High-Efficiency Flame Retardants of a P-N-Rich Polyphosphazene Elastomer Nanocoating on Cotton Fabric

Green fabrication of highly flame-retardant, anti-ultraviolet radiation and superhydrophobiccellulose-based fabric by constructing dualtielement-containing NH2-MIL-53(Al)@Triethoxyoctylsilane nano coatings

The facile and eco-friendly fabrication of a fabric with remarkable flame retardancy, anti-ultraviolet (UV), and superhydrophobic properties is of significant interest for multitask requirements. In this regard, herein, a nonfluorine, facile, and green method is reported for in situ synthesis of metal-organic frame (NH2-MIL-53(Al)) on hemp fabric (HF) for the preparation of multifunctional textiles. A homogeneous and compact coating of NH2-MIL-53(Al) crystals was deposited on HF, followed by modification with triethoxyoctylsilane (TEOS) to manufacture superhydrophobic NH2-MIL-53(Al)@hemp fabric (SM(Al)HF-9), significantly enhancing its water stability. The SM(Al)HF-9 exhibited superior superhydrophobicity properties, with a water contact angle (WCA) up to 156°. Furthermore, the surface of SM(Al)HF-9 cannot be adhered by dye solution and powder, indicating its good self-cleaning and anti-fouling abilities. The SM(Al)HF-9, characterized by a porous structure, effectively separates tetrachloromethane and n-hexane from water mixtures with a separation efficiency exceeding 97 %. The SM(Al)HF-9 has excellent UV-blocking properties, and the UV protection factor is as high as 105.44. Encouragingly, the SM(Al)HF-9 exhibited outstanding flame retardancy, as demonstrated by its self-extinguishing capability and a substantially improved limiting oxygen index (LOI) of 32.4 %. In comparison to raw HF, the peak heat release rate (PHRR) and total heat rate (THR) of the modified HF are reduced by 76.15 % and 54.32 %, respectively. Meanwhile, the NH2-MIL-53(Al) has a significant advantage over other MOFs (e.g., ZIF-67, Ce-MOF, Ag-MOF, Fe-MOF and MIL-53(Al)) in improving the flame retardancy of HF. The highly efficient flame-retardant, anti-UV, and superhydrophobic fabric is promising in home and public decoration, and fire protection fields.

A halogen-free flame retardant with P/N and optimization for cotton fabrics tensile properties

Cotton fibers' flammability and rapid combustion greatly restrict their usage in industries that require higher flame retardancy. Phosphorus and nitrogen-based flame retardants are frequently employed in the textile industry to consolidate the flame resistance of cotton materials. To consolidate flame retardant performance, a novel flame retardant named HPAPU was synthesized by combining 3-hydroxyphenylphosphinylpropionic acid, 1,6-hexanediamine, phosphoric acid, and urea. The structure of the products at each step was analyzed using Fourier transform infrared spectroscopy. In addition, the NMR was utilized to confirm that it was successfully synthesized. In order to evaluate the flame retardancy of HPAPU-treated cotton fabrics, the limiting oxygen index (LOI) was measured. The results showed that the LOI of the cotton fabric with 27.5 % weight gain was 38.5 %, which is a significant increase compared to the pure cotton fabric. According to the cone calorimeter test, the HPAPU-treated cotton fabrics showed a decrease in 86.6 % in peak heat release rate and 41.67 % in peak total heat release rate compared with unprocessed samples. In the tensile test, we found that increasing the flame-retardant concentration can improve the fabrics' tensile strength.

