Growth and fire resistance of colloidal silica-polyelectrolyte thin film assemblies

Thin films of colloidal silica were deposited on cotton fibers via layer-by-layer (LbL) assembly in an effort to reduce the flammability of cotton fabric. Negatively charged silica nanoparticles of two different sizes (8 and 27 nm) were paired with either positively charged silica (12 nm) or cationic polyethylenimine (PEI). PEI/silica films were thicker due to better (more uniform) deposition of silica particles that contributed to more than 90% of the film weight. Each coating was evaluated at 10 and 20 bilayers (BL). All coated fabrics retained their weave structure after being exposed to a vertical flame test, while uncoated cotton was completely destroyed. Micro combustion calorimetry confirmed that coated fabrics exhibited a reduced peak heat release rate, by as much as 20% relative to the uncoated control. The 10 BL PEI-8 nm silica recipe was the most effective because the coating is relatively thick and uniform relative to the other systems. Soaking cotton in basic water (pH 10) prior to deposition resulted in better assembly adhesion and flame-retardant behavior. These results demonstrate that LbL assembly is a useful technique for imparting flame retardant properties through conformal coating of complex substrates like cotton fabric.     

Layer-by-layer assembled thin films based on fully biobased polysaccharides: chitosan and phosphorylated cellulose for flame-retardant cotton fabric

Polyelectrolytes multilayer (PEM) films based on fully biobased polysaccharides, chitosan and phosphorylated cellulose (PCL) were deposited on the surface of cotton fabric by the layer-by-layer assembly method. Altering the concentration of PCL could modify the final loading on the surface of cotton fabrics. A higher PCL concentration (2 wt%) could result in more loading. Attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray analysis directly showed that chitosan and PCL were successfully deposited onto the surface of cotton fabric. In the vertical flame test, the cotton fabric with 20 bilayers at the higher PCL concentration (2 wt%) could extinguish the flame. Microcombustion calorimetry results showed that all coated cotton fabrics reduced the peak heat release rate (HRR) and total heat release (THR) relative to the pure one, especially for (CH0.5/PCL2)₂₀, which showed the greatest reduction in peak HRR and THR. Thermogravimetric analysis results showed that the char residue at temperatures ranging from 400 to 700 °C was enhanced compared to that in the pure cotton fabric, especially in the case of higher PCL concentration (2 wt%). The work first provided a PEM film based on fully biobased polysaccharide, chitosan and PCL on cotton fabric to enhance its flame retardancy and thermal stability via the layer-by-layer assembly method.     

Phosphorous-filled nanobrick wall multilayer thin film eliminates polyurethane melt dripping and reduces heat release associated with fire

Unique trilayer (TL) thin films of sodium montmorillonite (MMT), poly(allylamine hydrochloride) (PAH) and poly(sodium phosphate) (PSP) are prepared via layer-by-layer (LbL) assembly. This three-component nanocoating completely shuts down melt dripping and reduces heat release of open-celled flexible polyurethane (PU) foam when exposed to direct flame due to a synergistic interaction between PSP and the thermally shielding clay platelets in the condensed phase. Post burn scanning electron microscopy reveals the nanocoating's swollen morphology is able to maintain foam shape, cellular structure, and porosity. Cone calorimetry reveals that 4 TL coated foams (<3 wt% addition) have a peak heat release rate that is reduced by 54% relative to the uncoated control. Using LbL assembly, this work combines two common flame-retarding mechanisms (thermal shielding clay and intumescing PAH/PSP) in a single coating system and provides a foundational platform for new environmentally-benign flame retardant strategies for various substrates (e.g., foam found in home furnishings).     

Flammability properties of PI fabric coated with montmorillonite

In this study, polyimide (PI) fabric was coated with montmorillonite (MMT) which performed as a kind of flame retardant. Thermogravimetric analysis showed that PI coated with MMT left as much as 69 % char after heating to 700 °C, about 15 % more than uncoated PI fabric. Cone calorimeter testing (heat flux: 60 kW m^?2) showed that coated fabric reduced the total heat release and showed resistance to degradation from direct flame. Post-burn residues of samples were examined with SEM and revealed that the weave structure and fiber shape in all coated fabrics were preserved. In addition, heat-insulting test showed that the temperature difference of coated PI could reach 400 °C after 10 min at 800 °C. These results demonstrate that MMT coating is relatively effective for improving flame-retardant behavior to PI fabric.     

