Cotton fabrics treated with hybrid organic–inorganic coatings obtained through dual-cure processes

Cotton fabrics were treated with a hybrid organic–inorganic coating obtained through a dual-cure process, i.e. a photopolymerization reaction followed by a thermal treatment for promoting the formation of silica phases through a sol–gel process. To this aim, different amounts of a silica precursor were added to an acrylic UV-curable formulation in the presence of a suitable coupling agent. The thermo-mechanical properties of the treated fabrics were investigated and correlated to the composition and morphology of the hybrid organic–inorganic system. Furthermore, their flame retardancy and combustion behavior were evaluated by flammability tests and cone calorimetry and compared with the performances of pure cotton.     

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＂.     

表面化学接枝改性阻燃棉织物的制备与性能

采用高碘酸钠对棉织物表面进行选择性氧化生成醛基,选取乙二胺与醛基反应,通过膦氢化加成反应将阻燃剂亚磷酸二甲酯接枝到棉织物表面,最后通过三羟甲基三聚氰胺对棉织物表面进行接枝改性,制备了含三羟甲基三聚氰胺/乙二胺/亚磷酸二甲酯阻燃棉织物.通过傅里叶红外光谱（FTIR）对改性后棉织物的结构进行了表征,通过极限氧指数（LOI）测试研究了其阻燃性能,通过锥形量热测试研究了其燃烧行为,通过在40℃皂水中洗涤10次考察了其耐水性能,通过扫描电子显微镜测试了其表面及燃烧后炭层的形貌.研究结果表明,经表面改性后,棉织物的LOI值由（19.5±1.0）%提高到了（43.1±1.0）%,经耐水洗测试后,LOI值仅下降至（42.6±1.0）%,保持了非常好的阻燃性能,表明通过表面接枝方法制备的三羟甲基三聚氰胺/乙二胺/亚磷酸二甲酯阻燃棉织物具有非常好的耐水洗性能.表面阻燃改性提高了棉织物在燃烧过程中的成炭性能,形成的连续膨胀的炭层较好地保护了内部织物,抑制了织物的降解和燃烧,从而提高了棉织物的阻燃性能.     

A Thermogravimetric Study of Cotton Fabric Flame‐Retardancy by Means of Impregnation with Red Phosphorus

The effect of red phosphorus was found to be effective for flame‐retardancy of a pure cotton fabric. The laundered bone‐dried weighed samples were impregnated with red phosphorus at suitable concentrations. Vertical flame spread test was accomplished. The optimum add‐on value to impart flame‐retardancy onto cotton fabric was determined around 3.95 g of red phosphorus per 100 g of fabric. TG/DTG curves of treated samples showed a well‐timed weight loss occurred with regard to untreated specimens. This illustrates the sufficiency of impregnation and support its catalytic action on flame‐retardancy, which is compliance with data obtained via flammability test. The results are in favor of "Chemical Action Theory", "Gas Theory" and "Condensed Phase Retardation".     

Modified Silica Sol Coatings for Water-Repellent Textiles

The preparation of water repellent textiles by coating with different modified silica sols has been investigated. For this, pure and with 3-glycidoxypropyl triethoxysilane co-condensed silica sols were modified by three types of additives: alkyltrialkoxysilanes, polysiloxane derivatives and a fluorine containing silane. Hydrophobic properties of the coated fabrics of polyamide and of polyester mixed with cotton were determined using contact angle measurements. The hydrophobicity increases with increasing concentration of the alkylsilane additive in the silica sol and the length of the alkyl chain but with high additive concentrations plateau values in hydrophobicity were reached. Analogously textile coatings with high hydrophobicity were gained using hydrophobic polysiloxane or fluorine containing silicon compounds. The comparison of the different variants reveals that high wash-out stabilities were reached only by silica sols containing fluorine compoundsand hexadecylsilane additives. Therefore long-chain alkyltrialkoxysilane compounds could be used as substitutes for fluorine compounds for the surface modification of textiles in some practical applications.     

