Flame Retardant Coatings Research Articles

Small-scale experimental study on EPS ETICS and flame-retardant coating reaction-to-fire performance

External thermal insulation composite systems (ETICS) are a common and energy-efficient cladding system. Thermoplastic expanded polystyrene (EPS) is widely used as an insulation core. However, such combustible material has aggravated fire incidents in recent years, thus it is essential to improve its fire behavior. To evaluate the performance of EPS ETICS, a series of specimens with different flame-retardant (FR) coatings were tested using a small-scale bench and a mass loss calorimeter with a maximum heat flux of 40 kW/m2. When untreated EPS ETICS are exposed to heat, the EPS foam degrades, releases a large volume of combustible gases, and ignites. Applying FR agents such as FR surface paint and expandable graphite blended coating can stop flame propagation, reduce total heat release by approximately 50%, and preserve about 50% of the EPS foam during heat exposure. This enhances significantly the fire safety of EPS ETICS.

Investigating Intumescent Flame-Retardant Additives in Polyurethane Foam to Improve the Flame Resistance and Sustainability of Aircraft Cabin Materials

Polyurethane (PU) foam has a high flammability and is widely used in aircraft interiors, presenting a significant danger to occupants. This study analysed three composite intumescent flame-retardant (IFR) coatings for flexible PU foam; expandable graphite (EG), ammonium polyphosphate (APP) and alginate (AG). The coatings were prepared in concentrations of 5 wt%, 10 wt%, and 50 wt% with an acrylic binder. The coated samples were characterised using cone calorimetry, SEM, and mechanical testing. The findings showed peak heat release rate, total heat release, and carbon dioxide production from the 10 wt% triple-layer coating (EG:APP:AG) was 52%, 32%, and 58% less than the PU control. The char of the 10 wt% triple-layer sample effectively suppressed smoke release and inhibited the transfer of fuel and gas volatiles. Mechanical testing demonstrated a 3.4 times increase in tensile strength and a 15.4 times increase in compressive strength (50% compression) compared to the control PU with the 10 wt% triple-layer coating. A fire dynamics simulator model was developed that demonstrated large-scale flammability modelling for commercial aircraft. Future work can explore the integration of IFR coatings into computational analysis. These new bio-based coatings produced promising results for aircraft fire safety and flammability performance for PU polymers.

Development of sustainable flame-retardant bio-based hydrogel composites from hemp/wool nonwovens with chitosan-banana sap hydrogel

Flame retardant (FR) finishing is crucial for developing protective textiles, traditionally relying on halogen, phosphorus, and phosphorus-nitrogen chemistries, which have limitations like toxicity and fabric stiffening. Innovative approaches such as nanotechnology, plasma treatments, and natural resource-based finishes are being explored to achieve sustainable FR textiles. This study presents the development and comprehensive characterization of hydrogel composites made from nonwoven fabrics composed of various hemp/wool blends (70/30, 80/20, and 90/10). The nonwoven fabrics were treated with a chitosan hydrogel incorporating banana sap to enhance their properties. Scanning electron microscope (SEM) examined the surface morphology and structural integrity of the composites, while Fourier transform infrared spectroscopy (FTIR) identified chemical interactions and functional groups. Differential scanning calorimeter (DSC) revealed thermal properties, water absorbency tests demonstrated hydrophilicity, mechanical testing assessed tensile strength, and vertical flammability tests evaluated fire resistance. SEM and FTIR revealed a successful coating of chitosan hydrogel with banana sap inclusions onto the hemp/wool nonwoven fabric, forming a composite structure. DSC analysis suggests higher chitosan content and hemp fiber ratio (like 70/30) lead to increased thermal stability of hydrogel composites. Higher chitosan concentrations in the hydrogel significantly improve the flame-retardant properties of hemp/wool nonwoven fabrics by reducing char length and enhancing protective char layer formation, with banana sap further promoting charring. These results indicate that the developed composite can be effectively used in flame-retardant textiles.

