation of a honeycomb-like and compact char layer for EP/FNP-Co coatings during combustion, which could play a “labyrinth effect” and barrier effect to prohibit the heat and pyrolysis gas transfer. Moreover, the flexural strength and flexural modulus of EP/4FNP-Co were enhanced by 2.9 % and 32.5 % compared with those of pure EP. The unique microsphere structure and synergistic effect of ternary flame-retardant elements of FNP-Co were responsible for the desirable integrated properties of EP coatings. Therefore, this novel microsphere flame retardant can impart EP/FNP-Co coatings with a broad application in the coating field.

Novel phosphorus-free and core–shell structured ZIF-67 for simultaneously endowing epoxy resin with excellent fire safety, corrosion and UV resistance

Two novel and eco-friendly phosphorus-free ZIF-based core–shell nanomaterials were prepared and employed to enhance fire safety of epoxy resins (EPs), which interestingly possessed both anti-corrosion and UV resistance properties. ZIF-based nanomaterials were firstly constructed by growing zinc hydroxystannate (ZHS) on surface of zeolitic imidazolate framework-67 (ZIF-67) to generate core by a simple etching method (ZIF-67@ZHS), and the sol–gel technique was then used to form shells on the surfaces (ZIF-67@ZHS@TiO2 and ZIF-67@ZHS@SiO2). After incorporation of the prepared nanomaterials into the EP, the introduced TiO2 and SiO2 shells effectively weakened the negative impact on the EP matrix because of abundant metallic elements exposed by the ZIF-67@ZHS core. In particular, the EP composite sample (EP/5ZIF-67@ZHS@SiO2) with the addition of 5 wt% ZIF-67@ZHS@SiO2 showed a better cone calorimeter combustion test result with a 32.0 % reduction in peak heat release rate (PHRR) compared to pure EP. Additionally, the EP composites containing 5 wt% ZIF-67@ZHS@TiO2 and ZIF-67@ZHS@SiO2 demonstrated a significant reduction in the release of toxic gases, specifically the peak CO production (COP) decreased by 17.2 % and 34.5 % relative to pure EP, respectively. Besides, both EP/5ZIF-67@ZHS@TiO2 and EP/5ZIF-67@ZHS@SiO2 coatings showed an order of magnitude improvement in impedance modulus at 0.01 Hz compared to pure EP, with EP/5ZIF-67@ZHS@SiO2 exhibiting no significant decline over 15 days. In addition, all EP composites containing modified ZIF-67 showed a decrease in UV transmittance, especially the UV transmittance of EP/5ZIF-67@ZHS@TiO2 between 350 - 400 nm decreased to below 1.8 %. This preparation strategy exhibits prominent potentials in application as a multifunctional advanced epoxy composite.

Cu(Ⅱ) and Co(Ⅱ) complexes decorated ammonium polyphosphate as co-curing agents on improving fire safety and mechanical properties of epoxy-based building coatings

Epoxy resin (EP) is widely used as an organic coating in the field of building materials (such as steel and timber). However, it’s high flammability and smoke release in fires further hinder its application in construction. Here, Cu(II) and Co(II) complexes decorated ammonium polyphosphates (BAPP@Cu and BAPP@Co) were synthesized by a facile strategy of chemical surface modification and used as multifunctional additives to enhance various properties of epoxy coatings. It has been found that both BAPP@Cu and BAPP@Co as co-curing agents not only promote the curing reaction of EP but also enhance the interfacial compatibility between the filler and the epoxy matrix. In addition, both BAPP@Cu and BAPP@Co endow EP with enhanced mechanical performance and heat insulation compared to pristine ammonium polyphosphate (APP). More importantly, both BAPP@Cu and BAPP@Co impart excellent fire safety to EP coatings. The peak heat release rate (pHRR) and peak CO production rate (pCO) of EP-6 %BAPP@Cu are decreased by 35.6% and 46.2%, respectively, compared to virgin EP. Similarly, EP-6 %BAPP@Co exhibits high fire performance, with a 57.7% reduction in pHRR and a 62.9% reduction in pCO, respectively, in comparison to virgin EP. This work reports a new strategy for the chemical modification of APP by metal complexes and provides a new perspective for the application of building coating materials.