The effect of phosphorus content on the thermal and the burning properties of cotton fabric coated with an ultrathin film of a phosphorus-containing polymer

The effect of phosphorus content on thermal degradation and burning behavior of poly(acryloyloxyethyl diethyl phosphate) or PADEP-coated cotton was studied. The results showed that PADEP-coated cotton prepared by admicellar polymerization using hexadecyltrimethylammonium bromide (HTAB) as a surfactant has higher amounts of phosphorus than that prepared using dodecyltrimethylammonium bromide (DTAB). Higher phosphorus content led to lower decomposition temperatures and greater amounts of char formation after thermal degradation. The effectiveness of the amount of phosphorus on the burning behavior of the treated cotton was investigated by an ASTM flammabilty test. In the case of PADEP-coated cotton prepared with DTAB, the flame spread slowly and extinguished with char formation on the fabric. For untreated cotton however, the flame spread quickly and burned the fabric entirely without char formation. Cotton coated with PADEP using HTAB exhibited self-extinguishing behavior after removing the ignition source. Decrease in decomposition temperature, increase in char formation and the burning behavior of PADEP-coated cotton are all consistent with phosphorus content on the treated fabric.     

Organic–inorganic hybrid silica film coated for improving resistance to capsicum oil on natural substances through sol–gel route

This study concerns the organic–inorganic hybrid coating of silica sol based on dyed cotton, silk and wool fabrics in order to increase the repellence to capsicum oil via adding methyltriethoxysilane, octyltriethoxysilane, hexadec-ltrimethoxysilane or tridecafluorooctyltriethoxysilane (FAS) in the inorganic silica sol. The dyed cotton fabric treated with hybrid silica sol doped with FAS (F-silica sol, FAS 4 %) presents oil-repellent capability, and the contact angles of capsicum oil on the treated cotton, silk and wool fabrics are 98.5°, 111.59° and 122.15°, respectively. A high FAS concentration (20 %) can improve the oil-repellent ability to 5 grades comparing to the untreated fabrics. The color strengths (K/S) of the coated fabrics change slightly, while the maximum absorption wavelengths of the coated fabrics are the same as the untreated fabrics. Although the drape coefficient of cotton fabric is increased to 54 % from 39 % after coated with F-silica sol, the effect is not significant. Compared to the weight gain rate of untreated cotton, silk and wool samples (1.89, 1.23 and 2.38 %), the weight gain rate of the cotton, silk and wool samples coated with F-silica sol are 6.99, 4.76 and 7.69 %, respectively. The calculated sol–gel weight gains (5.10, 3.53 and 5.31 %) of coated fabrics indicate that the silica coating is subsistent on the fiber surfaces.     

The role of pre-hydrolysis on multi step sol–gel processes for enhancing the flame retardancy of cotton

The flame retardancy properties of cotton have been enhanced by exploiting an optimized multistep sol–gel process, consisting of a pre-hydrolysis step, followed by consecutive depositions of hybrid phosphorus-doped silica layers, using DPTS as precursor of the oxidic phases. Upon optimization, it has been demonstrated that just one phosphorus-doped silica layer is able to strongly reduce the heat release rate (?52 %), and the total smoke release (?56 %) and its rate (?62 %) with respect to the untreated fabric. In addition, the deposition of three layers allows achieving a higher flammability resistance if compared to a single layer, as indicated by the final residue after the flammability tests. As far as flammability resistance is concerned, the new coatings have shown a good durability when subjected up to five washing cycles according to ISO 6330 standard.     

Tailoring of multifunctional cellulose fibres with “lotus effect” and flame retardant properties

This research aimed to create multifunctional cellulose fibres with water- and oil-repellent, self-cleaning, and flame retardant properties. A sol mixture of fluoroalkyl-functional siloxane, organophosphonate and methylol melamine resin was applied to cotton fabric by the pad-dry-cure method. Successful coating was verified by atomic force microscopy and Fourier transform infrared spectroscopy. The functional properties of the coated fibres were investigated using the static contact angles of water and n-hexadecane, the water sliding angles, the vertical test of flammability, the limiting oxygen index, and simultaneous thermal analysis. The results reveal that a homogeneous composite inorganic–organic polymer film formed on the cotton fabric surface exhibited the following properties: static contact angle of water of 150° and of n-hexadecane of 128°, water sliding angle of 10°, limiting oxygen index of 34 %, and high thermal stability. These results demonstrate the synergistic activity of the compounds in the coating, which resulted in the creation of a “lotus effect” on the fabric surface as well as excellent flame retardancy and thermal stability.     