Fabric-based intelligent fire-warning and flame-retardant coating: A review of advances, challenges and prospects

Fabric-based fire-warning and flame-retardant coatings could achieve dual functions of active warning response and passive fire retardancy. In contrast to conventional fire detection systems that necessitate installation at designated locations, the contact surface between the coating sensing material and the flame is substantially augmented. Therefore, it possesses crucial application value in enhancing the warning efficiency and fire safety performance of flammable substrates. This review primarily delved into the flame retardancy and fire warning of fabric coating materials. It thoroughly examined the current research status of fabric-based flame-retardant coatings and analyzed the fire-warning mechanisms of voltage-based and resistance-based coatings. Furthermore, this comprehensive review elucidated the research and current applications of various coatings based on sensing materials such as graphene oxide, carbon nanotubes, and MXene in the fire warning and flame resistance. Additionally, it is worth noting that the current functionality of fabric-based coatings is relatively limited, necessitating the incorporation of multi-functionality to adapt to various usage scenarios. In addition, it is necessary to develop large-scale coating preparation technique to achieve commercial production and combine artificial intelligence technology to achieve higher-level fire warning and flame-resistant application. Finally, the future development trend of the fabric-based coating was prospected.

The change in thermal-induced interchain distance boosts the gas barrier property of PEI-derived hollow fiber membranes

In order to fulfill diverse special applications (e.g. food packaging, anticorrosion coatings, flame retardant coatings, biomedical industry and lighter-than air applications), the superior gas barrier property is principal requirement. Based on previous researches, the gas barrier property of membranes could be improved to some extent by changing their component, chemical structure, physical property, fabrication parameters or incorporating impermeable fillers. The above-mentioned approaches provide the enhanced gas barrier property owing to increment in resistance for diffusion of tested gas. That implies the intrinsic factors of the membrane such as free volume fraction of membrane are determined effect on permeability to gas. Accordingly, present work investigated the impact of thermal treatment on enhancement of gas barrier property by manipulating the temperature in the range of 200 °C to 240 °C to adjust the orientation of molecular structure. Based on a series of analysis as well as pure gas measurement, the hydrogen permeability of as-treated membrane decreased by almost 2700 times than that of neat membrane, which is due to the absence of amorphousity. The exceptional gas barrier properties of resultant membrane exhibited great potential for special applications and paved the feasible way for other amorphous precursor to prepare the gas barrier membrane.

Bio-based flame retardant coatings for polyester/cotton fabrics with high physical properties using ammonium vinyl phosphonate-grafted chitosan complexes

Polyester/cotton (T/C) blended fabrics are widely utilized in textile due to the dimensional stability and high elasticity provided by polyester, combined with the comfort and moisture absorption offered by cotton. However, simultaneously enhancing the flame retardancy and maintaining the physical properties of T/C blended fabrics for clothing and furniture applications remains a big challenge. This study introduces a bio-based flame-retardant coating using polyelectrolyte complexes (PEC) composed of ammonium vinyl phosphonate-grafted chitosan (AMVP-g-CS). The protonation degree of the PEC coating is controlled by adjusting the pH to solidify and stabilize the complex structure, preparing bio-based PEC flame retardant T/C blended fabric. Flame retardant analysis reveals that the coated fabrics achieved a limiting oxygen index of 30.5 % and a char length of 11 mm, indicating significantly improved flame retardancy. The combustible volatile substances are significantly reduced for the coated fabrics, achieving a gas-phase flame retardant effect, and forming an expansive char layer with thermal insulation and oxygen blocking properties. Importantly, physical analysis proves that the PEC deposition improved mechanical properties, satisfactory whiteness index and hand feeling of the fabrics. This work opens up a pragmatic and industrially feasible strategy for the development of CSs in the field of flame retardant coating.