A novel ternary inorganic–organic hybrid flame retardant containing biomass and MOFs for high-performance rigid polyurethane foam

In this work, using biomass polydopamine (PDA) as an intermediate interface, ammonium polyphosphate (APP), PDA, and ZIF-67 were combined into a ternary inorganicorganic hybrid flame retardant (A@P-Z). Compared with the flame retardant system composed of a physical mixture of APP and ZIF-67, the hybrid flame retardant not only strengthened the mechanical properties of RPUF composites owing to its good compatibility but also emerged with low total heat release, low total smoke production, and low peak CO production rate in cone calorimetry tests. RPUF/A@P-Z passed the UL-94 V-0 rating, which presented high flame-retardant efficiency of inorganicorganic hybrid flame retardants and industrial application value of the composites. Due to the contribution of synergistic catalysis, the residual char of RPUF/A@P-Z showed high graphitization and high-quality char composition in a rich, rigid structure, which produced an outstanding charring effect and barrier effect. The hybrid flame retardant also produced an impressive flame inhibition effect in the gas phase, inhibiting the production of organic fragments and releasing phosphorus-containing and nitrogen-containing gaseous compounds with free radical quenching and diluting effects. This work provides a new and efficient way to prepare high-performance RPUF composites using inorganicorganic hybrid flame retardants.

Killing three birds with one stone: A novel regulate strategy for improving the fire safety of thermoplastic polyurethane

Flammable and highly toxic smokes are roadblocks for thermoplastic polyurethanes (TPU) in high-tech applications. Herein, we reported polydopamine (PDA) as a functional adjuvant for the synthesis of [email protected]@Cu nanohybrids with a “Killing three birds with one stone” strategy, modulating the morphology and dispersion of ZIF-8, providing excellent adhesion capability to enhance the complexation of copper (Cu) particles, and playing a flame retardant function. The [email protected]@Cu nanohybrids presented a homogeneous dispersion and built up robust interfacial interactions with TPU substrate. Further, TPU/[email protected]@Cu composites exhibited excellent thermal stability, flame resistance and toxic smoke inhibition performance, as evidenced by high char residuals, low peak heat release rate (59.2% reduction), low peak smoke production rate (54.3% reduction) and low peak CO production (40.7% reduction). Because of the physical barrier effect of stable char layer, dilution effect of non-combustible gas and free radical scavenging effect of catechol groups, TPU composites were endowed with an excellent fire safety. Notably, metal compounds formed by thermal degradation of [email protected]@Cu nanohybrids were able to undergo cyclic redox reaction with carbon monoxide, significantly decreased the release of toxic gas.

Fire-safe epoxy composite realized by MXenes based nanostructure with vertically arrayed MOFs derived from interfacial assembly strategy

In this contribution, Ni-based metal organic frameworks (Ni-MOF) nanosheets with high specific surface area are grown on transition metals carbides (MXenes, denoted as MX) surface via vertical alignment, gestating the flame retardant of MX@MOF-B. With the addition of 2.0 wt% MX@MOF-B, the peak heat release rate, peak smoke production rate, peak CO production rate, peak CO2 production rate are reduced by 42.5 %, 26.7 %, 37.8 %, 54.9 %, while the peak concentrations of C2H6, CH4, HCN, NO, N2O are impaired by 91.3 %, 94.3 %, 89.6 %, 90.3 %, 60.9 %, suggesting the enhanced fire safety. Meantime, the fire performance index is elevated by 83.0 % and fire growth index is reduced by 37.2 %, demonstrating the promoted fire safety. Of note, the using of MX@MOF-B induces the promotion of 787.1 % in char yield after combustion, which shows higher graphitized degree and thus enables better protection for basal matrix. Flame retardation contrast with previous works also manifests the strength of MX@MOF-B in hindering the heat release and toxicants emission. This work offers a new paradigm for forging fire-safe polymer composites with low toxicity.

Synergistic effects of zeolitic imidazolate frameworks (ZIFs) with different transition metals on intumescent flame-retarded polypropylene composites: A comparative study

