Vertical Flame Test Research Articles

Durable flame retardant hybrid sol–gel coating on poly(ethylene terephthalate) fabric and its flame retardant mechanism

In this paper, an organic/inorganic phosphorus and silicon-containing coating was prepared by the sol–gel method and its flame retardant mechanism for poly(ethylene terephthalate) (PET) fabrics was thoroughly investigated. The influence of hybrid coating on PET fabric was investigated by the limited oxygen index (LOI), vertical flammability test (VFT) and microscale combustion calorimetry (MCC). The results revealed that the LOI of the coated PET fabric was up to 29.2% and no dripping was observed in the VFT. MCC results showed that hybrid coating reduced the peak heat release rate, heat release capacity and total heat release of PET fabric. Thermogravimetric analysis demonstrated increased thermal stability and char residue of PET fabrics due to the hybrid coating. Furthermore, the char residues were studied by X-ray photoelectron spectroscopy and scanning electron microscopy. The above results proved that the synergistic effect between the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide group and the silicon network played a key role in the flame retardancy of PET fabrics. In addition, the durability of coated PET fabrics was interpreted by calculating the interaction energy through molecular dynamics simulation.

An eco-friendly N[sbnd]P flame retardant for durable flame-retardant treatment of cotton fabric

A halogen-free, formaldehyde-free, efficient, durable, NP flame retardant, the ammonium salt of meglumine phosphoric ester acid (ASMPEA), was prepared. The Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR, and 31P NMR) results indicated that ASMPEA was grafted onto cotton fibers by P-O-C covalent bonds. The LOI value of 30 wt% ASMPEA-treated cotton fabric was 40.2%, and after 50 laundering cycles (LCs), the LOI value decreased to 29.4%, indicating that the cotton fibers treated with ASMPEA were endowed with excellent durable flame retardancy. Thermogravimetry (TG), cone calorimetry, and vertical flammability test results showed that ASMPEA-treated cotton decomposed into phosphoric acid or polyphosphoric acid during combustion, which promoted the thermal degradation and charring of treated cotton fabrics and hindered the spread of flames. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectrometry (EDS) verified that ASMPEA infiltrated the cotton fiber without obviously affecting its surface morphology or crystal structure; however, the mechanical properties of the treated cotton fabric decreased slightly. These results confirm that ASMPEA achieved excellent durable flame retardancy when used to coat cotton fabric.

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

Modification by intumescent flame retardants is an effective way to impart antiflame properties to fabric materials. Polyphosphazene elastomers contain all three elements required by intumescent flame retardants: an acid source, a gas source, and a carbon source, making them all-in-one integrated intumescent flame retardants. In this work, halogen-free poly(dimethoxy)phosphazene (PDMP) loaded with 29.0 wt % phosphorus and 13.1 wt % nitrogen is shown to be an ideal flame retardant for fabric materials. For the first time, transparent and elastic PDMP was applied as an intumescent flame retardant for cotton fabric. The PDMP-coated cotton shows remarkable high-efficiency flame-retardant properties: (1) a self-extinguishing property during the vertical flame test is obtained when the add-on level reaches 5.3 wt %, with a lower smoke release character; (2) the limiting oxygen index (LOI) values of coated cotton are improved with increasing add-on level, and the thickness of the coating is measured to be at the nanolevel, 2540 nm when 10.9 wt % PDMP is coated. The coated cotton shows enhanced carbonization ability at lower temperatures, which is the key to imparting flame-retardant properties to cotton, and the PDMP-coated cotton shows remarkably lower peak heat release rate and total heat release compared to the control cotton during combustion. The durability of modified cotton was tested after 50 laundering cycles, which showed that the coating maintains 80% of its initial mass, and the after-laundering sample preserves the characteristics of self-extinguishing and a high LOI. Thus, the PDMP nanocoating-modified flame-retardant cotton fabric is sufficiently durable for practical application.