Study on Flame Retardancy of Cotton Fabric Modified by Sulfonic Groups Chelated with Ba2

A simple and innovative method was introduced for the production of green and recoverable flame-retardant cotton fabrics, where sulfonated cotton fabric (COT-SC) was synthesized by oxidizing cotton fabric with sodium periodate, followed by a sulfonation step with sodium bisulfite to provide active sites, which further chelated barium ions (Ba2+) to achieve flame retardancy. The morphological and structural characterizations of the fabricated cotton fabrics (COT-SC-Ba) demonstrated that the cleavage of C2-C3 free hydroxy groups within the cellulose macromolecule was chemically modified for grafting a considerable number of sulfonic acid groups, and Ba2+ ions were effectively immobilized on the macromolecule of the cotton fabric through a chelation effect. Results from cone calorimeter tests (CCTs) revealed that COT-SC-Ba became nonflammable, displayed a delayed ignition time, and decreased the values of the heat release rate (HRR), total smoke release (TSR), effective heat of combustion (EHC), and CO/CO2 ratio. TG/DTG analysis demonstrated that COT-SC-Ba possessed greater thermal stability, fewer flammable volatiles, and more of a char layer during burning than that of the original cotton fabric. Its residual mass was increased from 0.02% to 26.9% in air and from 8.05% to 26.76% in N2, respectively. The COT-SC-Ba not only possessed a limiting oxygen index (LOI) of up to 34.4% but could also undergo vertical burning tests evidenced by results such as the non-afterflame, non-afterglow, and a mere 75 mm char length. Those results demonstrated that the combination of SO3- and Ba2+ promoted the formation of a char layer. Moreover, cotton fabric regained its superior flame retardancy after being washed and re-chelated with Ba2+. Additional characteristics of the cotton fabric, such as the rupture strength, white degree, and hygroscopicity, were maintained at an acceptable level. In conclusion, this research can offer a fresh perspective on the design and development of straightforward, efficient, eco-friendly, and recoverable fire-retardant fabrics.

Synthesis of a novel Si-N-S flame retardant and its application on cotton cellulose biomacromolecule

A novel flame retardant containing Si, N, and S elements, ((2-(triethoxysilyl)ethyl)thio)ethan-1-amine hydrochloride (TETEA), was synthesized via a click reaction and characterized using nuclear magnetic resonance spectroscopy (NMR) and fourier transform infrared spectroscopy (FTIR). Subsequently, the flame-retardant cotton fabric was fabricated by sol-gel method. The results indicated that TETEA was successfully loaded on cotton fabric and formed a uniform protective layer on the surface of cotton fabric, exhibiting excellent flame retardancy. The flame-retardant cotton fabric achieved limiting oxygen index (LOI) of 28.3 % and passed vertical combustion test without after-flame or afterglow time at TETEA concentration of 500 g/L. Thermogravimetric analysis revealed that the residual carbon content of the flame-retardant cotton fabric was much higher than that of the control under air and N2 conditions. Besides, the flame-retardant cotton fabric was not ignited in cone calorimeter test with an external heat flux of 35 kW/m2. The peak heat release rate and the total heat release decreased from 133.4 kW/m2 to 25.8 kW/m2 and from 26.46 MJ/m2 to 17.96 MJ/m2, respectively. This phosphorus-free flame retardant offers a simplified synthesis process without adverse environmental impacts, opening up a new avenue for the development environmentally friendly flame retardants compared to traditional alternatives.

Construction of efficient and environmentally friendly bio-based flame retardant cotton fabric through layer by layer self-assembly of alkylammonium functional silsesquioxane/phosphorylated sodium alginate

As an important source of green cleaning flame retardants, bio-based materials have been widely studied by researchers. However, the development of efficient biobased flame retardants and convenient finishing methods was of great significance for the functional finishing of materials. Herein, a convenient and efficient flame retardant cotton fabric was prepared via layer by layer self-assembly (LbL) by alternating precipitation of a novel bio-based flame retardant phosphorylated sodium alginate (PSA) and alkylammonium functionalized siloxane (A-POSS). The effect of coating number on flame retardancy and thermal properties of coated cotton fabric was systematically studied. Thermogravimetric analysis (TGA) results showed that residual char contents of AP/PS-15BL under air and N2 atmospheres increased by 252.0% and 225.2%, respectively, compared with control cotton. In vertical flammability tests, both the AP/PS-10BL and AP/PS-15BL showed self-extinguishing behavior and successfully passed the UL-94 V-0 rating. More importantly, the LOI value of AP/PS-15BL was significantly increased to 35.0% from 20.0% of pure cotton fabric. Additionally, coated samples showed good mechanical properties and washable resistance. In CONE test, the peak heat release rate (PHRR) and total heat release rate (THR) of AP/PS-15BL decreased by 89.3% and 49.3% respectively, compared with control cotton. Therefore, this green and convenient flame-retardant finishing method has great application potential in the multi-functional finishing of cotton fabrics.