Flame-retardant coatings with ultraviolet resistance by doping KH-560 modified nano-silica into Na2SiO3/NaOH-activated copper tailings geopolymer

Copper tailings (CTs) are the industrial waste that causes resource wastage and pollution issues; recycling approaches of CTs remain challenging and are worth exploring. Herein, the Na2SiO3/NaOH-activated CTs geopolymer coating is prepared by doping melamine polyphosphate (MPP), aluminum diethyl phosphate (ADP), and nano-silica modified by silane coupling agent KH-560 (KH-560@nano-silica). The flame retardancy and ultraviolet (UV) aging resistance of the coating are evaluated through various techniques. Cone calorimeter results indicate that 4 wt% KH-560@nano-silica reduces the peak heat release rate from 84.84 to 43.98 kW·m−2 and increases the flame retardancy index from 1.00 to 6.60. Moreover, 4 wt% KH-560@nano-silica diminishes the degree of decline in flame retardancy of the coating after UV aging by 63.02 %. Thermogravimetric analysis shows that 4 wt% KH-560@nano-silica increases the temperature of 5 % weight loss and 30 % weight loss of the coatings by 42.93 % and 60.99 %, respectively. Furthermore, microscopic analysis indicates that nano-silica and the catalytic charring of CTs and flame retardants contribute to forming dense and continuous residue. According to a three-dimensional diffusion model, the activation energy (Eα) increases from 154.69 to 171.94 kJ·mol−1 at 717 ∼ 987°C. Meanwhile, the coating exhibits a formaldehyde adsorption rate of 61.79 %. In conclusion, this study expands the application scope of inorganic geopolymers in the flame-retardant industry, offering a new strategy for the high-value recovery and utilization of CTs.

Highly effective flame-retardant coatings consisting of urea-formaldehyde resin/aluminium hydroxide/boric acid for polystyrene foam: Properties and mechanisms investigation

The flame-retardant properties of expanded polystyrene (EPS) foam were enhanced by constructing a flame-retardant coating on its surface using melamine modified urea-formaldehyde resin (MUF), H3BO3, and Al(OH)3 as raw materials. A coating consisting of an equal proportion of H3BO3 and Al(OH)3 demonstrated superior mechanical properties, flame-retardant properties, and smoke suppression ability. Additionally, this coating increased the compressive strength of EPS material by 43.30 %, raised the carbon residue from 0.14 % to 32.4 %, elevated the limiting oxygen index to 37.4 %, and achieved a vertical combustion rating of V-0 according to UL-94 standards. These improvements were accompanied by a reduction in peak heat release rate by 59.36 %, total smoke production by 51.99 %, maximum smoke density by 80.13 %, and smoke density rating by 89.52 %. Furthermore, the coated material exhibited satisfactory water resistance, thermal insulation, and transparency. Simulation results show that the MUF/H3BO3/Al(OH)3 coating system generated various metal and non-metal compounds during combustion along with NOx, COx, and H2O gases. The beneficial flame-retardant effect of the coating can be attributed to the hybrid flame-retardant effect of H3BO3 and Al(OH)3 in both the gas and condensed phases.

Low temperature carbonization and synergistic flame retardancy of cotton fabric coated by phosphorus‑nitrogen flame retardants

To solve the problems of flammability and smoldering of cotton fabric, its flame-retardant finishing was executed with biomass wool keratin (WK) and cyclic phosphate ester (CPE) through the soaking and baking process. The synergistic mechanism of WK low-temperature melting and CPE catalytic dehydration prompted the formation of protective carbonization layer on cotton fabric surface, and this protective layer reduced its pyrolysis rate, inhibited the production of combustible materials and improved its flame retardancy. The results of synchronous thermal analysis indicate that the initial decomposition temperature of WK and CPE is lower than that of cotton fabric, and they precede the endothermic degradation before fabric main body. This effectively promotes the low-temperature carbonization of cotton fabric and inhibits its pyrolysis. The initial decomposition temperature of WK/CPE treated fabrics advances by 47.9 °C–97.8 °C, presenting significant low-temperature carbonization trend. Moreover, they form 3.0 %–20.0 % aromatic structural char before the pyrolysis of cotton cellulose due to the low-temperature dehydration and carbonization reactions. The damage length after vertical burning is only 4.0 cm for treated fabric with five layers, its after-flame and smoldering disappear, and its limiting oxygen index value increases to 28.7 %. This research provides an effective idea for the flammability and smoldering problems of cotton fabric.

