Smoke Release Rate Research Articles

The effects of zinc hydroxystannate/boron nitride hybrids and aluminum diethylphosphinate on flame retardancy and smoke suppression of styrene–butadiene rubber composites

AbstractAs one of the three general rubbers, styrene–butadiene rubber (SBR) is widely used in industrial products such as tires and cables. However, SBR has the disadvantages of flammability and low thermal conductivity, which limits its application in industry. In order to improve the flame retardancy and thermal conductivity of SBR, zinc hydroxystannate/boron nitride hybrids (ZHS@BN) were successfully prepared by in‐situ growth on BN. ZHS@BN was successfully prepared as determined by Fourier transform infrared spectroscopy, x‐ray diffraction, scanning electron microscopy and thermogravimetry. When 3 phr ZHS@BN and 12 phr aluminum diethylphosphinate (ADP) were added, the limiting oxygen index value of SBR composites reached 28.4%. Compared with pure SBR, their peak heat release rate and peak smoke release rate decreased by 59.2% and 50.6%, respectively. Through the analysis of the flame‐retardant properties and carbon residue of the SBR composites, it was proved that there was a good synergy between ZHS@BN and ADP to improve the flame‐retardant properties of SBR.

Synthesis of functionalized Salen‐Ni‐based polyphosphazene flame retardant and its performance study

AbstractA novel functional copulatory polyphosphazene microsphere (Salen‐PZN‐Ni‐KH550) was successfully synthesized via reaction of the surface of Salen‐Ni‐based polyphosphazene (Salen‐PZN‐Ni) with 3‐aminopropyltriethoxysilane, and it was introduced as an additive flame retardant in pure epoxy resin (EP). Thereafter, the effects of the prepared flame‐retardant Salen‐PZN‐Ni‐KH550 on thermal stability, combustion performance, and flame‐retardant mechanism of the EP system were studied in detail. The addition of Salen‐PZN‐Ni‐KH550 led to a significant increase in thermal stability and formation of carbon residue in the EP at a temperature of 800°C. The results showed that the addition of 5 wt% Salen‐PZN‐Ni‐KH550 lowered the maximum heat release rate, as well as the peak smoke release rate by 28.83% and 25.71%, respectively. This resulted in a significant improvement in the fire safety of EP. Additionally, the introduction of Salen‐PZN‐Ni‐KH550 considerably inhibited the evolution of the toxic gas CO and of other volatile products that are produced during the decomposition process of EP. The results of study suggest that mechanism of the flame retardant may be associated to gas‐phase quenching, incombustible gas release, synergistic catalytic carbonization effect and to the formation of components with extremely high thermal stability. The fire safety of EP composites and the reduction of toxic gases can be attributed to the synergistic effects of nickel, APTES, and polyphosphazene microspheres. The development of the new flame‐retardant Salen‐PZN‐Ni‐KH550 is an effective strategy to improve the fire resistance of polymers.

Coating Composites Based on Polyurea Elastomers with Increased Fire Resistance and Their Use as Roofing Systems

This paper presents the results of tests on elastomer coatings based on polyurea–polyurethane formulation with increased fire parameters. Coatings modified with flame retardants: bis(phenylphosphate) resorcinol (RDP), trischloropropyl phosphate (TCPP), and aluminum hydroxide (ATH) were tested. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA/DTG) were used to investigate the structure and thermal stability. The effectiveness of resorcinol bis(phenylphosphate) (RDP), tris chloropropyl phosphate (TCPP), and aluminum hydroxide (ATH) on heat release rate (HRR), smoke release rate (RSR), and oxygen consumption was evaluated using cone calorimetry. The cone calorimetry results were correlated with the mechanical properties of the coatings. The cone calorimetry analysis showed suitable organophosphorus flame retardant (FR) performance, significantly decreasing HRR and oxygen consumption. Additionally, 15% TCPP caused a reduction of HRR by over 50%, obtaining 211.4 kW/m2 and pHRR by over 55%, reaching 538.3 kW/m2. However, organophosphorus flame retardants caused a significant deterioration of mechanical properties simultaneously. Introducing a mixture of two FRs (RDP/TCPP) resulted in obtaining a coating with improved fire resistance and maintained good mechanical strength. The polyurea–polyurethane coating, modified with a mixture of two RDP/TCPP retardants (10:5), was simulated for the burning of roof systems. The result of the simulation was assessed positively. Thus, finally, it was confirmed that the proposed polyurea–polyurethane coating achieved the assumed flame retardant level.