PEI/PAA/APP三组分膨胀组装涂层阻燃改性苎麻织物

利用聚乙烯亚胺(PEI)的正电荷性及聚磷酸铵(APP)和聚丙烯酸(PAA)的负电荷性,通过层层组装技术在柔顺多孔的苎麻织物表面交替构筑了(PEI/PAA/PEI/APP)n膨胀型阻燃涂层,并对处理前后的苎麻织物的热稳定性和阻燃性等性质进行了表征.热失重分析(TGA)、微型量热仪(MCC)以及垂直燃烧测试(VFT)结果表明,阻燃处理后织物的热稳定性和阻燃性显著提高.同时与(PEI/APP)n试样相比,引入不同浓度的第3组分PAA在组装层数较少时通过增加PEI的电荷密度等作用可有效增加吸附量从而使上述性能有所提高,层数较高时由于APP和PAA的同性电荷紊乱,阻燃性的提升受到限制.     

Flame-retardant Coating by Alternate Assembly of Poly（vinylphosphonic acid） and Polyethylenimine for Ramie Fabrics

A novel intumescent flame retardant coating,consisting of poly(vinylphosphonic acid)(PVPA) as the acid source and branched polyethylenimine(BPEI) as the blowing agent,was constructed on the surface of ramie fabrics by alternate assembly to remarkably improve the flame retardancy of ramie.The PVPA/BPEI coating on the surface of individual fibers of ramie fabric pyrolyzes to form protective char layer upon heating/burning and improves the flame retardancy of ramie.Thermogravimetric analysis reveals that the PVPA/BPEI-coated ramie fabrics left as much as 25.8 wt% residue at 600 °C,while the control(uncoated) fabric left less than 1.4 wt% residue.Vertical flame test shows that all PVPA/BPEI-coated fabrics have shorter after-flame time,and the residues well preserved the original weave structure and fiber morphology,whereas,the uncoated fabric left only ashes.Microscale combustion calorimetry shows that the PVPA/BPEI coatings greatly reduce the total heat release by as much as 66% and the heat release capacity by 76%,relative to those of the uncoated fabric.     

Applications of micro-scale combustion calorimetry to the studies of cotton and nylon fabrics treated with organophosphorus flame retardants

Effective testing methods are critical for developing new flame retardant textiles by the industry. However, the current testing methods all have limitations. In this research, we applied micro-scale combustion calorimetry (MCC) for evaluating the flammability of the cotton woven fabric treated with a traditional reactive organophosphorus flame retardant in combination with a synergistic nitrogen-containing additive and the nylon-6,6 woven fabric treated with a hydroxyl-functional organophosphorus oligomer and crosslinkers. We found that MCC is capable of differentiating small differences among the treated fabric samples with similar flammability. MCC is able to make quantitative measurement of the peak heat release rate, the most important parameter related to fire hazard of materials, of textile whereas such analysis is more difficult using cone calorimetry due to textile fabrics’ low thickness. By using the thermal combustion parameters measured by MCC, we were able to calculate the limiting oxygen index (LOI) of various treated cotton fabric samples with near-perfect agreement between the experimentally measured and the predicted LOI values of treated cotton fabrics. We also compared the capability of MCC and differential scanning calorimetry for analyzing flame retardant cotton textiles.     

Novel multifunctional water- and oil-repellent,antibacterial, and flame-retardant cellulose fibres created by the sol–gel process

This research aimed to prepare cotton fibres with novel multifunctional water- and oil-repellent, antibacterial, and flame-retardant properties. A three-component equimolar sol mixture, which included 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, and P,P-diphenyl-N-(3-(trimethoxysilyl)propyl) phosphinic amide, was applied to the cotton fabric using the sol–gel process. The presence of the coating on the cotton fibres was confirmed by Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy. The functional properties of the coated cotton fabric were determined from liquid contact angle measurements and antibacterial activity, burning behaviour, and thermo-oxidative stability studies. The results demonstrate that a unique, compatible, and uniform organic-inorganic hybrid polymer network was formed on the fabric surface, which preserved its simultaneous hydrophobic (water contact angle of 135 ± 2°), oleophobic (n-hexadecane contact angle of 117 ± 1°), and bactericidal (bacterial reduction of 100 %) properties and incorporated the enhanced thermo-oxidative stability of the modified cellulose fibres.     