Eco-friendly coating based on an intumescent flame-retardant system for viscose fabrics with multi-function properties: Flame retardancy, smoke suppression, and antibacterial properties

Ammonium phytate and chitosan were chosen as eco-friendly flame retardants to improve the flame retardancy and antibacterial properties of viscose fabrics. The flame-retardant viscose fabrics exhibited sharp improvements in thermal stability at the higher temperature zone, and 2BLviscose retained 39.0% char residues at 700 °C. 2BL/viscose obtained a limiting oxygen index value of 29% and self-extinguished in the vertical flame test. The fire behaviors of the flame-retardant viscose fabrics were also enhanced; even the addition of CS decreased the total smoke production value from 0.6 to 0.3 m2. Flame-retardant viscose fabrics released less flammable substances and more H2O, resulting in combustion choking. Meanwhile, the flame-retardant samples formed stable char residues, which were mainly constituted by graphite. Meanwhile, the viscose fabrics coated with CS/AP exhibited excellent antimicrobial properties, and 2BL/viscose obtained a 99.99% antibacterial rate for both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).

Synergistic Flame Retardant Effects of Carbon Nanotube‐Based Multilayer Nanocoatings

AbstractIn an effort to develop highly functionalized flame retardant materials, hybrid nanocoatings are prepared by alternately depositing a positively charged polyaniline (PANi) and negatively charged montmorillonite (MMT) using the layer‐by‐layer (LbL) assembly technique. Carbon nanotubes (CNTs) are employed in polymer nanocomposites as effective reinforcement, where nanotubes are stabilized in MMT aqueous solution. The 3D structure and high density of CNTs deposited in the PANi/CNTs‐MMT multilayers produce thicker and heavier coatings in comparison to the LbL assemblies without CNTs. Vertical and horizontal flame testing show that the incorporation of CNTs improves fire resistance. Additionally, cone calorimetry reveals that stacking two nanomaterials (MMT and CNTs) in a single coating shows a significant reduction in peak heat release rate (up to 51%), total smoke release (up to 47%), and total heat release (up to 37%) for the polyurethane foam. The enhancement of flame retardancy is attributed to a synergistic effect; MMT serves as a physical barrier that retards the diffusion of heat and gas. The addition of CNTs strengthens the thermal stability and high char yield. These results, coupled with the simplicity with which the LbL deposition is applied, present a viable alternative to halogen‐free flame retardant nanocoatings to natural and synthetic fibers.

A novel aminothiazole-based cyclotriphosphazene derivate towards epoxy resins for high flame retardancy and smoke suppression

There is a need to develop halogen-free flame retardants for epoxy resin (EP) to reduce the fire risks. Cyclotriphosphazene-based derivatives have been proved to be effective phosphorous-containing flame retardants. This article demonstrates the preparation and application of a novel aminothiazole-based cyclotriphosphazene derivate (hexathiazoleaminocyclotriphosphazene, HTACP) for EP. After characterizing by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance, and high-resolution mass spectroscopy, HTACP is utilized as a reactive flame retardant for EP. HTACP effectively inhibits the decomposition of EP and improves the char yield during heating according to the thermogravimetric analysis (TGA) results. HTACP also changes the dynamic thermomechanical behaviors of EP according to dynamic mechanical analysis (DMA). With the incorporation of 5 wt% HTACP, EP passes UL-94 V-0 rating during the vertical flame testing and obtains an increased limiting oxygen index of 28.5% with only 0.73% phosphorous content. The cone calorimeter testing results show that HTACP endows EP with beyond 50% reduction of peak heat release rate and total smoke production. The results of smoke density chamber tests also prove the excellent smoke-suppression effects for EP. Furthermore, scanning electron micrograph, X-ray photoelectron spectroscopy, TG-FTIR, and pyrolysis gas chromatography/mass spectrometry are used to analyze the chars and pyrolysis behaviors of EP/HTACP. The phosphazene structure in HTACP molecule is left in the condensed phase, which promotes forming protective chars, while the multiple nitrogen- and sulfur-containing volatiles derives from aminothiazole groups act dilution effects in the flame zone. This novel aminothiazole-based cyclotriphosphazene shows a high efficiency for reducing fire hazards of EP through a bi-phase mechanism.