The use of intumescent flame retardants (IFRs) is considered an environmentally friendly and cost-effective strategy to suppress potential fire hazards from synthetic polymers. However, some conventional IFRs are neither efficient in developing a thermally stable char layer nor reducing the release of toxic byproducts during polymer combustion. In this work, we aim to discuss the effects of zeolitic imidazolate frameworks (ZIFs) on synergistically improving the flame retardancy behaviors in polypropylene (PP) composites, including thermal degradation (evolved gas analysis), free radical reactions in the gaseous phase (in-situ chemiluminescent image analysis), and carbonaceous structure in the condensed phase (micro-morphology and composition analysis). It is found that the transition metals in ZIFs can catalytically accelerate the crosslinking reaction at a lower initial temperature and decrease the amount of hydrocarbon volatiles in the gaseous phase. Once ignited, the embedded ZIFs can firstly bridge adjacent phosphorus chains in the polymer matrix to expand crosslinking degrees and then they are anchored in the developed N-doped phospho-carbonaceous networks after pyrolysis. As a result, more compact char residue structures are observed in the condensed phase for ZIF-reinforced composites. For example, by replacing 2 wt% of IFR with ZIF-67, the peak heat release rate, peak smoke production rate, and peak CO production rate are reduced by 69%, 80%, and 72%, respectively, when compared to the conventional composite. These results indicate an excellent solution to resolve inherent fire hazards associated with IFRs in polymers and achieve necessary efficiency for industrial applications. It also provides a new strategy for determining flammability characteristics and combustion mechanisms of polymer composites using in-situ chemiluminescence analysis.

Hollow LDH cage covering with ultra-thin MXenes veil: Integrated micro-nano structure upon heat release suppression and toxic effluents elimination for polymer

The using of epoxy resin (EP) has been compromised by its high fire hazard. In this context, MXenes nanoflakes have been preferred as flame retardant, considering its merits in suppressing heat as well as toxic gases emission. Nevertheless, it is difficult to achieve the desired flame retardancy efficiency when the MXenes dosage is low. Thus far, the development of nanostructure based on MXenes with high flame retardant capacity has been seldom investigated. In this contribution, we have designed a strongly-coupled micro-nano structure based on hollow LDH covering with ultra-thin MXenes veil (MX@H-LDH) via assembly strategy. When loading 5.0 wt% MX@H-LDH, peak heat release rate, total heat release, peak CO production rate and total CO production can be reduced by 54.6%, 37.5%, 47.4%, 63.6%, accordingly. Meanwhile, the prominence of MX@H-LDH in inhibiting the release of heat is confirmed via the comparison with previous works. The curbed toxic CO, NO and HCN releases are also discerned in gases phase analysis. Moreover, it is satisfactory to find that the using of MX@H-LDH strengthens the mechanical capability, assigned to the mechanical interlocking action. Briefly, this work can be instructive for the design of novel MXenes-based nanostructure, mining its potentials in polymer composites with high performance.

Construction of polyphosphazene-functionalized Ti3C2TX with high efficient flame retardancy for epoxy and its synergetic mechanisms

As a promising flame retardant, Titanium carbide (Ti3C2TX) MXene has shown synergetic flame retardancy with various modifying agents, especially phosphorus/nitrogen-containing flame retardants. However, the synergetic flame-retardancy mechanism of Ti3C2TX and modifying agent are unclear due to the complexity of reactions during the combustion process. Herein, polyphosphazene-functionalized Ti3C2TX nanosheets (MXene-PZN) were prepared and then added to epoxy resin (EP) to prepare the EP/MXene-PZN composites. Subsequently, the mechanical properties and the flame-retardant performance and mechanism were systematically investigated. The results showed an improved interfacial interaction and excellent compatibility of MXene-PZN nanosheets in the EP matrix, resulting in the storage modulus and tensile strength of EP/MXene-PZN-2.0 being increased by 46.5% and 68.4% respectively, as 2 wt% MXene-PZN was added into the EP matrix. Moreover, the flame-retardant tests showed that the peak heat release rate and total heat release of EP/MXene-PZN-2.0 were reduced by 44.8% and 54.8%, respectively, compared with pure EP, while 49.4% and 41.9% decrease in the peak CO production rate and the peak CO2 production rate were also achieved. Finally, focusing on the main existing forms of MXene-PZN in the EP matrix during different combustion stages, the flame-retardant mechanism of MXene-PZN functioned both in the condensed phase and gaseous phase was established. Thus, this work demonstrates a facile yet promising strategy to design efficient synergetic flame retardants.