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 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.     

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.     

The comparison of differences in flammability and thermal degradation between cotton fabrics treated with phosphoramidate derivatives

The effectiveness of a phosphoramidate tetraethyl piperazine‐1,4‐diyldiphosphoramidate (TEPP) as a flame retardant on cotton twill fabrics was compared with that of a previously studied diethyl 4‐methylpiperazin‐1‐ylphosphoramidate (DEPP). TEPP was formed in a reaction between two phosphonates and a piperazine then cotton twill fabrics were treated with TEPP at different levels of add‐on (2–19 wt%) and characterized using vertical flammability, limiting oxygen index, microscale combustion calorimetry, and thermogravimetric analysis methods. The results showed better flame retardancy and thermal behavior for TEPP fabrics when compared with DEPP fabrics. When the morphological structure of the formed char from the burned areas was examined by scanning electron microscopy, the results revealed a fairly insignificant difference in the mode of action between the two types of fabric. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Investigation of the flammability of different textile fabrics using micro-scale combustion calorimetry

Evaluating and analyzing the performance of flame retardant (FR) textiles are a critical part of research and development of new FR textiles products by the industry. The testing methods currently used in the industry have significant limitations. Most analytical and testing techniques are not able to measure heat release rate (HRR), the single most important parameter in evaluating the fire hazard of materials. It is difficult to measure HRR of textile fabrics using cone calorimetry because textile fabrics are dimensionally thin samples. The recently developed micro-scale combustion calorimetry (MCC) is able to measure the following flammability parameters for textile using milligram sample sizes: heat release capacity, HRR, temperature at peak heat release rate (PHRR), total heat release and char yield. In this research, we applied MCC to evaluate the flammability of different textile fabrics including cotton, rayon, cellulose acetate, silk, nylon, polyester, polypropylene, acrylic fibers, Nomex and Kevlar. We also studied the cotton fabrics treated with different flame retardants. We found that MCC is able to differentiate small differences in flammability of textile materials treated with flame retardants. We were also be able to calculate the limiting oxygen index (LOI) using the thermal combustion properties of various textile samples measured by the MCC. The calculated LOI data have yielded good agreement with experimental LOI results. Thus, we conclude that MCC is an effective new analytical technique for measuring textile flammability and has great potentials in the research and development of new flame retardants for textiles.     

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.     

TG comparison between the efficiency of deposited ammonium bromide and ammonium chloride on the flame-retardancy imparted to cotton fabric

This study investigates the effect of ammonium bromide and/or ammonium chloride as nondurable finishes on the flammability of 100% cotton fabric, (woven construction, weighing 144 g m⁻²). The laundered bone-dried, weighed fabrics were impregnated with suitable concentrations of aqueous ammonium bromide and/or ammonium chloride solutions by means of squeeze rolls and dried at 110°C for 30 min. Afterwards they were cooled in a desiccator, re-weighed with an analytical precision and kept under ordinary conditions before the fulfillment of the vertical flame test. The optimum add-on values to impart flame retardancy expressed in g anhydrous ammonium bromide and ammonium chloride per 100 g fabrics were individually obtained to be about 3.5–3.89 and 17.31–17.99%, respectively. Thermogravimetric analysis (TG/DTG) of pure cotton and the salts treated fabrics were fulfilled and their curves were compared and commented. The results obtained comply with free radical theory, and also proved the superiority of ammonium bromide for the impartation of flame-retardancy in regard to ammonium chloride.     