Sodium Lignin Sulfonate (SLS) and Pomegranate Rind Extracts (PRE) Bio-macro-molecule: A Novel Composition for Making Fire Resistant Cellulose Polymer

ABSTRACT A novel formulation of the sodium lignin sulfonate (SLS) [bio based branched chain lignin polymer modified with the sulfonic acid] and the pomegranate rind extract (PRE), a wastage plant biomolecule, has been applied to the cellulosic cotton fabric to make it flame retardant. It was found that the control, 10% SLS and the PRE treated cotton fabric showed the limiting oxygen index (LOI) value of 18, 25, and 24, respectively and completely burnt within one to two minutes in the vertical flammability test. On the contrary, (PRE+ 10% SLS) treated cotton fabric showed 32% add-on and the LOI value of 32 with the specific char length of 40 mm after the completion of the vertical flammability test as per IS1871 method A. Extent of the afterglow duration and the char length, both have been decreased with increasing the percentage concentration of the SLS [5 to 10% (W/V)] into the PRE mixture. Thermo-gravimetry (TG) analysis of the control, PRE and the 10% SLS treated cotton fabric showed only 10% remaining char mass at 450°C in air atmosphere whereas the (PRE+ 10% SLS) treated fabric showed much lower mass loss rate and 45% remaining char mass at the said temperature. Moreover, the char morphology of the (PRE+ 10% SLS) formulation treated fabric showed structural integrity (weave of the fabric) with the presence of the small bubbles after the completion of the combustion phenomena. Mechanism of the fire retardancy revealed the fact that during the treatment, nitrogen containing alkaloids, long chain carbon molecule, poly phenolic compounds (present in the PRE) and the sulfur containing sulfonate groups, polyphenolic compounds (present in the SLS) deposited on the cotton fabric surface, combinedly acted on the flame retardancy (to arrest the both flame and the afterglow) and the char formation of the underlying cellulose structure, during burning. Moreover, the detail color values of the control and the treated fabrics also have been elucidated in the present research context.

Preparation and mechanism of phosphoramidate-based sol-gel coating for flame-retardant viscose fabric

To prepare efficiently flame-retardant sol-gel coating for viscose fabric, a novel phosphoramidate siloxane (TSPDP) was synthesized and fire-safety viscose fabrics were prepared via sol-gel method with different contents of TSPDP. When the weight gain (WG) was more than 13%, higher limiting oxygen index (LOI) value was obtained and the coated viscose fabric passed the vertical flammability test with self-extinguishing behavior. A sharp reduction of more than 42% in peak of heat release rate (pHRR) was discovered for coated viscose fabric in contrast with pure sample. The good flame retardancy of TSPDP-coated viscose fabric was due to the co-presence of P, N and Si elements, which can form a char layer barrier in condensed phase during the combustion and inhibit the release of flammable volatiles in high temperature. Moreover, this coating had few effects on the tensile strength of viscose fabric.

Bioinspired Adenosine Triphosphate as an "All-In-One" Green Flame Retardant via Extremely Intumescent Char Formation.