The coating based on phenolic resin gives rigid polyurethane foam excellent flame retardant properties

AbstractA flame retardant coating was designed and synthesized using phenolic resin (PF), 9,10‐dihydro‐9‐oxa‐10‐phosphazephenanthrene‐10‐oxide (DOPO), and nano‐SiO2 as raw materials. The coating is applied to the surface of rigid polyurethane foam (RPUF) to give it a flame retardant effect. Based on the excellent adhesion of PF, the coating effectively suppresses heat transfer, and the synergistic effect of DOPO and nano‐SiO2 improves the flame retardancy of RPUF. In addition, vertical combustion experiments have shown that when the ratio of DOPO to nano‐SiO2 is 2:1, there is no dripping, the flame is self‐extinguishing, and the internal structure remains basically unchanged, resulting in the best flame retardant effect. The cone calorimetric test shows that the coating can effectively reduce the total heat release and heat release rate of the substrate, and the smoke release rate and total smoke release data show that its smoke suppression effect is significantly improved. Thermogravimetric analysis shows that the coating can effectively improve the residual carbon rate of RPUF, and its mechanical properties are good. This study confirms that coatings based on PF/DOPO/Nano‐SiO2 can effectively improve the flame retardancy of RPUF, providing a potential direction for the development of green insulation materials.

Fire Risk Rating Assessment for Wood Specimens Coated with Flame Retardant

Chung's equations-II, -III, and -IV were applied to evaluate the fire risk and fire risk ratings of flame retardants. As an example, a wood specimen coated with a flame retardant was selected and tested using a cone calorimeter according to the ISO 5660-1 standard. The external heat flux was fixed to 50 kW/m2. Fire performance index-III used three variables to evaluate the initial fire risk: the time to ignition, first peak heat release rate, and first peak smoke release rate. Fire growth index-III was calculated using the first peak heat release rate, peak smoke production rate, and time to reach the first peak smoke production rate. This index is a standardized fire hazard category with poly(methyl methacrylate) as the reference material. The fire risk rating index, fire risk index-IV, is expressed as the value obtained by dividing the fire growth index-III by fire performance index-III. In this study, the methodology for fire risk rating evaluation is discussed.

Enhanced mechanical performance and fire resistance of poplar wood: Unilateral surface densification assisted with N/P doped acrylic resin impregnation

It is difficult to significantly improve the mechanical performance and fire-resistance of fast-growing wood without increasing its density. In this study, a modified poplar wood (USD-RA-W) with low-density, high dimensional stability, high mechanical strength, and fire resistance was successfully prepared by unilateral surface densification assisted with the impregnation of waterborne acrylic resin (WAR)/ammonium phytate (APA). The flexural and impact strength values of USD-RA-W increased by 52% and 48%, respectively, compared to the control samples (C-W). The surface hardness and wear resistance of USD-RA-W were also significantly improved, with a 132% increase in hardness and a 22% reduction in weight loss relative to C-W. The improvement in mechanical properties is attributed to the synergistic effects of surface densification and impregnation modification of APA-doped acrylic resin. The in-situ-cured resin network provides excellent dimensional stability by fixing the spring-back of the densified surface of the material. USD-RA-W shows significantly improved fire retardancy due to the introduction of bio-based APA. UL-94 analysis results show that the fire-retardant grade of the USD-RA-W passed V-0 and the limited oxygen index reached 50%. Cone calorimeter test results indicate that the total heat release rate and smoke release rate of the experimental group decreased by 32% and 77%, respectively, while the char residue reached 41%. A simple and green physic-chemical method for the preparation of high-performance USD-RA-W was established in this study. The proposed treated wood may be applicable in structural building materials and interior decoration fields.

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.