Flame-Retardant Coating on Wood Surface by Natural Biomass Polyelectrolyte via a Layer-by-Layer Self-Assembly Approach

In this study, environmentally friendly and low-cost biomass materials were selected as wood flame retardants. Three polyelectrolyte flame-retardant coatings made from chitosan (CS), tea polyphenols (TP), soybean isolate protein (SPI), and banana peel powder (BBP) were constructed on wood surfaces by layer-by-layer (LBL) self-assembly. The results of SEM-EDS and FT-IR analyses confirmed the successful deposition of CS-TP, CS-SPI, and CS-BPP on the wood surface, and the content of N element increased. The TG results showed that the initial decomposition temperature and the maximum thermal decomposition temperature of the coated wood specimens decreased, while the char residue increased significantly. This is due to the earlier pyrolysis of CS-TP, CS-SPI, and CS-BBP. This shows that the three polyelectrolyte flame-retardant coatings can improve the thermal stability of wood. The combustion behavior of the wood specimen was observed by exposure to combustion; the coated wood could self-extinguish within a certain period of time after ignition, and the flame-retardant performance was improved to a certain extent. SEM and EDS characterization analyses of the carbon residue after combustion showed that the coated wood charcoal layer was denser, which could effectively block heat and combustible gas.

Synergistic effect of coal gangue on intumescent flame retardants

Abstract In order to improve the flame retardant properties of wood plywood, intumescent flame retardant coatings were prepared using melamine, borate, pentaerythritol and urea as the basic formulations and gangue as a modified additive. The flame retardancy of the samples was characterized using a cone calorimeter, scanning electron microscope, X-ray diffraction and thermogravimetric analysis. In addition, the study investigated the effect of gangue content on the properties of the prepared coatings. The results show that the doping of gangue in intumescent flame retardant coatings can improve the flame retardant effect of the coatings. Specifically, when the mass fraction of gangue was 8 wt%, the exothermic rate, total smoke production and total exothermic amount of the coating were significantly reduced. Moreover, the addition of gangue promoted the formation of a continuous and dense carbon layer structure during the combustion process of the coating, which produced a molten substance that effectively isolated oxygen and heat, thus strengthening the fire-retardant and heat-insulating properties of the coating. The results of this study provide valuable insights into the development of flame retardant coating formulations for wood plywood.

ИССЛЕДОВАНИЕ ПРОЦЕССОВ ТЕРМИЧЕСКОЙ ДЕСТРУКЦИИ ОГНЕЗАЩИТНЫХ ВСПУЧИВАЮЩИХСЯ СОСТАВОВ МЕТОДОМ ИНФРАКРАСНОЙ СПЕКТРОСКОПИИ

An infrared spectroscopy study of changes in chemical composition as a result of thermal destruction of flame-retardant bulging coatings based on an acrylic organo-soluble binder, as well as on a vinyl water-soluble binder, was carried out. Absorption bands characteristic of flame retardant components and binders included in the coatings under study have been established. The absorption bands undergoing the most significant changes at temperatures from 100 to 500 °C are selected and the optical densities of the selected bands are calculated. Using the ratio of the optical densities of the selected absorption bands, spectral criteria for each temperature were calculated and calibration dependences were constructed, which subsequently allowed them to be used to determine the degree of thermal damage to the studied flame retardant coatings. It is shown that the IR spectroscopy method will allow solving issues related to the study of flame-retardant bulging coatings and their residues formed as a result of temperature exposure in a fire.