The development of eco-friendly flame retardants is crucial due to the hazardous properties of most conventional flame retardants. Herein, adenosine triphosphate (ATP) is reported to be a highly efficient "all-in-one" green flame retardant as it consists of three essential groups, which lead to the formation of char with extreme intumescence, namely, three phosphate groups, providing an acid source; one ribose sugar, working as a char source; and one adenine, acting as a blowing agent. Polyurethane foam was used as a model flammable material to demonstrate the exceptional flame retardancy of ATP. The direct flammability tests have clearly shown that the ATP-coated polyurethane (PU) foam almost did not burn upon exposure to the torch flame. Importantly, ATP exhibits an extreme volume increase, whereas general phosphorus-based flame retardants show a negligible increase in volume. The PU foam coated with 30 wt % of ATP (PU-ATP 30 wt %) exhibits a significant reduction in the peak heat release rate (94.3%) with a significant increase in the ignition time, compared to bare PU. In addition, PU-ATP 30 wt % exhibits a high limiting oxygen index (LOI) value of 31% and HF-1 rating in the UL94 horizontal burning foamed material test. Additionally, we demonstrated that ATP's flame retardancy is sufficient for other types of matrices such as cotton, as confirmed from the results of the standardized ASTM D6413 test; cotton-ATP 30 wt % exhibits an LOI value of 32% and passes the vertical flame test. These results strongly suggest that ATP has great potential to be used as an "all-in-one" green flame retardant.

Fabrication of multifunctional PET fabrics with flame retardant, antibacterial and superhydrophobic properties

The multifunctional polyethylene terephthalate (PET) fabrics with flame retardant, antibacterial and superhydrophobic properties were successfully fabricated by a simple coating approach to enhance the properties of PET fabrics and to make them extensively applicable in a number of fields. The composite coating was composed of ammonium polyphosphate (APP), polydopamine (PDA), PDMS-silica (PDMS-SiO2), and silver nanoparticles (AgNPs). ATR-FTIR spectra, XPS analysis, and SEM-EDS spectrometer were employed to investigate the morphological properties and constitution of these coatings. The flame retardant performance of the multifunctional PET fabrics was determined by LOI, vertical flame test (VFT) and cone calorimeter test (CCT). The results revealed that the APP@SiO2-PDA@Ag PET fabrics' LOI value reached 29.0 %, which was 9.5 % higher than that of pristine PET fabrics. Besides, the APP@SiO2-PDA@Ag PET fabrics could self-extinguish the fire quickly in the VFT. The peak heat release rate and total heat release of the APP@SiO2-PDA@Ag PET fabrics were 34 % and 26 % lower than those of the pristine one. Notably, the multifunctional PET fabrics had excellent antibacterial activity against E. coli and S. aureus. The multifunctional fabrics exhibited superhydrophobicity with a water contact angle (CA) greater than 150° and showed excellent self-cleaning and antifouling properties. More importantly, the multifunctional PET fabrics still retained excellent flame retardant performance and antibacterial properties after multiple washing cycles.

Environmentally-benign, water-based covalent polymer network for flame retardant cotton

Relatively simple flame retardant finishing technologies for cotton are greatly desired in a variety of fire-sensitive applications (e.g., transportation, workwear, etc.). Many current industrial processes take advantage of halogen-containing flame retardants or require complicated processing. This study demonstrates a simple and halogen-free flame retardant treatment for cotton, which proceeds via a spontaneous Mannich-type reaction between branched polyethylenimine (PEI) and tetrakis(hydroxymethyl)phosphonium chloride (THPC). A polymer network deposited using 5 wt% THPC and 10 wt% PEI endows cotton fabric with self-extinguishing behavior during vertical flame testing. The treated cotton maintains high flame retardancy after simulated washing. This coating promotes formation of a continuous intumescent char layer, effectively protecting the cellulose matrix from fire and inhibiting the production of flammable volatiles during pyrolysis and burning. The simplicity and efficacy of this relatively environmentally-benign treatment makes it attractive for replacing halogen-containing and more complex flame-retardant finishing processes.