Flame retardancy and combustion performance of polysaccharide fabrics: A comparison on cotton and calcium alginate fabrics

Cotton and calcium alginate (CA) fibers are both polysaccharide-based fibers, but they possess different flame retardancy. The detailed comparisons on flame retardancy and combustion behavior of polysaccharide fabrics are of interest. In this study, the difference between the fabrics made of these two fibers in the combustion process, pyrolysis products and the morphology and chemical structures of char residues were performed by vertical burning, thermal gravimetric analysis, Fourier Transform Infrared Spectrometer (FTIR) and scanning electron microscopy. Compared with cotton fabric, CA fabric had no after-flame when it was burned vertically, and the smoldering time was longer. Especially, the smoke release rate, peak heat release rate and total heat release were much lower versus cotton fabric, indicating that CA fabric had much lower fire hazards than cotton fabric. The results of thermogravimetric analysis coupled with FTIR (TG-FTIR) suggested that CA fabric exhibited a different thermal degradation pathway versus cotton fabric. Under the same quality, CA fabric produced more char residues after combustion, and chrysanthemum-like calcium oxide were generated on the surface of char residues as protective barrier, leading to the enhanced flame retardancy of CA fabric.

Analysis of Thermal Degradation Kinetics of POM under Inert and Oxidizing Atmospheres and Combustion Characteristics with Flame Retardant Effects.

Degradation behavior of combustible fuel is the core factor in determining combustion characteristics. To investigate the effect of ambient atmosphere on the pyrolysis process of polyoxymethylene (POM), the pyrolysis mechanism of POM was studied with thermogravimetric analyzer tests and Fourier transform infrared spectroscopy tests. The activation energy, reaction model, and estimated lifetime of POM pyrolysis under different kinds of ambient gases have been estimated in this paper based on different results of the kinetics. The activation energy values, obtained with different methods, were 151.0-156.6 kJ mol-1 in nitrogen and 80.9-127.3 kJ mol-1 in air. Then, based on the Criado analysis, the pyrolysis reaction models of POM in nitrogen were found to be mastered by the "n + m = 2; n = 1.5" model, and by the "A3" model in air. The optimum processing temperature for POM was estimated, with a range from 250 to 300 °C in nitrogen and from 200 to 250 °C in air. IR analysis revealed that the significant difference in POM decomposition between N2 and O2 atmospheres is the formation of isocyanate group or carbon dioxide. Combustion parameters of two POMs (with and without flame retardants) obtained using cone calorimetry revealed that flame retardants can effectively improve the ignition time, smoke release rate, and other parameters of POM. The outcomes of this study will contribute to the design, storage, and transportation of polyoxymethylene.

Flame-retardant and antibacterial properties of cotton fabrics treated by epichlorohydrin-modified aramid nanofibers, ionic liquid, and Cu ion

To meet the demands of reducing the serious illness caused by the growth of bacteria and the severe life-threatening due to interior fabric fire, the attention to antibacterial flame-retardant cotton fabrics has reached an unprecedented height. In this work, a simple step-by-step dip-coating method was applied for the multifunctional cotton based on epichlorohydrin-modified aramid nanofibers (AEP), ionic liquid (IL), and CuSO4. Cot/AEP/IL/Cu exhibited low flammability with a limiting oxygen index (LOI) improving from 18.5% to 28.5% and high flame retardancy (e.g., ∼43.7% and 41.7% decline in peak heat release rate (pHRR) and total heat release rate (THR)). Noticeably, the Cot/AEP/IL/Cu revealed conspicuous smoke suppression and toxic reduction property compared with Cot/AEP/IL (e.g., ∼77.0% decline in peak smoke release rate (pSPR) and 40.5% in total CO production (TCOP)). In addition, the antibacterial property of treated cotton was investigated by the agar diffusion plate method. Due to the presence of Cu ion, Cot/AEP/IL/Cu remarkably restrains the activity of E. coli and S. aureus. This work prepared a multifunctional cotton fabric integrated with flame-retardant, smoke suppression, toxicity reduction, and antibacterial in a straightforward way, which endows promising applications in many fields.