Biomimetic Nanoporous Transparent Universal Fire-Resistant Coatings

The inherent flammability of most polymeric materials poses a significant fire hazard, leading to substantial property damage and loss of life. A universal flame-retardant protective coating is considered as a promising strategy to mitigate such risks; however, simultaneously achieving high transparency of the coatings remains a great challenge. Here, inspired by the moth eye effect, we designed a nanoporous structure into a protective coating that leverages a hydrophilic-hydrophobic interactive assembly facilitated by phosphoric acid protonated amino siloxane. The coating demonstrates robust adhesion to a diverse range of substrates, including but not limited to fabrics, foams, paper, and wood. As expected, its moth-eye-inspired nanoporous structure conferred a high visible light transparency of >97% and water vapor transmittance of 96%. The synergistic effect among phosphorus (P), nitrogen (N), and silicon (Si) largely enhanced the char-forming ability and restricted the decomposition of the coated substrates, which successfully endowed the coating with high fire-fighting performance. More importantly, for both flexible and rigid substrates, the coated samples all possessed great mechanical properties. This work provides a new insight for the design of protective coatings, particularly focusing on achieving high transparency.

Evaluating the fire resistance and durability of cotton textiles treated with a phosphoramide phosphorus ester phosphate ammonium flame retardant

The phosphoramide phosphorus ester phosphate ammonium (PPEPA) flame retardant was synthesized by phosphorus oxychloride and ethanolamine, and its structure was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy (FTIR). Cotton textiles treated with 20 wt% PPEPA (CT-PPEPA3) would have high durability and flame retardance. The limiting oxygen index (LOI) of CT-PPEPA3 was found to be 46.5 %, while after undergoing 50 laundering cycles (LCs) following the AATCC 61-2013 3 A standard, the LOI only decreased to 31.4 %. Scanning electron microscopy and X-ray diffraction analyses suggested the penetration of PPEPA molecules into the interior of cotton fibers, resulting in a minor alteration of the cellulose crystal structure. The excellent durability, FTIR, and energy-dispersive X-ray of CT-PPEPA3 provided evidence for the formation of -N-P(=O)-O-C- and -O-P(=O)-O-C- covalent bonds between the PPEPA molecules and cellulose. The -N-P(=O)-O-C- bond exhibited a p-π conjugation effect, leading to enhanced stability and improved durability of the flame-retardant cotton textiles. Vertical flame, thermogravimetric, and cone calorimetry tests demonstrated that the CT-PPEPA3 underwent condensed-phase and synergistic flame retardation. Additionally, these finished cotton textiles retained adequate breaking strength and softness, making them suitable for various applications. In conclusion, the incorporation of the -N-P(=O)-ONH4 group into the phosphorus ester phosphate ammonium flame retardant demonstrated effective enhancement of the fire resistance and durability of treated cotton textiles.