Characteristics of phosphorus‑nitrogen based flame-retardant monomers for UV-curable coatings on battery PET pouches

In this study, photocurable monomers containing phosphorus–nitrogen groups were employed alongside UV curing technology to develop flame-retardant (FR) coatings pouch-type battery cells made from polyethylene terephthalate (PET). Three different monomers were synthesized: a phosphorus-containing urethane acrylate monomer (DUPPO), a phosphorus–nitrogen-containing urethane acrylate monomer (DA-Pi-U), and a phosphazene-containing phenyl methacrylate crosslinker (CP-PMA). These monomers, recognized for their flame-retardant properties, were utilized in binary and ternary coating formulations that were effectively cured via a UV-curing process. The molecular architectures of the synthesized monomers were verified through 1H and 31P nuclear magnetic resonance spectroscopy. The rheological curing behavior of the coating solutions was assessed using an oscillatory rheometer. In addition, the reactivity of the FR coating system was examined via Fourier transform infrared spectroscopy. The thermal and flame-retardant characteristics of the FR coatings were confirmed through thermogravimetric analysis, Raman spectroscopy, limiting oxygen index measurements, and scanning electron microscopy. The ternary FR coating system with CP-PMA exhibited superior thermal stability, flame retardancy, crosslinking density, and mechanical robustness, making it suitable for PET pouches. Furthermore, optimal coating conditions for the slot coating process were determined using a viscocapillary model, enhancing practical applicability in industrial settings.

Smoke Suppression Properties of Fe2O3 on Intumescent Fire-Retardant Coatings of Styrene–Acrylic Emulsion

The intumescent flame-retardant coatings were prepared using ammonium polyphosphate (APP), pentaerythritol (PER), melamine (MEL), styrene–acrylic emulsion, and iron oxide yellow (FeOOH) as the base material. A cone calorimeter (CCT), smoke density meter (SDA), and scanning electron microscope (SEM) were employed to investigate the smoke suppression and flame retardancy of FeOOH in intumescent fire-retardant coatings. The thermal degradation performance of intumescent fireproofing coatings with varying FeOOH content was investigated through thermogravimetric analysis (TGA). The structure of the carbon slag in the CCT test was analyzed using a scanning electron microscope (SEM). The results of the cone calorimeter (CCT) experiments demonstrated that FeOOH significantly reduced the heat release rate (HRR), total heat release rate (THR), smoke production rate (SPR), and total smoke release rate (TSR) of the coating, while simultaneously increasing the carbon residue rate of the coating. The smoke density analysis (SDA) results demonstrate that adding FeOOH can effectively reduce smoke generation, regardless of whether a pilot flame is used. TGA results demonstrate that FeOOH can enhance the weight of coke residue at elevated temperatures. SEM results indicate that incorporating FeOOH resulted in a more compact coke residue. According to these findings, among all the samples, those containing 2 wt% FeOOH showed low levels of HRR, THR, SPR, and TSR and high levels of SOD, which proves that FeOOH can be used as a smoke inhibitor in flame-retardant coatings.

Analysis of the flame retardancy effect of boron-containing compound on polyester-cotton blended fabric

Flame-retardant finishing of textile materials is crucial for ensuring human safety and mitigating fire hazards. Though various textile fibers have inherent flame-resistant properties, cotton fiber has a higher affinity to burn. This research focused on developing non-durable FR treatments for cotton-rich polyester-cotton (T/C) blended products economically, using boron-containing compounds. Because of the high melting point use of borax on T/C fabric reduces the fabric's flammability. Boric acid was also used as an auxiliary substrate and Di-sodium hydrogen phosphate dihydrate was used for its cleaning and softening properties. Borax and boric acid create a layer of char when burned and stop the flame. We used the impregnation method for this finishing process. After the chemical finish on different types of T/C fabric, we completed different types of tests like 450 flame retardant, LOI, SEM, breaking strength, drapability, crease recovery, and water vapor transmission tests, and found the desired properties. It increased the flame retardancy and crease recovery properties but the slight reduction of the fabric strength was noticed in case of excessive coating. Water vapor transmission property also reduced gradually with the increase of chemical concentration. Since the chemicals are available in the local market and lower in cost than common FR chemicals, it is more economical.