Highly flame-retardant vinyl ester resins with well-balanced comprehensive performance

Flame-retardant vinyl ester resins (VER) have long been studied, however, very few flame retardants can efficiently improve the flame retardancy of the resin without deteriorating their other performance. In this work, a kind of liquid phosphorus-containing 1-vinylimidazole salt (called VC) was synthesized in a facile way with a very high yield. Then, VC was used as the flame-retardant crosslinking agent to obtain flame-retardant VER. Curing behaviors, flame retardancy, thermal stability, thermomechanical properties, and mechanical performance of the resin were investigated. VC had good compatibility with VER and the mixture presented a relatively low viscosity. VC/VER showed a high curing activity and can be efficiently cured in moderate conditions. VC was incorporated into the resin mainly by ionic bonds, by which interchain ionic interactions were constructed in the resin. With only 15 wt% additions of VC, the cured VC15/VER easily passed the UL 94 V0 rating and achieved a limiting oxygen index value of 32.7%. In the cone calorimetric test, VC15/VER severally presented a reduction in the peak heat release rate, total heat release rate, and total smoke release rate of 67.8%, 17.1%, and 27.3% compared to VER. VC15/VER showed good thermal stability, had a glass transition temperature of 151 °C (that of VER was 137 °C), and achieved high mechanical performance that can be comparable to VER. Hence, this work proposes a facile strategy for producing flame-retardant thermosets with well-balanced comprehensive performance, which exhibits potential in coatings, composites, and laminates for versatile applications.

Phase change material microcapsules with DOPO/Cu modified halloysite nanotubes for thermal controlling of buildings: Thermophysical properties, flame retardant performance and thermal comfort levels

Although the microencapsulated phase change material (MPCM) with organic core-shell structure is an effective means to encapsulate phase change material (PCM), it has the defects of low thermal conductivity and flammability. Herein, the flame retardant halloysite nanotubes (c-HNTs) doped by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and Cu nanoparticles were successfully inserted in the MPCM to form a highway to heat transfer. The related examination and surface morphology showed that the DOPO structure anchored by Cu nanoparticles was grafted on the surface of halloysite nanotubes (HNTs) and the c-HNTs were successfully embedded in MPCM. The thermogravimetric analysis (TGA) proved that c-MPCM has the best thermal stability when compared to other samples, which is caused by the presence of c-HNTs. The differential scanning calorimetry (DSC) test indicated that MPCM delays the heat transfer to the capric acid while the HNTs improve this situation as thermal conduction channels. Then, the MPCM samples were added to the epoxy resin (EP). In the cone calorimetry test, we found that the heat and smoke release rate of EP composite is obviously reduced. Finally, the temperature control ability test of MPCM demonstrated that the EP composite with c-HNTs has the minimum temperature fluctuation. These properties will greatly stimulate the application of c-MPCM in insulation materials.

Design lignin doped with nitrogen and phosphorus for flame retardant phenolic foam materials

Developing lignin-based flame retardants for phenolic foam with exceptional flame retardancy and mechanical performances remains a huge challenge due to complicated chemical structure and unstable chemical activity of lignin. In this study, nitrogen‑phosphorus doped lignin flame retardant (NP-LMDL) was prepared by modifying reactive lignin with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and triethylenetetramine (TETA), which was utilized to partially replace phenol to prepare flame retardant phenolic foams (NP-LMDLPFx). The results showed that nitrogen‑phosphorus doped lignin enhanced the flame retardant performance and compressive strength of the foam. The limiting oxygen index (LOI) and compressive strength of NP-LMDLPF15 increased by 33.3% and 43.7% comparing with pure phenolic foam (PF). The peak heat release rate (pHRR) and peak smoke release rate (pRSR) decreased by 48.0% and 53.2%. Moreover, the structure and elemental constitution of char residues were analyzed to discuss the flame retardant mechanism of nitrogen and phosphorus in foam. Nitrogen and phosphorus in NP-LMDLPFx worked together to promote polymers carbonization and generate rich nitrogen and phosphorus char residue layer, insulate heat and oxygen to play the role of flame retardant.

The Impact of Wood Fibers in Composite Panels Made from Recycled Fiberglass Wind Turbine Blades

The utilization of wind power has increased almost exponentially during the last decade, leading to the growth in both the number and size of wind turbines. Modern turbine blades are typically made of fiberglass sandwiched around a balsa wood (BW) core. With an increase in the use of wind energy a collateral issue of what to do with the large and voluminous wind turbine blades (WTB) that reached end-of-life has arisen. Through previous research, we developed a recycling process that will keep these turbine blades out of the landfill by considering recycled wind turbine blades as a feedstock for second generation composite panels. The objective of this research is to further the research by understanding the effect that different compositions of wood and fiberglass have on the properties of these panels. Through testing, it was found that the addition of balsa wood increases the modulus of rupture (MOR) and the modulus of elasticity (MOE). The internal bonding (IB) strength values are well above that of typical particle board. All panels tested were visibly more resistant to water sorption than typical particle board. The thermal conductivity for all samples was within the typical range for particleboard. Fire test result indicates that the addition of balsa wood increases the heat and visible smoke release rate of composites.