Phosphamide-Based Washing-Durable Flame Retardant for Cotton Fabrics

A formaldehyde-free reactive flame retardant, an ammonium salt of triethylenetetramine phosphoryl dimethyl ester phosphamide phosphoric acid (ATPEPDPA), was synthesized and characterized using nuclear magnetic resonance (NMR). Fourier transform infrared spectroscopy test (FT-IR), durability test and scanning electron microscopy (SEM) results suggested that ATPEPDPA was successfully grafted on cotton fabrics through a -N-P(=O)-O-C covalent bond. Moreover, the limiting oxygen index (LOI) value of 20 wt% ATPEPDPA-treated cotton was 44.6%, which met stringent washing standard after 50 laundering cycles (LCs). The high washing resistance of the ATPEPDPA-treated cotton was due to the p-π conjugation between the N atom and the P(=O) group in the flame-retardant molecule, which strengthened the stability of the -N-P(=O)-O-C bonds between ATPEPDPA and cellulose, and the -N-P(=O)-(O-CH3)2 groups in the ATPEPDPA. The cone calorimetric test showed that the treated cotton had excellent flame retardance. In addition, the TG and TG-IR tests suggested that ATPEPDPA performed a condensed flame retardance mechanism. Furthermore, the physical properties and hand feel of the treated cotton were well maintained. These results suggested that introducing -N-P(=O)-(O-CH3)2 and -N-P(=O)-(ONH4)2 groups into ATPEPDPA could significantly increase the fire resistance and durability of cotton fabrics.

Enhanced safety and strength of cotton fabrics through a novel 'H-shaped' multiple flame retardant elements agent

In response to the new concept of green sustainability, it is necessary to expand the functionality of bio-based natural fibers (such as cotton fabrics) to replace fabrics made from fossil fuels. One potential way of achieving this is through the use of phosphorus, boron and nitrogen based organic flame retardants. This article designs a special flame retardant system with high efficiency, high durability, and enhanced fabric strength. An "H" shaped flame retardant (TBSA) is synthesized using hydroxyethyl methylene phosphate, pentaerythritol diborate, and cyanuric chloride. After simple treatment, flame retardant fabric (TBSA/Cotton) is obtained, with a LOI value of 48.8 %. Self extinguishing is completing in the vertical flame test. The high FR efficiency reflects the progressiveness of multi flame retardant elements. It is worth noting that TBSA/Cotton exhibits excellent durability and improves the strength of the fabric. This is attributed to the covalent bonding between the "H" type flame retardant and multiple cellulose molecules, which compensates for the cracks and holes at the submicroscopic scale of natural cellulose and weakens the molecular slip effect. The research results of this article provide a good opportunity for the development of biomass cellulose flame retardant materials.

Two birds, one stone: Enhancement of flame retardancy and antibacterial property of viscose fabric using an aminoazole-based cyclotriphosphazene

Enhancing the fire-retardant and antibacterial properties of viscose fabric through a simple strategy is crucial and urgent. In this study, an aminoazole-based cyclotriphosphazene (HATA) was designed and synthesized through nucleophilic substitution between hexachlorocyclotriphosphazene and 3-amino-1,2,4-triazole. The application of a rapid dipping strategy and the use of 10 wt% HATA aqueous solution significantly increased the limiting oxygen index of the viscose fabric from 19.3 % to 28.4 %. In addition, the HATA-treated fabric exhibited self-extinguishing properties in vertical flame testing. The peak heat release rate of HATA-treated fabric, according to pyrolysis combustion flow calorimetry, significantly decreased by over 83 %. The scanning electron microscope images revealed the original woven fabric structure after burning. The thermogravimetric infrared spectroscopy and X-ray photoelectron spectroscopy results confirmed that the introduction HATA in viscose hindered the release of combustible gas and facilitated the formation of a protective char layer. In addition, 10 % HATA-viscose exhibited remarkable antimicrobial properties, achieving 99.96 % and 99.84 % antibacterial rates against Staphylococcus aureus and Escherichia coli, respectively. Furthermore, HATA-treated viscose fabric exhibited favorable mechanical performance, whiteness, and air permeability. This research provides a simple and effective flame-retardant and antibacterial treatment strategy for viscose fabric.