Immobilization and electrochemistry of cytochrome c on amino-functionalized mesoporous silica thin films

The immobilization and electrochemistry of cytochrome c (cyt c) on amino-functionalized mesoporous silica thin films are described. The functionalized silica films with an Im3m cubic phase structure were deposited on conducting ITO substrate by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of Pluronic F127 under acidic conditions. The high specific surface area, large pore size and functional inner surface of mesoporous silica thin films result in a high cyt c loading, and the cyt c immobilization on this silicate framework is stable. After adsorption of cyt c, the ordered cubic structure of mesoporous silica and the redox activity of immobilized cyt c are retained as demonstrated by X-ray diffraction (XRD), Transmission electron microscope (TEM) and cyclic voltammetry. The redox behavior of the cyt c/silica film-modified ITO electrode is a surface-controlled quasi-reversible process for the experimental conditions used in this work and the electron transfer rate constant is calculated is 1.33 s⁻¹. The ITO electrode modified by cyt c/silica film possesses a high stability; even cyt c retains its redox activity following immobilization for several months. Furthermore, the electrocatalytic activities of the modified ITO electrode to hydrogen peroxide and ascorbic acid have been studied. Since these behaviors are quite pronounced, the modified electrode can be used for detection of hydrogen peroxide and ascorbic acid.     

Antimicrobial coatings on textiles–modification of sol–gel layers with organic and inorganic biocides

Antimicrobial textile materials were produced by sol–gel coatings with embedded biocidal compounds. For preparation a sol–gel procedure was used, starting from pure silica sols and 3-glycidyloxypropyltriethoxysilane (GLYEO) containing silica sols. These sols were modified with silver compounds, hexadecyltrimethyl-ammonium-p-toluolsulfonat (HTAT) and copper compounds, respectively. The investigations were performed on viscose fabrics as function of the concentration of biocidal compounds and of thermal treatment of textile after dip-coating between 80 up to 180 °C. The use of modified silica coatings leads to a decreased growth of fungi (Aspergillus niger) and bacteria (Bacillus subtilis and Pseudomonas putida) with increasing amount of the biocide embedded in the coating. The addition of GLYEO supports the biocidal effect of the coatings and enhances the stability of the coating solutions. For preparation of antimicrobial silica coatings the biocides silver, copper or HTAT can be used alone but the combination of these compounds leads to enhanced results against both fungi and bacteria. Therefore silica sols containing a combination of different types of biocides may be used for antimicrobial modification of textiles in some practical applications. For industrial applications the here presented coating solutions are especially advantageous, because of 90% water content in the solvent.     

Thermal properties of cotton fabric modified with poly (propylene imine) dendrimers

For the first time, thermal stability and flame retardant properties of cotton fabrics modified with poly (propylene imine) dendrimer (PPI-dendrimer) using cross linking agents have been reported. The PPI-dendrimers can be considered as novel nitrogen flame retardant agents, because they contain a large number of nitrogen-containing groups (amine end groups), which may release nitrogen gas or ammonia. In this paper, the effect of the PPI-dendrimers on thermal behavior of cotton fabric is investigated through thermogravimetric analysis, differential scanning calorimetry, flammability (in vertical configuration) and limiting oxygen index tests. Indeed, both thermal stability and flame retarancy of the modified fabrics have significantly enhanced. Furthermore, field emission scanning electron microscopy micrographs have been studied in order to evaluate morphology of the cotton samples. Crystallinity and physical properties including crease recovery angle, breaking strength, whiteness index and hygroscopicity of the samples have been also assessed.     