A novel sustainable strategy of upcycled waste polyphenylene sulfide filter bag: From waste polyphenylene sulfide powder to char‐forming agent for flame retardant epoxy

AbstractPolyphenylene sulfide (PPS) filter bag is widely used in the field of high temperature filtration of coal dust because of its high temperature resistance and stable chemical properties. However, as nondegradable solid waste, incineration is main solution for waste PPS filter materials which also brings harm to the environment. To achieve green recycling and efficient utilization of waste PPS filter material, waste PPS is utilized as the charring agent together with ammonium polyphosphate (APP) to form a compound flame retardant to improve flame retardancy of epoxy resin (EP). Due to the excellent char‐forming ability of PPS, good performance of EP/APP/PPS composites is obtained in the rigorous combustion test. When the mass ratio of APP and waste PPS is 3:1 and the total load is 15 wt%, EP/IFR3 composite can pass the UL‐94 V‐0 rating, and its LOI increase to 28.1%. Furthermore, cone calorimetry tests presented its peak heat and smoke release rates were reduced by 49.9% and 63.6% compared with neat EP, respectively. Residual carbon analysis shows that this system is mainly a condense‐phase flame‐retardant mechanism. In addition, due to poor dispersion and compatibility, the flexural performance and thermal stability are destroyed to a certain extent.

Cavity expansion and nanohybrid copper phytate@halloysite coated with polyphosphazene for reducing smoke release and fire hazard of epoxy resin

Halloysite (Hal) nanotubes have become a good nano-carrier of flame retardant systems. In the present work, cavity expansion of Hal was achieved by etching with sulfuric acid to improve its loading capacity. Then, copper phytate was synthesized and encapsulated in the Hal to obtain Phyt-Cu@Hal. Finally, a sulfonyldiphenol-containing polyphosphazene derivative (PZS) was polymerized and wrapped on Phyt-Cu@Hal external surface to form a hierarchical nanohybrid structure (Phyt-Cu@Hal@PZS). Herein, Phyt-Cu encapsulated in Hal acts as catalyzing and char-forming agents while the wrapped PZS acts as an interfacial compatibilizer which can improve the dispersion and flame retardancy of Phyt-Cu@Hal@PZS in the EP matrix. The flame retardancy and smoke suppression of the corresponding EP nanocomposites were significantly enhanced due to the synergistic effect of Phyt-Cu@Hal@PZS. After adding 5 wt% Phyt-Cu@Hal@PZS, the peak heat release rate and smoke release rate were reduced maximally by 34.3% and 42.1%, respectively. Moreover, the char residue was also greatly enhanced which is 97.3 times higher than that of neat EP. The flame retardant mechanism of Phyt-Cu@Hal@PZS was assumed that the Phyt-Cu immobilized within the Hal could distinctly inhibit the flammable pyrolysis products; the external PZS layer promotes the char formation of EP matrix; the nanoscale combination of Phyt-Cu, Hal and PZS could further enhance the catalyzing carbonization to produce a physical barrier effect.

Boron-containing ionic liquid functionalized Mo-MOF/graphene oxide hybrid for improving fire safety and maintaining mechanical properties for epoxy resin

A molybdenum-based metal organic framework (Mo-MOF) and graphene oxide (GO) hybrid functionalized with boron-containing ionic liquid ([BMIM]BF4) (GMB) was reported to effectively improve the fire safety and mechanical property of epoxy resin (EP). When 3 wt% GMB was added, the CO production rate, peak heat release rate and peak smoke release rate of EP composites decreased by 55.88%, 52.10% and 40.12%, respectively. The flame retardant mechanism was the combination of catalytic carbonization ([BMIM]BF4 and Mo-MOF), physical barrier effect (GO) and gas phase dilution (H2O and NH3 in gas production). Meanwhile, the incorporation of [BMIM]BF4 endowed EP composites with excellent mechanical properties.