Layer-by-layer assembly of silica-based flame retardant thin film on PET fabric

A novel method to improve flame retardant properties of textile fabric using multilayered thin films was evaluated. In this work, PET fabrics were coated with silica nanoparticles using layer-by-layer assembly. Five bilayers of positively and negatively charged colloidal silica (<10 nm average thickness) increased time to ignition and decreased heat release rate peak of PET fabric by 45% and 20%, respectively. In vertical burn test, this same nanocoating dramatically reduced burn time and eliminated melt dripping. This study demonstrates the ability to impart flame retardant behavior using a water-based, environmentally-friendly protective coating.     

Effects of plasma treatments for improving extreme wettability behavior of cotton fabrics

A simple, environmentally benign and energy efficient process for fabricating single faced superhydrophilic/hydrophobic cotton fabrics by controlling surface texture and chemistry at the nano/microscale is reported here. Stable ultra-hydrophobic surfaces with advancing and receding water droplet contact angles in excess of 146° as well as extreme superhydrophilic surfaces are obtained. Hydrophobic water-repellent cotton fabrics were obtained following plasma treatment through diamond-like carbon (DLC) coating by plasma enhanced chemical vapour deposition. The influence of changing different precursor’s plasma pre-treatments such as H₂, Ar or O₂ on the properties of DLC coatings is also evaluated using atomic force microscopy, X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, and analysed in terms of contact angle measurements. Because of the DLC coating, the coated fabric showed to endure its superhydrophobic character even after 12 months.     

Self-extinguishing cotton fabric with minimal phosphorus deposition

The phosphorus-containing acrylate monomer, 2-acryloyloxyethyl diethyl phosphate (ADEP), was synthesized and applied to cotton fabric by using the admicellar polymerization technique. A cationic surfactant (cetylpyridinium chloride, CPC) was used as the surfactant for admicellar polymerization. Results from FTIR-ATR and SEM showed that PADEP polymer film was successfully formed on the cotton fabric surface. TGA and DTG analyses showed that the phosphorus-containing PADEP lowered the decomposition temperature of the treated fabric resulting in a higher char yield than in the case of untreated cotton. The flammability tests showed that PADEP-coated cotton with the phosphorus content 4.18 mg/g cotton was self-extinguishing, with the flame extinguishing right after the removal of the ignition source leaving a small area of char formation.     

A simple method for determining the total amount of physically and chemically bound water of different cements

A novel environmentally friendly flame-retardant compound, diethyl 3-(triethoxysilanepropyl) phosphoramidate (DTP) was synthesized via a simple one-step procedure with good yield and characterized by FT-IR and ¹H-NMR, ³¹P-NMR and ²⁹Si-NMR. The synthesized compound was coated onto cotton fabrics with different levels of add-ons (5–17 mass%) using the traditional pad-dry-cure method. SEM and XPS were conducted to characterize the surfaces of the coated cotton fabrics. The XPS results showed that DTP was attached to cotton through covalent bond. Cone calorimeter test showed that the cotton fabric treated with DTP became less flammable due to the lower HRR, THR and CO₂/CO ratio. The modified cotton fabrics exhibited efficient flame retardancy, which was evidenced by limiting oxygen index (LOI) and vertical flammability test. Cotton fabrics treated with DTP in 5–17 mass% add-ons had high LOI values of 23–32%. Thermogravimetric analysis results show that the usage of DTP promotes degradation of the cotton fabrics and catalyzes its char formation.     