Thermal and Flammability Properties of Glass Fabric/MWCNT/Epoxy Multilayered Laminates

Multiwalled Carbon Nano Tube (MWCNT) filled glass fabric reinforced epoxy composites (MWCNT/GEC), and neat GEC were prepared by hand-lay-up followed by hot compression molding method. As per the ASTM standard, specimens were prepared and investigated the influence of the addition of MWCNTs on flammability properties of GEC through the UL-94 vertical flammability test and the limiting oxygen index (LOI) method. The thermal degradation was studied by thermogravimetric analysis (TGA). It was found that the GEC improved upon the thermal stability and fire-retardant properties due to the addition of MWCNTs. It was observed that the 0.3 wt.% MWCNTs-glass fabric reinforced epoxy composite (0.3MWCNT/GEC) exhibits better properties than neat GEC and 0.075 wt.% MWCNT-glass fabric reinforced epoxy composite (0.075MWCNT/GEC) and 0.15 wt.% MWCNT-glass fabric reinforced epoxy composites (0.15MWCNT/GEC). Hence, this material may be suitable for electrical devices and appliances based on the other required properties’ further fulfillment.

Preparation and flame retardant properties of cotton fabrics treated with resorcinol bis(diphenyl phosphate)

A flame-retardant agent, resorcinol bis(diphenyl phosphate) (RDP), was synthesized with resorcinol, phenol and phosphorus oxychloride under a catalytic action of magnesium chloride. Synthesized RDP was applied to cotton fabrics with a bridging agent of urea-formalin resin (UFR) to endow them with flame retardancy. The vertical flammability tests were performed, revealing that cotton fabrics treated with 25% RDP and 15% UFR could exhibit the most reasonable flame retardancy. Here, other properties of cotton fabrics, such as mass increment, color change, resistance to washing and hand feeling, were found to be almost unspoiled. The suitable heat-treating condition for temperature and duration was determined to be 160 °C and 2 min. The results of scanning electron micrography, energy dispersive X-ray and Fourier transform infrared spectroscopy showed that RDP was strongly bonded to cotton fiber with a successful bridging action of UFR. Thermogravimetric analysis confirmed that the coated cotton fabrics possessed flame retardant properties.

Calcium Borate Particles: Synthesis and Application on the Cotton Fabric as an Emerging Fire Retardant

ABSTRACT In this study, environmentally benign calcium borate particles (sub-micron size) were synthesized by co-precipitation method and applied on cotton fabric to impart flame retardant property. Synthesized particles were characterized in details to analyze the particle size distribution, crystal structural and chemical constituents. Henceforth, the prepared calcium borate particles were integrated into cotton fabric by following a suitable process condition. Flame retardant efficacy of the treated fabric was analyzed by using vertical flame test and by measuring the limiting oxygen index (LOI) and cone-calorimetry parameters. Besides, particle add-on % on the treated cotton fabric was also optimized (trade-off between efficacy and physiological handle). Optimized concentration of calcium borate particles treated cotton substrate showed a LOI value of around 29 (control cotton fabric having LOI value of 18) and a significant decrease (75% lower as compared to the virgin cotton fabric) in peak heat release rate. Further, thermo-gravimetric analysis and char morphology of control vs. treated substrate were compared to understand the pyrolysis path and carbonaceous structure of cotton substrate, respectively.

Cotton-based flame-retardant textiles: A review

Biodegradable textiles made from cellulose, the most abundant biopolymer, have gained attention from researchers, due to the ease with which cellulose can be chemically modified to introduce multifunctional groups, and because of its renewable and biodegradable nature. One of the most attractive features required for civilian and military applications of textiles is flame-retardancy. This review focuses on various methods employed for the fabrication of cellulose-based flame-retardant cotton textiles along with their developed flame-retardant properties over the last few years. The most common method is to merge N, S, P, and Si-based polymeric, non-polymeric, polymeric/non-polymeric hybrids, inorganic, and organic/inorganic hybrids with cellulose to fabricate flame-retardant cotton textiles. In these studies, cellulose was chemically bonded with the flame-retardants or in some cases, cotton textiles were coated by flame-retardants. The flame-retardant properties of the cotton textiles were investigated and determined by various methods, including the limiting oxygen index (LOI), the vertical flame test, thermal gravimetric analysis (TGA), and by cone calorimetry. This review demonstrates the potential of cellulose-based flame-retardant textiles for various applications.