Strongly-coupled magnetic nanospheres@trimetallic LDH hooding with thin MXenes veil: Sandwiched ternary nanostructure towards forging fire-safe EP with low toxicity

Transition metals carbides/nitrides (MXenes) have been utilized as flame retardants for epoxy resin (EP) with inherently high fire hazard. However, when the dosage of MXenes is low, the corresponding flame retardant efficiency is hard to meet the demand. Up to now, MXenes-based nanostructure with high flame retardation effectiveness has been rarely investigated. Hence, we have employed the assembly strategy to acquire a sandwiched ternary nanostructure (MX-Fe@LDH), based on strongly-coupled magnetic nanospheres@trimetallic LDH hooding with thin MXenes veil, which has never been reported before. With only 3.0 wt% MX-Fe@LDH dosage, the peak heat release rate, peak CO production rate, peak CO2 production rate, total CO production are reduced by 51.3%, 70.2%, 49.4%, 74.1%. Comparison with reported works also indicates the high effectiveness of MX-Fe@LDH in flame retardation. The curbed emissions of toxic NO and HCN gases are uncovered via Thermogravimetric analysis-infrared spectrometry test. Postmortem analyses have indicated that using MX-Fe@LDH contributes to engender char with high graphitized degree, which acts as safeguard for basal matrix. Stemming from the rational design, there is a strong mechanical interlocking action between MX-Fe@LDH and EP chains, further prompting the mechanical capabilities. This work may motivate the design of MXenes-based nanostructure towards forging fire-safe polymer composites.

Synergistic action of expandable graphite on fire safety of a self‐intumescent flame retardant epoxy resin

AbstractPreviously, it was reported that epoxy resin (EP) filled with ammonium polyphosphate (APP) and copper (I) oxide (Cu2O) at a mass ratio of 8/2 (APP8‐Cu2O2) as a self‐intumescent system demonstrated promising fire retardancy. To further improve the flame retardant efficiency, the possibility of expandable graphite (EG) as an effective synergist for the self‐intumescent EP system was revealed by limiting oxygen index (LOI) test. The results showed that the incorporation of EG increased the LOI value of EP/APP8‐Cu2O2 obviously. The highest LOI value was obtained at the EG/APP8‐Cu2O2 mass ratio of 3/7, indicating the optimal synergistic effect being achieved. Furthermore, UL‐94 test results showed that the excellent synergistic effect resulted in the addition of 13 wt% EG/APP8‐Cu2O2 of 3/7 not only endowed EP a relatively high LOI value of 34.3%, but also made it pass UL‐94 V‐0 rating. Moreover, the main fire hazard parameters obtained from cone calorimeter tests, such as peak heat release rate, total smoke production, and peak CO production were reduced 40.3%, 30.3%, and 46.2%, respectively by the combination effect of EG/APP8‐Cu2O2 with mass ratio of 3/7, suggesting the excellent improvement in the fire safety of EP significantly. Finally, a possible action mode, which would be beneficial for developing other flame retardant polymers with high fire safety, was proposed.

Nanohybrid of Co3O4 Nanoparticles and Polyphosphazene-Decorated Ultra-Thin Boron Nitride Nanosheets for Simultaneous Enhancement in Fire Safety and Smoke Suppression of Thermoplastic Polyurethane.

Thermoplastic polyurethane (TPU) is widely used in daily life due to its characteristics of light weight, high impact strength, and compression resistance. However, TPU products are extremely flammable and will generate toxic fumes under fire attack, threatening human life and safety. In this article, a nanohybrid flame retardant was designed for the fire safety of TPU. Herein, Co3O4 was anchored on the surface of exfoliated ultra-thin boron nitride nanosheets (BNNO@Co3O4) via coprecipitation and subsequent calcination. Then, a polyphosphazene (PPZ) layer was coated onto BNNO@Co3O4 by high temperature polymerization to generate a nanohybrid flame retardant named BNNO@Co3O4@PPZ. The cone calorimeter results exhibited that the heat release and smoke production during TPU combustion were remarkably restrained after the incorporation of the nanohybrid flame retardant. Compared with pure TPU, the peak heat release rate (PHRR) decreased by 44.1%, the peak smoke production rate (PSPR) decreased by 51.2%, and the peak CO production rate (PCOPR) decreased by 72.5%. Based on the analysis of carbon residues after combustion, the significant improvement in fire resistance of TPU by BNNO@Co3O4@PPZ was attributed to the combination of quenching effect, catalytic carbonization effect, and barrier effect. In addition, the intrinsic mechanical properties of TPU were well maintained due to the existence of the PPZ organic layer.