Coating Cellulosic Material with Ag Nanowires to Fabricate Wearable IR-Reflective Device for Personal Thermal Management: The Role of Coating Method and Loading Level

Textiles coated with silver nanowires (AgNWs) are effective at suppressing radiative heat loss without sacrificing breathability. Many reports present the applicability of AgNWs as IR-reflective wearable textiles, where such studies partially evaluate the parameters for practical usage for large-scale production. In this study, the effect of the two industrial coating methods and the loading value of AgNWs on the performance of AgNWs-coated fabric (AgNWs-CF) is reported. The AgNWs were synthesized by the polyol process and applied onto the surface of cotton fabric using either dip- or spray-coating methods with variable loading levels of AgNWs. X-ray diffraction, scanning electron microscopy (SEM), infrared (IR) reflectance, water vapor permeability (WVP), and electrical resistance properties were characterized. The results report the successful synthesis of AgNWs with a 30 μm length. The results also show that the spray coating method has a better performance for reflecting the IR radiation to the body, which increases with a greater loading level of the AgNWs. The antibacterial results show a good inhibition zone for cotton fabric coated by both methods, where the spray-coated fabric has a better performance overall. The results also show the coated fabric with AgNWs maintains the level of fabric breathability similar to control samples. AgNWs-CFs have potential utility for cold weather protective clothing in which heat dissipation is attenuated, along with applications such as wound dressing materials that provide antibacterial protection.     

Plasma-assisted regenerable chitosan antimicrobial finishing for cotton

In this study, nitrogen-plasma treatment was used to enhance the coating of chitosan onto cotton fabric and chlorine was introduced into nitrogen-containing groups on the chitosan coated fabric in order to make it antimicrobial by chlorination with sodium hypochlorite. The antimicrobial property and its rechargeability were investigated. FTIR, UV and scanning electron microscope were used to evaluate the surface properties, including the existence of chitosan on cotton fabric, the content of chitosan on cotton fabric and the surface topography of cotton fabric after modification. The results showed that nitrogen-plasma introduces nitrogen-containing groups into cotton fabric, the coating of chitosan on fabric was improved with nitrogen plasma treatment and chlorine was introduced into the chitosan coated fabric successfully which inhibits bacteria effectively and it is rechargeable. Thus, the antimicrobial property of cotton fabric coated with chitosan with the aid of nitrogen-plasma treatment after chlorination achieved good effects.     

Thermogravimetric Studies of Deposited Potash Impregnated for Flame-Retardancy into a Cotton Fabric

The effect of potash as a nondurable finish on the flammability of 100% cotton fabric （plain 180 g/m^2） was investigated. The bone-drled weighed fabrics were dipped into suitable concentrations of potash, with a volume of 100 mL at 20-2℃. The impregnation was followed by means of squeeze rolls and drying at 110 ℃. The samples were then reweighed with analytical precision. After conditioning overnight by using our ＂vertical flame tester＂ the optimum add-on values to impart flame-retardancy to cotton fabric was determined and expressed by 0.80 g of potash per 100 g fabric to be an efficient addition. Thermogravimetric analysis of pure cotton, treated cotton with potash at its optimum efficiency for donation of flame-retardancy into cotton fabric was fulfilled and the thermograms were compared and commented. The effectiveness of this hydroxide was attributed to the heat dissipation by the remaining consumed material during the combustion. The results obtained are in favor of ＂Dust or Wall Effect Theory＂.     

Synthesis of gold nanoparticles using herbal Acorus calamus rhizome extract and coating on cotton fabric for antibacterial and UV blocking applications

Gold nanoparticles (AuNPs) have been synthesized by greener method using chloroauric acid as precursor and extract of Acorus calamus rhizome as reducing agent. Formation of AuNP was confirmed by the presence of Surface Plasmon Resonance (SPR) peak in UV–Visible spectral analysis. XRD and FT-IR spectral analyses were performed for characterization. SEM images show spherical morphology and HR-TEM images reveal nanosize of AuNPs. The AuNPs were then coated on cotton fabric by pad-dry-cure method and characterized by SEM with EDAX technique. The results reveal the deposition of AuNPs on the surface of cotton fabric. Uncoated cotton, neat extract coated cotton and extract containing AuNPs coated cotton fabrics were then tested for antibacterial activity against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacterial strains by AATCC 100 test method. It showed that the extract containing AuNPs coated cotton fabric had higher antibacterial activity than other test samples against E. coli. UV-DRS analysis performed on extract containing AuNPs coated cotton fabric showed improved UV-blocking property than uncoated cotton fabric and neat extract coated cotton fabric.