Effect of treatment‐varying generation number of with hyperbranched polyphosphate ammonium salts on the fire retardant finish performance of cotton fabric

In this study, the aim was to study the effect of the generation number on flame resistant properties of treated fabric. A series of hyperbranched poly phosphate ammonium salts (HBPOPNs) with various generation numbers was successfully prepared by modifying different generations of hydroxyl-terminated hyperbranched polymers (HBPs). The chemical structure of the samples was investigated by Fourier transform infrared spectroscopy, which revealed the presence of a P–O–C covalent bond between cellulose and HBPOPN. The thermal decomposition behavior of the samples was characterized by thermogravimetric analysis. With increasing of generation number (2, 3 and 4), the residues were 31.4%, 33.1%, and 34.8%, respectively, which indicated that the thermal stability of HBPOPN-treated fabric improved with higher generation number. In the vertical flammability test, all samples treated with the different generations of HBPOPN were immediately extinguished after removing the igniter. Values of the limit oxygen index of 42.0, 42.7 and 43.0 were observed with the increase in the generation number (2, 3 and 4) at a concentration of 160 g/L. After 50 laundering cycles (LCs), the LOI values were still remained at 29.3, 29.7 and 29.6. With increasing of generation number, the peak heat release rate and the total heat release of the treated sample decreased slightly. Hyperbranched polymers from the 2nd to the 4th generation could be applied to cotton fabric with excellent flame retardant properties and durability.

Preparation, characterization and testing of flame retardant cotton cellulose material: flame retardancy, thermal stability and flame-retardant mechanism

It is significant to treat cotton fabrics with flame retardant, which can effectively protect them from damage in the fire. A novel reactive flame retardant coating, ammonium salt of N,N-dimethylene-piperazine-(methylphosphonic acid) (ASNDP), was prepared and employed to enhance the anti-burning effect of pure cotton fabrics. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectrum were used to analyze the chemical composition of the synthesized ASNDP. The combustion behavior and anti-burning performance of coated cotton fabrics were fully investigated with using cone calorimetry test, limited oxygen index (LOI) test and vertical flammability test. The total heat release value of the sample coated with ASNDP (450 g/L) decreased to 3.7 ± 0.1 MJ/m2 and the LOI value of the sample with a weight gain of 17.4 ± 0.3% raised to 29.5 ± 0.1%. The thermal and thermo-oxidative stability of coated cotton fabrics were researched with thermogravimetric analysis. The integral procedural decomposition temperature (IPDT) value of coated cotton fabrics in nitrogen atmosphere increased from 610.1 to 1402.8 °C, which proved that ASNDP inhibited the thermal degradation of fiber unit by promoting the growth of the char layer. Besides, the morphological structure of uncoated and coated samples before and after combustion was characterized by scanning electron microscopy. It can be observed that the fiber skeleton of the coated cotton fabrics was evenly distributed and remained intact after combustion. The conclusion was that ASNDP endowed cotton fabrics with good flame retardancy, and effectively performed the flame-retardant effect in both gas phase and the condensed phase. A novel phosphorus–nitrogen synergistic flame retardant containing multiple reactive groups was successfully synthesized and applied to improve the flame retardancy and thermal stability of pure cotton fabrics.

PET Foams Surface Treated with Graphene Nanoplatelets: Evaluation of Thermal Resistance and Flame Retardancy.