Development of a pyrolysis reaction model for epoxy based flame retardant composites: Relationship between pyrolysis behavior and material composition

This paper presents a methodology to develop a pyrolysis reaction model that captures the flammability behavior of epoxy-based intumescent flame retardant coatings (EP/IFR) as a function of material composition. This approach adopted Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Microscale Combustion Calorimetry (MCC) experiments as well as the inverse modeling of the experimental results using ThermaKin2Ds and COMSOL Multiphysics modeling framework. The interactive reactions between EP and IFR were identified and quantified in the resulting lumped model, which is based on fitting of experimental data. It was found that the developed model was able to reproduce the TGA/DSC/MCC data within the prescribed criteria for EP/IFR blends with different material compositions. The model’s extrapolating capability was further validated through accurately predicting the experimental TGA data under different thermal conditions and for blends with different IFR ratios which were not used for model development. Additional TG-FTIR and XPS experiments were conducted to quantify the effect of IFR additive on the evolution of gaseous products and char formation. With a higher ratio of IFR, the amount of fuel dilution gases (i.e., CO2, NH3) was increased and the amount of combustible organic gaseous products was reduced. This work provides the core subset parameters for comprehensive pyrolysis modeling and enables the intelligent design of EP/IFR coatings with enhanced flame resistance.

Construction of composite self-assembly coating based on chitosan for enhancing the flame-retardant and antibacterial performances of cotton fabric

In this work, the step-by-step dip-coating (SBS) method was used to effectively improve the drawback of LBL by reducing the construction of a multilayer polyelectrolyte. Bio-based flame retardants, phytic acid (PA), and chitosan (CS) were further self-assembly on the surface of cotton fabric treated by epichlorohydrin-modified aramid nanofibers (AEP), ionic liquid (IL), and Cu ion. The pure cotton fabric was immersed in each dipping liquid only once, improving fire safety and antibacterial performance. The treated cotton self-extinguished with a 59 mm char length in the vertical flammability test, and the limiting oxygen index (LOI) value increased from 18.5 % to 38.5 %. The result of the cone calorimeter test (CCT) revealed that the fire hazard of flame-retardant cotton noteworthy declined (e.g., ~44.1 % and 55.4 % decline in peak heat release rate (pHRR) and total heat release rate (THR)). Conspicuously, the treated cotton exhibited a remarkably inhibiting effect on E. coli and S. aureus activity. The cotton fabric after flame-retardant finishing exhibited excellent fire safety and antibacterial performance.

A Novel Intumescent MCA-Modified Sodium Silicate/Acrylic Flame-Retardant Coating to Improve the Flame Retardancy of Wood.

The incompatibility between inorganic flame retardants and organic acrylic coatings represents a significant challenge that requires resolution. This work selected environmentally friendly organic aqueous acrylic coatings as the substrate, sodium silicate hydrate as the inorganic flame retardant, and melamine cyanurate (MCA) as the flame-retardant modifier and the flame-retardant co-modifier, with the objective of improving the dispersion and flame-retardant properties of sodium silicate hydrate in the aqueous acrylic coatings. Subsequently, the sodium silicate/MCA/waterborne acrylic acid flame-retardant coating was prepared. The flame-retardant treatment was then applied to poplar veneer in order to create a flame-retardant poplar veneer. The dispersion of the flame-retardant coating was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), and X-ray diffractometry (XRD). Furthermore, the flame-retardant properties of the flame-retardant poplar veneer were analyzed by thermogravimetry (TG), limiting oxygen index (LOI), and cone calorimeter. The results demonstrated that the MCA-modified sodium silicate flame retardant was well dispersed in aqueous acrylic coatings. The results of the flame-retardant properties of the poplar veneer indicated that the ignition time of the 9% flame retardant-treated poplar veneer was increased by 122.7%, the limiting oxygen index value was increased by 43.0%, and the peak heat release rate (pHRR), the peak total heat release rate (pTHR), and the peak mass loss rate were decreased by 19.9%, 10.8%, and 27.2%, respectively, in comparison to the non-flame retardant-treated poplar veneer. Furthermore, the residual char mass increased by 14.4%, and the residual char exhibited enhanced thickness, density, and regularity. The results demonstrated that MCA was an effective promoter of sodium silicate dispersion in acrylic coatings. Furthermore, the sodium silicate/MCA/waterborne acrylic flame-retardant coating significantly enhance the flame retardancy of wood, and its flame retardant mechanism was consistent with the synergistic silicone-nitrogen expansion flame-retardant mechanism. This work presents a novel approach to enhancing the dispersion of inorganic flame retardants in organic coatings, offering a valuable contribution to the advancement of research and application in the domains of innovative flame retardant coatings and flame retardant wood.