Surface Flame-Retardant Systems of Rigid Polyurethane Foams: An Overview

Rigid polyurethane foam (RPUF) is one of the best thermal insulation materials available, but its flammability makes it a potential fire hazard. Due to its porous nature, the large specific surface area is the key factor for easy ignition and rapid fires spread when exposed to heat sources. The burning process of RPUF mainly takes place on the surface. Therefore, if a flame-retardant coating can be formed on the surface of RPUF, it can effectively reduce or stop the flame propagation on the surface of RPUF, further improving the fire safety. Compared with the bulk flame retardant of RPUF, the flame-retardant coating on its surface has a higher efficiency in improving fire safety. This paper aims to review the preparations, properties, and working mechanisms of RPUF surface flame-retardant systems. Flame-retardant coatings are divided into non-intumescent flame-retardant coatings (NIFRCs) and intumescent flame-retardant coatings (IFRCs), depending on whether the flame-retardant coating expands when heated. After discussion, the development trends for surface flame-retardant systems are considered to be high-performance, biological, biomimetic, multifunctional flame-retardant coatings.

Nonaqueous Interfacial Polymerization-Derived Polyphosphazene Films for Sieving or Blocking Hydrogen Gas

A series of cyclomatrix polyphosphazene films have been prepared by nonaqueous interfacial polymerization (IP) of small aromatic hydroxyl compounds in a potassium hydroxide dimethylsulfoxide solution and hexachlorocyclotriphosphazene in cyclohexane on top of ceramic supports. Via the amount of dissolved potassium hydroxide, the extent of deprotonation of the aromatic hydroxyl compounds can be changed, in turn affecting the molecular structure and permselective properties of the thin polymer networks ranging from hydrogen/oxygen barriers to membranes with persisting hydrogen permselectivities at high temperatures. Barrier films are obtained with a high potassium hydroxide concentration, revealing permeabilities as low as 9.4 × 10^-17 cm³ cm cm^-2 s^-1 Pa^-1 for hydrogen and 1.1 × 10^-16 cm³ cm cm^-2 s^-1 Pa^-1 for oxygen. For films obtained with a lower concentration of potassium hydroxide, single gas permeation experiments reveal a molecular sieving behavior, with a hydrogen permeance of around 10^-8 mol m^-2 s^-1 Pa^-1 and permselectivities of H₂/N₂ (52.8), H₂/CH₄ (100), and H₂/CO₂ (10.1) at 200 °C.

Flame retardant cotton fabrics with anti-UV properties based on tea polyphenol-melamine-phenylphosphonic acid

A novel, high-efficiency, phosphorus-nitrogen flame retardant based on tea polyphenol-melamine-phenylphosphonic acid (named TP-MA-PPOA) for cotton fabrics was prepared successfully. TP-MA-PPOA coating gives the cotton fabrics flame retardancy and anti-UV properties. The results reveal that the TP-MA-PPOA coating enables cotton fabrics to self-extinguish, the damage length is only 7.4 cm in vertical flame test, and the limiting oxygen index increases to 28.7%. Meanwhile, Cotton/TP-MA-PPOA also performs well in cone calorimetry test, as evidenced by 88.5% reduction of peak heat release rate, and 92.9% decrease of the fire growth rate compared with that of cotton fabrics. And the risk of fire is sharply reduced. In addition, the ultraviolet protection factor value of Cotton/TP-MA-PPOA is 35.2. Encouragingly, the TP-MA-PPOA coating shows little deterioration in the handle of the cotton fabrics.