In this work, fire-retardant systems consisting of graphene nanoplatelets (GNPs) and dispersant agents were designed and applied on polyethylene terephthalate (PET) foam. Manual deposition from three different liquid solutions was performed in order to create a protective coating on the specimen’s surface. A very low amount of coating, between 1.5 and 3.5 wt%, was chosen for the preparation of coated samples. Flammability, flame penetration, and combustion tests demonstrated the improvement provided to the foam via coating. In particular, specimens with PSS/GNPs coating, compared to neat foam, were able to interrupt the flame during horizontal and vertical flammability tests and led to longer endurance times during the flame penetration test. Furthermore, during cone calorimetry tests, the time to ignition (TTI) increased and the peak of heat release rate (pHRR) was drastically reduced by up to 60% compared to that of the uncoated PET foam. Finally, ageing for 48 and 115 h at 160 °C was performed on coated specimens to evaluate the effect on flammability and combustion behavior. Scanning electron microscopy (SEM) images proved the morphological effect of the heat treatment on the surface, showing that the coating was uniformly distributed. In this case, fire-retardant properties were enhanced, even if fewer GNPs were used.

Thermal insulating and fire-retarding behavior of treated cotton fabrics with a novel high water-retaining hydrogel used in thermal protective clothing

Hydrogel-born fire resistance materials have attracted great attention due to their flame retardance and environmental friendliness. In this work, a facile strategy is presented to prepare a novel hydrogel–cotton fabric laminate with excellent thermal insulation and fire-retarding performance. The hydrogel–fabric laminates exhibited outstanding flame retardant behavior. The flame-retardant mechanism of this system was mainly due to the absorption of a large amount of energy as the water is heated and evaporated in the hydrogel layer. To increase the water retention capacity of the fire-resistant hydrogel, highly hydratable salt (CaCl2) was incorporated into the fire-resistant composite hydrogel composed of poly(N-isopropylacrylamide) (PNIPAAm)/sodium alginate (SA) to prolong water retention time. Here in this work, we aimed to investigate the effect of CaCl2 concentration on water retention capacity, fire-resistant and thermal insulating properties of hydrogel–cotton fabric laminates. Results indicated that the presence of hydratable salt successfully prolonged the water retention time and provided superior fire retardance property over traditional hydrogel. In additional, infrared imaging and vertical flammability test results confirmed that hydrogel–fabric laminates were capable of sustaining 1200 °C for 30 min without the cotton fabric layer burning, whereas natural cotton fabric was completely burned after 12 s. Finally, the hydrogel–cotton fabric laminates exhibited remarkable antibacterial activity against Staphylococcus aureus and Escherichia coli due to incorporated silver nanoparticles in hydrogels, and the bacteriostatic rates both exceeded 96%. The preparation of this hydrogel-born fire resistance materials is facile and can extended the period of protective time as fire resistant clothing for the firefighters.

Eco-friendly and efficient flame-retardant cotton fabric based on a multi-hydroxyl hyperbranched phosphoramidate

A kind of multi-hydroxyl containing hyperbranched phosphoramidate (HPAE) was successfully synthesized and characterized by FT-IR, 1H-NMR, 31P-NMR, and GPC. With the crosslinking of butane tetracarboxylic acid (BTCA), the flame-retardant cotton fabrics were prepared, and the combustion behavior and thermal degradation properties were investigated by limiting oxygen index (LOI), vertical flammability test, cone calorimetry test and thermogravimetric analysis. After treating with 300 g/L HPAE, good flame retardancy was obtained with LOI value of 29.0% and treated cotton fabrics can pass the vertical flammability test without afterflame and afterglow. The peak heat release rate was decreased from 255 to 93 kW/m2 and the total heat release after treatment was reduced by 37%. The thermal stability was greatly improved and over 40% of char residues maintained at 800 °C in N2. The washing durability of HPAE-BTCA treated cotton fabrics was also investigated and LOI value decreased from 29.0 to 25.2% after 25 washing cycles. Besides, the tensile strength, wrinkle recovery angle, and whiteness of cotton fabric after treatment were examined. Overall, our research provides a facile and effective approach to prepare durable flame-retardant cotton fabric, which has great potential in friendly flame-retardant textiles.