Methods of coating textiles with soluble conducting polymers

Soluble conducting alkyl polypyrrole polymers have been applied by either chemical polymerization of the 3-alkyl monomers or direct application of polymer emulsion to the surface. Solution, vapor and spray polymerization methods of coating poly(3-alkylpyrroles) to the surface of woven wool fabrics are explored. Conductive textile samples have also been prepared by applying emulsions of soluble prepolymerized 3-alkylpyrrole to the fabric surface. Direct applications of a conductive paint to the textile surface eliminate the exposure of the substrate to damaging oxidizing agents which allow the coating of more sensitive and delicate substrates. All textiles produced are tested for abrasion resistance and conductivity. For alkyl polypyrrole coated fabrics, the optimum carbon chain lengths are between n=10 and n=14, which result in optimum values of conductivity and solubility. The darkness of the tone is inversely related to the surface resistivity of the resulting conductive fabric. Therefore, deep black coatings have low resistivity whereas light gray coatings on a white fabric surface have higher surface resistivity. Longer alkyl chains result in higher surface resistivity in fabrics. The conductive coating of poly(3-decanylpyrrole) on the textile surface has a better abrasion resistance compared to that of an unsubstituted polypyrrole coating.

Directional water-transport fabrics achieved by wettablity gradient from superhydrophobicity to hydrophilicity

In this study, we demonstrate that fabrics having a wettability gradient from superhydrophobic to hydrophilic through the thickness direction show a novel directional water transfer effect: water can transfer only from the superhydrophobic to the hydrophilic side, but not in the opposite direction unless an external force is applied. A sol-gel technology was used to prepare a superhydrophobic coating on fabrics, and the coated fabrics showed water contact-angle as high as 165°. When the coated fabric was subjected to a photochemistry treatment from one fabric side, the irradiated surface turned hydrophilic permanently, while the back side still maintained the superhydrophobicity. The treated fabric can transfer water droplet rapidly from hydrophobic to hydrophilic side, and the pressure allowing water breakthrough the fabric is different considerably between the two fabric sides. The directional water transfer effect is also affected by the wettability gradient. Such a directional water transfer coating may be useful to develop new functional fabrics for defence applications.

Wettability gradient-driven directional water transport across thin fibrous materials

Recently, novel properties have been observed when superhydrophobic and superhydrophilic surfaces are combined. For example, the Stenocara beetle, an insect in the Namib Desert, has an incredible ability to capture fresh water from air for its survival in the dry desert environment [1]. Such a feature derives from its special wing that has a hydrophilic-patterned superhydrophobic surface. Materials having a similar surface feature also exhibited a similar water-harvesting function [2]. A spider silk has been reported to show a periodic alternation of hydrophobic and hydrophilic surfaces along the fiberlength direction [3], which can quickly collect water from air. It was also observed that water droplets moved in one direction along a superhydrophobic-to-superhydrophilic gradient surface [4]. However, all these works are based on two dimension surfaces. The work on water transfer through porous media induced by a gradient wettability change has received little attention until very recently [5]. In this study, we have developed a simple, but very effective and versatile, method to produce wettability gradient across the thickness of fabrics, and demonstrated that the fabrics have the ability to spontaneously transfer water unidirectionally through the fibrous architecture. A plain weave polyester fabric was mainly used as a sample material.

The impact of textile wet colouration on the environment in 2011

Wet textile colouration has the highest environmental impact of all textile processing steps. It consumes water, chemicals and energy and produces liquid, heat and gas waste streams. Liquid effluent streams are often quite toxic to the environment. There are a number of different dyeing processes, normally fibre type specific, and each has a different impact on the environment. This research investigated the energy, chemical and water requirements for the exhaust colouration of cotton, wool, polyester and nylon. The research investigated the liquid waste biological and chemical oxygen demand, salinity, pH and colour along with the energy required for drying after colouration. Polyester fibres had the lowest impact on the environment with lowest water and energy consumption in dyeing, good dye bath exhaustion, the lowest salinity levels in their effluent, relatively neutral pH effluent and low energy in drying. The wool and nylon had similar dye bath requirements and outputs however the nylon could be dyed at far lower liquor ratios and hence provided better energy and water use figures. The cotton and wool required high energy consumption in drying after colouration. Cotton performed poorly in all of the measured parameters.

Unidirectional water transfer effect from fabrics having a superhydrophobic-to-hydrophillic gradient

In this study, we demonstrate that fabrics having a wettability gradient from superhydrophobic to hydrophilic through the thickness direction show a novel directional water transfer effect: water can transfer from the superhydrophobic to the hydrophilic side, but not in the opposite direction unless an external force is applied. A sol-gel technology was used to prepare a nano-structured superhydrophobic coating on fabrics, and the coated fabrics showed water contact-angle as high as 165 degrees. When the coated fabric was subjected to a photochemistry treatment from one fabric side, the irradiated surface turned hydrophilic permanently, while the back side still maintained the superhydrophobicity. The treated fabric can transfer water droplet rapidly from hydrophobic to hydrophilic side, and the pressure allowing water breakthrough the fabric are different considerably between the two fabric sides. The directional water transfer effect is affected by the wettability gradient. Such a directional water transfer coating may be useful to develop new functional fabrics for defence applications.