Bioinspired, stable adhesive Ti3C2Tx MXene-based coatings towards fire warning, smoke suppression and VOCs removal smart wood

Wood is an essential material widely used in a broad variety of daily life and industry. The development of an ecofriendly and smart wood towards potential environmental hazards such as fire hazards and air pollution still remains a huge challenge. Here, we report a bioinspired, stable adhesive, multifunctional coating for scalable construction of smart wood based on Ti3C2TX MXene network intercalated with cellulose nanocrystals (CNC). Polydopamine (PDA) is introduced as an intermediate adhesive bridge that possesses hydrogen bonds, van der Waals forces, and mechanical interlocking interactions to facilitate stable bonds of the MXene-based fire warning coating on wood surface. By constructing an intercalated architecture, CNC can not only solve the re-stacking of MXene nanosheets, but also serve as a thermoswitch that keep insulative mediator at room temperature, and promote the transport of electron triggered at higher temperature or on fires. During combustion, the MXene-based coating provides a denser, expanded physical barrier, captures the free radicals, and ultimately prevents the escape of smoke. Therefore, the optimized CNC/MXene coating exhibits high adhesion, sensitive fire response time (∼2.1 s), superior flame retardancy (LOI of 47.4 %, UL-94 V0 rate, and average heat release rate of 54.70 kW/m2), and excellent smoke suppression (total smoke rate of 119.9 m2/m2, peak CO2 production of 0.251 g/s, and peak CO production of 0.0037 g/s). In addition, smart wood has the potential photocatalysis oxidation capacity for volatile organic compounds (VOCs) removal (formaldehyde gas, 51 % removal rate within 60 min). This work puts forward a prospective strategy to fulfill multifunctional and high-performance coatings that simultaneously enhance the overall performance of wood, thus significantly contributing to expand its practical applications.

Synergistic effects of Al/Si double oxide on flame-retardant and smoke-suppressant wooden materials

Wooden materials have many advantages, but they easily burn and release CO, CO2, and harmful volatile organic compounds (VOCs), which pose threats to health and safety. This work adopted a low-cost method, using environmentally friendly silicate (Na2SiO3), aluminum sulfate (Al2(SO4)3), and water-borne epoxy resin to prepare composite poplar wood (Al–Si-EPW), which synergistic displayed flame retardancy, smoke suppression, and self-extinguishing characteristics. The time of peak heat release rate (HRR) and peak smoke production rate (SPR) of Al–Si-EPWwere 340 s and 315 s, which were delayed by about 105 s and 100 s compared with untreated wood (UW), respectively. This provides more security for controlling the fire spread and evacuating people. The peak value of heat release rate and smoke production of Al–Si-EPW decreased by 39.04% and 34.68%, and the peak CO2 production (CO2P) and CO production (COP) were reduced by 69.75% and 74.74%. Moreover, the main category and the amount of VOCs released during the combustion process decreased significantly. With the increase in aluminum sulfate dosage, it showed better flame retardant and smoke suppression effects. This indicated that Al–Si-EPW only released a small amount of toxic smoke, greatly reducing the possibility of suffocation and damage. Therefore, this material can be widely used as a flame-retardant wood building material.

Interfacially-engineered PBA based hierarchical structure with Ni(OH)2 nanocatalyst towards fire retardation of epoxy resin

The extended usage of epoxy resin (EP) has suffered from the notorious issue of high fire hazard, including the release of considerable heat and emission of abundant toxicants (smoke and toxic gasses). Hence, a prussian blue analogue (PBA) based hierarchical structure (Co@Ni(OH)2-A) with Ni(OH)2 nanocatalyst, is proposed via interfacial-engineering strategy, towards reducing the fire hazard of EP. As revealed, Co@Ni(OH)2-A shows strong interfacial catalytic strengths both in charring of decomposed volatiles and oxidizing of toxic gasses. By using 4.0 wt% Co@Ni(OH)2-A, the peak heat release rate, peak smoke production rate, total smoke production and peak CO production rate are reduced by 45.5%, 55.0%, 44.3% and 65.3%, respectively. Fire resistance comparison with previous works confirms the advantage of Co@Ni(OH)2-A in toxicants elimination. Owing to the well-generated hierarchical structure-polymer interfaces, the greatly enhanced mechanical property is obtained. Generally speaking, Co@Ni(OH)2-A holds exceptional efficacy in promoting the polymer fire safety and mechanical performance. This investigation may offer useful enlightenments for acquiring high-performance EP composites via designing PBA based flame retardants with hierarchically tailored structure.