Crystallization of sodium metaborate on the surface of layered double hydroxide imparts high flame retardancy properties to epoxy coatings

To address the phenomenon of rapid fire spread in high-rise steel buildings, this paper used the in situ growth method to crystallize sodium metaborate (SMB) on the surface of layered double hydroxide (LDH) and grafted Ti-O onto LDH@SMB hybrid material by hydroxyl action. The synthesized LDH@SMB@Ti (LST) hybrid material was then doped into epoxy resin (EP) to prepare a composite coating. The fire test showed that the LST/EP coating makes the steel plate reach a stable temperature in a shorter time, so that the plate temperature did not continue to rise, and the temperature on the back side of the plate was stabilized at 172.9 °C, which was 87.4 °C lower compared to pure EP. This proves that the LST material gives the coating stronger fire retardant properties upfront and strengthens the continuous insulation ability of the char layer. Cone calorimeter tests showed that the total heat release rate (THR) of LST/EP was reduced by 47.3% and the total smoke release rate (TSR) was reduced by 45.4%, proving the excellent fire and smoke suppression performance of LST/EP. In the expansion performance test, the expansion height and expansion rate of LST/EP reached 29.90 mm and 23.36 respectively, and the expansion of char layer was more uniform. This indicates that the addition of LST hybrid material can improve the mechanical strength of char layer and attenuate the heat transfer rate in the vertical direction. The residual char of LST/EP was 33.2% by thermogravimetric analysis, indicating that the addition of LST could reduce the volatilization of volatile components and improve the thermal stability of EP.

Inhibition effect and mechanism of nano-aluminum hydroxide foam on coal spontaneous combustion

The inhibition performances of nano-aluminum hydroxide (nano-ATH) foam were evaluated by thermal gravimetric analyzer and cone calorimeter. Results demonstrate that the dry cracking temperature point and ignition temperature point of coal samples increase after nano-ATH foam processing, while the percentage of weight loss decreases. In particular, the dry cracking temperature point increases form 93.2 °C to 164.6 °C, the ignition temperature point increases from 406.9 °C to 443.6 °C, and the weight loss percentage decreases from 34% to 20%. According to the combustion experiment, the peak heat release rate of the coal samples processed by nano-ATH foam decrease from 123.36 kW/m2 of the raw coal to 49.849 kW/m2. Meanwhile, the peak smoke release rate, and the total smoke releasing volume decrease from 0.093 m2/s to 0.006 m2/s, and from 1.027 m2 to 0.574 m2, respectively. Finally, infrared spectral analysis of the coal samples was carried out to investigate variations in functional groups in coals under different characteristic temperatures.

A green and facile strategy to enhance thermal stability and flame retardancy of unidirectional flax fabric based on fully bio-based system

Although layer-by-layer (LBL) self-assembly technology played a wide range of applications in the field of flame-retardant profiting from the advantages of various ingredient combinations, working on a variety of substrates and ambient processing, it required repeated assembly to achieve the desired flame retardancy, which increased the time-cost and complexity of the process, restricting further application. In this work, fully bio-based flame-retardant system based on phytic acid (PA) and ammonium alginate (AA) was designed, which endowed flax fabric with excellent flame retardancy with only the assembled layers of 1 biolayer. Compared with pristine flax fabric, the limiting oxygen index (LOI) of Flax-AA/PA reached 32.2% (∼68.6% increase), and revealed faster self-extinguishing behavior. Moreover, the peak heat release rate (PHRR), total heat release (THR), peak smoke release rate (PSPR) and total smoke release (TSR) were decreased by 65.1%, 52.7%, 64.4% and 32.1%, respectively. Both the number of assembled layers and the flame-retardant effect were superior to the previously reported systems through LBL self-assembly technology. Mechanism analysis illustrated that the AA/PA flame-retardant system reduced the production of flammable volatiles (carbonyl compounds, aromatic compounds, hydrocarbons, etc), and promoted the dehydration of flax fabric to form phosphorus-containing hybrid char layer which inhibited the heat and mass transfer between the pyrolysis zone and the combustion zone, thus delaying the spread of combustion. This bio-based flame-retardant system provides a facile LBL self-assembly at an ultra-low number of assembled layers to endow the unidirectional flax fabric with excellent flame retardancy.