Low temperature carbonization, smoke suppression and durable flame retardancy of cotton fabric spray-assisted coated by phosphorus nitrogen silicon composite system

To solve the problems of flammability, smoldering, smoking and flame retardant durability of cotton fabric, flame retardant fininshing was executed using spray assisted self-assembly method, and P/N/Si synergistic flame retardant system was constructed by polyethylene imine (PEI), phytic acid (PA) and 3-aminopropyltriethoxysilane (APTES). Cotton cellulose carbonized at low temperature prompting by PA catalytic effect, and this cooperated with PEI thermal decomposition to endow cotton fabric with flame retardancy and smoking suppression by reducing its pyrolysis rate at high temperature and lessening combustible products. Meanwhile APTES as silane coupling agent further improved its flame retardant durability and smoke suppression effect. The synchronous thermal analysis results indicate that cotton fabrics treated by PA/PEI/APTES composite system present significant low-temperature carbonization trend, and their initial decomposition temperatures advance by 46.5℃-75.9℃. Moreover, they form 4.6 %-44.9 % aromatic structure char through dehydration and carbonization reactions during the low-temperature carbonization process, improving their thermal stability at high temperature, and their after-flame and smoldering phenomena disappear. The damaged length of treated fabric with five layers reduces to 5.0 cm, its limiting oxygen index reaches 33.7 %, and it presents excellent flame retardant durability and smoke suppression effect. This low-temperature carbonization mechanism possesses importantly innovative significance for the flame retardant finishing of cotton fabric, and it not only more actively guides the selection of flame retardants to make them match with the material required, but provides a new thinking method for flame retardant material research in the future.

Construction of sustainable and highly efficient fire-protective nanocoatings based on polydopamine and phosphorylated cellulose for flexible polyurethane foam

Layer-by-layer (LBL) self-assembly is an effective strategy for constructing fire-resistant coatings on flexible polyurethane foam (FPUF), while the efficiency of fire-resistant coatings remains limited. Therefore, this study proposes an in situ flame retardancy modification combined with LBL self-assembly technology to enhance the efficiency of flame retardant coatings for FPUF. Initially, polydopamine (PDA) and polyethyleneimine (PEI) were employed to modify the FPUF skeleton, thereby augmenting the adhesion on the surface of the skeleton network. Then, the self-assembly of MXene and phosphorylated cellulose nanofibers (PCNFs) via the LBL technique on the foam skeleton network formed a novel, sustainable, and efficient flame retardant system. The final fire-protective coatings comprising PDA/PEI and MXenes/PCNF effectively prevented the collapse of the foam structure and suppressed the melt dripping of the FPUF during combustion. The peak heat release rate, the peak CO production rate and peak CO2 production rate were reduced by 68.6 %, 61.1 %, and 68.4 % only by applying a 10-bilayer coating. In addition, the smoke release rate and total smoke production were reduced by 83.3 % and 57.7 %, respectively. This work offers a surface modification approach for constructing highly efficient flame retardant coatings for flammable polymeric materials.