Mobile agent tracking with single frequency continuous wave radar : a linear robust filtering based approach

3-alkylpyrrole to the fabric surface. Direct applications of a conductive paint to the textile surface eliminate the exposure of the substrate to damaging oxidizing agents which allow the coating of more sensitive and delicate substrates. All textiles produced are tested for abrasion resistance and conductivity. For alkyl polypyrrole coated fabrics, the optimum carbon chain lengths are between n=10 and n=14, which result in optimum values of conductivity and solubility. The darkness of the tone is inversely related to the surface resistivity of the resulting conductive fabric. Therefore, deep black coatings have low resistivity whereas light gray coatings on a white fabric surface have higher surface resistivity. Longer alkyl chains result in higher surface resistivity in fabrics. The conductive coating of poly(3-decanylpyrrole) on the textile surface has a better abrasion resistance compared to that of an unsubstituted polypyrrole coating.

Optimization of polymerization conditions and thermal degradation of conducting polypyrrole coated polyester fabrics

PET fabric is coated with conducting polypyrrole (PPy) by oxidative polymerization from an aqueous solution of Py using ferric chloride hexahydrate (FeCl3) as oxidant and p-toluene sulphonate (pTSA) as dopant. The optimum concentrations for Py, FeCl3 and pTSA were found to be 0.11, 0.857 and 0.077 mol/l respectively, which yielded a conductive fabrics with resistivity as low as 72 Ω/sq. PPy fabric gained resistivity less than one order of magnitude when aged for 18 months at room temperature. The stabilizing effect of the dopant pTSA against thermal degradation was demonstrated; the undoped samples reached resistivity of around 40 kΩ, whereas doped samples reached less than 2 kΩ at the same temperature and time.

The impact of textile wet colouration on the environment in 2011

Wet textile colouration has the highest environmental impact of all textile processing steps. It consumes water, chemicals and energy and produces liquid, heat and gas waste streams. Liquid effluent streams are often quite toxic to the environment. There are a number of different dyeing processes, normally fibre type specific, and each has a different impact on the environment. This research investigated the energy, chemical and water requirements for the exhaust colouration of cotton, wool, polyester and nylon. The research investigated the liquid waste biological oxygen demand, total organic carbon dissolved solids, suspended solids, pH and colour along with the energy required for drying after colouration. Polyester fibres had the lowest impact on the environment with low water and energy consumption in dyeing, good dye bath exhaustion, the lowest dissolved solids levels in waste water, relatively neutral pH effluent and low energy in drying. The wool and nylon had similar dyebath requirements and outputs however the nylon could be dyed at far lower liquor ratios and hence provided better energy and water use figures. Cotton performed badly in all of the measured parameters.

Antibacterial activity of capsaicin-coated wool fabric

Fabrics made from natural fibers, such as wool and cotton, are susceptible to attacks from micro-organisms, which may damage the fabrics and harm the human body. Antimicrobial finishing of natural textile products may involve harmful and non-environmentally friendly chemicals. In this study, a natural antibacterial agent, capsaicin, was coated on the surface of wool fabrics by a sol-gel process. The antibacterial properties of coated fabrics were evaluated against test bacteria Escherichia coli according to the American Association of Textile Chemists and Colorists (AATCC) method and standard American Society for Testing and Materials (ASTM) E2149-01. Compared with the control group (sol-gel coated fabric without capsaicin), the capsaicin-coated fabric inhibited bacterial growth markedly after 24 hours incubation at 37°C. The antibacterial efficiency after laundry washes was also investigated. Good durability to washing of capsaicin on fabric was achieved by the sol-gel coating technique.

Photoreactive azido-containing silica nanoparticle/polycation multilayers : durable superhydrophobic coating on cotton fabrics

In this study, we report the functionalization of silica nanoparticles with highly photoreactive phenyl azido groups and their utility as a negatively charged building block for layer-by-layer (LbL) electrostatic assembly to produce a stable silica nanoparticle coating. Azido-terminated silica nanoparticles were prepared by the functionalization of bare silica nanoparticles with 3-aminopropyltrimethoxysilane followed by the reaction with 4-azidobenzoic acid. The azido functionalization was confirmed by FTIR and XPS. Poly(allylamine hydrochloride) was also grafted with phenyl azido groups and used as photoreactive polycations for LbL assembly. For the photoreactive silica nanoparticle/polycation multilayers, UV irradiation can induce the covalent cross-linking within the multilayers as well as the anchoring of the multilayer film onto the organic substrate, through azido photochemical reactions including C–H insertion/abstraction reactions with surrounding molecules and dimerization of azido groups. Our results show that the stability of the silica nanoparticle/polycation multilayer film was greatly improved after UV irradiation. Combined with a fluoroalkylsilane post-treatment, the photoreactive LbL multilayers were used as a coating for superhydrophobic modification of cotton fabrics. Herein the LbL assembly method enables us to tailor the number of the coated silica nanoparticles through the assembly cycles. The superhydrophobicity of cotton fabrics was durable against acids, bases, and organic solvents, as well as repeated machine wash. Because of the unique azido photochemistry, the approach used here to anchor silica nanoparticles is applicable to almost any organic substrate.

Study on the dyeing properties of hemicyanine dyes. I. Acrylic fabrics

Three hemicyanine dyes were employed in dyeing acrylic fabrics following traditional cationic dyeing procedures. The influence of the substituting groups of the dye molecule on the sorption rate and sorption isotherms was analyzed. The results showed that those dyed acrylic fabrics using hemicyanine dyes had obvious fluorescent effect in the spectra range 550–750 nm. In addition, according to the EN-471 standard (2003), the chromaticity of dyed acrylic fabric was calculated to evaluate whether hemicyanine dye could meet the requirements of the fluorescent dye for high visibility warning clothing.

Photochromic fabrics with improved optical performance

In this PhD project, the photostability and colour depth of photochromic fabrics prepared by a hybrid silica coating were improved and the relationship between the pore structure of the silica coatings and the photochromic properties of the coated fabrics was investigated.