Fabrication of Highly Efficient Flame-Retardant and Fluorine-Free Superhydrophobic Cotton Fabric by Constructing Multielement-Containing POSS@ZIF-67@PDMS Micro-Nano Hierarchical Coatings

The facile construction of a cotton fabric with excellent flame-retardant and water-proof abilities is of great interest for multitask requirements. Herein, a nonfluorine, highly efficient, and cost-effective multifunctional cotton fabric was fabricated via sequentially depositing a novel multielement-containing flame-retardant phosphorylated octa-aminopropyl POSS (PPA-POSS) and a fluorine-free superhydrophobic coating of zeolitic imidazolate framework-67@poly(dimethylsiloxane) (ZIF-67@PDMS). Influences of the PPA-POSS concentration and ZIF-67@PDMS formula on the fire retardancy and water repellency of treated cotton were systematically investigated. The optimized flame-retardant sample CTF3 with 6.2 wt % PPA-POSS exhibited a high limiting oxygen index (LOI) of 34% and self-extinguishing ability. CTF3 was further modified with a properly formulated superhydrophobic ZIF-67@PDMS coating. CTF3-PHB2 displayed enhanced thermal stability, flame retardancy, and outstanding superhydrophobicity. Thermogravimetric analysis (TGA) results demonstrated that CTF3-PHB2 presented a high char residue of 35.9%, which was 220.5% higher than that of the control cotton (11.2%). More importantly, the heat release rate (HRR), total heat release (THR), and average effective heat of combustion (av-EHC) values of CTF3-PHB2 were significantly reduced by 51.4, 56.2, and 68.4%, respectively, compared with those of a pure cotton fabric. Moreover, CTF3-PHB2 showed superhydrophobicity (WCA > 159.3°) and good mechanical abrasion resistance. In addition, CTF3-PHB2 also showed protective abilities such as antifouling, self-cleaning, and water/oil separation performances even for strong acid/alkali mixtures. Thereby, it is believed that the PPA-POSS@ZIF-67@PDMS coating is promising for application in multifunctional textile materials.

Fire retardant polyethylene terephthalate containing 4,4′-(hexafluoroisopropylidene)diphenol-substituted cyclotriphosphazene microspheres

Polyphosphazene derivatives are gaining popularity due to their eco-friendly character and high content of flame-retardant components. Herein, a polyphosphazene derivative (PZAF) microsphere was successfully synthesized utilizing an in-situ template approach, which was then employed as an additive flame retardant in polyethylene terephthalate (PET) to improve the fire safety. Thermogravimetric analysis revealed that PZAF promoted the pyrolysis of PET in advance to generate a stable char layer that protects the matrix from heat, consequently increasing char residues. With addition of 10 wt% PZAF, the PET nanocomposites obtained a V-0 grade in vertical combustion test and its LOI value increased from 24.2 vol% to 32.1 vol%. Moreover, the peak heat release and carbon monoxide production decreased by 46.6% and 50.6%, respectively. This was because the phosphonic acid fragments and pyridine ring compounds produced by the PZAF pyrolysis encouraged the development of a robust char layer. Meanwhile, the •PO radicals generated by the pyrolysis of PZAF could capture free radicals in the gas phase, ultimately ending the chain reaction of combustion. Also, mechanical properties of the PET nanocomposites were noticeably enhanced by the addition of 3 or 5 wt% PZAF.

Chitosan/sodium polyborate based micro-nano coating with high flame retardancy and superhydrophobicity for cotton fabric

In this work, a sustainable flame retardant and superhydrophobic cotton fabric was prepared by a two-step process: the cotton fabric was firstly treated with a chitosan/sodium polyborate polyelectrolyte complex water solution to obtain a flame retardant layer, and then treated with a polydimethylsiloxane (PDMS) tetrahydrofuran solution to construct a superhydrophobic layer. The phase-separated chitosan with a micro-nano roughness structure was covered by PDMS, which synergistically improved the hydrophobicity of the cotton fabric. The flammability evaluation indicated that the limiting oxygen index value of the treated fabric was increased to 40.0% from 18.2%, the peak of heat release rate was reduced by 63.8%, and the total heat release was reduced by 57.6% compared with that of the control sample. The enhanced flame retardancy was attributed to the excellent charring ability in the condensed phase. The treated fabric also showed anti-sticking, self-cleaning, and oil/water-separating properties. This coating treatment without any F, Cl, Br, P elements involved is regarded as a clean methodology for producing flame retardant and superhydrophobic cotton fabrics.