Active antibacterial coating of cotton fabrics with antimicrobial proteins

The prevention of bacteria colonization by immobilizing proteins with antimicrobial activity onto cotton fabrics was investigated. Such coatings have potential applications in medical dressing materials used in wound care and healing. Two antimicrobial proteins lysozyme and hydramacin-1 (HM-1) were surface immobilized through two linkers (3-aminopropyl) triethoxysilane (APTES) and citric acid in the presence of the water soluble carbodiimide coupling reagent 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate. Surface composition analysis by attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopies confirmed formation of the protein-cellulose conjugates. Antimicrobial activities of the different functionalized surfaces were found to vary between APTES and citric acid directed coatings. Citric acid immobilized lysozyme treated samples demonstrated superior activity against Gram-positive Bacillus subtilis, whereas APTES immobilized HM-1 treated samples demonstrated an advantage in inhibiting the growth of Gram-negative Escherichia coli. The antibacterial activity and stability of citric acid immobilized protein fabrics following sonication, boiling and chemical treatment were noticeably higher than that of the corresponding APTES immobilized protein fabrics. The dual coating of fibers with both antimicrobial proteins afforded efficient antimicrobial activities against both bacterial species. The results suggest that coating cotton fibers with antimicrobial proteins and peptides represents a feasible approach for developing active surfaces that prohibit growth and colonization of bacterial strains and can be potentially used in medical cotton-based fabrics.

     

Sol–gel treatments for enhancing flame retardancy and thermal stability of cotton fabrics: optimisation of the process and evaluation of the durability

Cotton fabrics have been treated by sol–gel processes in order to create a silica compact coating on the fibres to enhance their thermal stability and flame retardancy. The effect of process parameters such as silica precursor:water molar ratio and drying conditions (temperature and time) has been thoroughly investigated, aiming at optimization of target properties. Thermogravimetry and cone calorimetry have been respectively used to assess thermal stability and combustion behaviour of treated fabrics. Coating durability to different washing programmes has been evaluated as well.     

Scratch-Resistant Improvement of Sol-Gel Derived Nano-Porous Silica Films

Scratch-resistance of sol-gel derived nano porous silica films were studied. The thin films were prepared with a dip-coating method from both one-step and two-step catalyzed silica sols, and treated in a mixture gas of ammonia and water vapour afterwards. The thin films were characterized by using Atomic Force Microscope (AFM), ellipsometer, Fourier-transform Infrared Spectroscope (FTIR), respectively. Experimental results have shown that the two-step catalysis remarkably improves strength of the films, and abrasion-resistance and adhesion of the silica films were further increased after the mixture gas treatment. It is attributed to the cross-linking of silica particles in the sols by randomly branched or/and entangled linear chains and more Si–O–Si bonds formed by the mixture gas treatment.     

Development of an environmentally friendly halogen‐free phosphorus–nitrogen bond flame retardant for cotton fabrics

A novel flame retardant diethyl 4‐methylpiperazin‐1‐ylphosphoramidate (CN‐3) containing phosphorous and nitrogen was prepared. Its chemical structure was confirmed by nuclear magnetic resonance (¹H‐, ¹³C‐, and ³¹P‐NMR), Fourier transform infrared spectroscopy, and elemental analysis. Print cloth and twill fabrics were treated with CN‐3 to achieve different levels of add‐on (7–22 wt% add‐ons for print cloth and 3–18 wt% add‐ons for twill). Thermogravimetric analysis, vertical flame test, and limiting oxygen index (LOI) were performed on the treated cotton fabrics and showed promising results. When the treated print cloth and twill fabric samples were tested using the vertical flame test (ASTM D6413‐08), we observed that the ignited fabrics self‐extinguished and left behind a streak of char. Treated higher add‐ons fabrics were neither consumed by flame nor produced glowing ambers upon self‐extinguishing. LOI (ASTM 2863–09) was used to determine the effectiveness of the flame retardant on the treated fabrics. LOI values increased from 18 vol% oxygen in nitrogen for untreated print cloth and twill fabrics to maximum of 28 and 31 wt% for the highest add‐ons of print cloth and twill, respectively. The results from cotton fabrics treated with CN‐3 demonstrated a higher LOI value as well as a higher char yield because of the effectiveness of phosphorus and nitrogen as a flame retardant for cotton fabrics. Furthermore, FT‐IR and SEM were used to characterize the chemical structure on the treated fabrics as well as the surface morphology of char areas of treated and untreated fabrics. Published 2012. This article is a US Government work and is in the public domain in the USA.