Raffaella Mossotti

Hydrorepellent finishing of cotton fabrics by chemically modified TEOS based nanosol

Hydrorepellency was conferred to cotton fabrics by an hybrid organic-inorganic finishing via sol-gel. The nanosol was prepared by co-hydrolysis and condensation of tetraethoxysilane (TEOS) and 1H,1H,2H,2H-fluorooctyltriethoxysilane (FOS), or hexadecyltrimethoxysilane (C16), as precursors in weakly acid medium. The application on cotton was carried out by padding with various impregnation times, followed by drying and thermal treatment, varying the FOS add-on from 5 till 30 % on fabric weight or C16 add-on from 5 to 10 %. Treated samples were tested in terms of contact angles, drop absorption times, washing fastness and characterized by SEM, XPS and FTIR-ATR analyses. In the case of FOS modified nanosol applied with an impregnation time of 24 h or C16 modified nanosol, water contact angles values very close or even higher than 150° were measured, typical of a superhydrophobic surface. The application of the proposed sol-gel process yielded also a satisfactory treatment fastness to domestic washing, in particular for FOS modified nanosol.

Hydrophobic sol-gel finishing for textiles: Improvement by plasma pre-treatment

The surface of cotton (COT) and polyester (PET) fabrics was modified to create a water-repellent finishing by depositing a modified silica-based film using the sol-gel technique. TEOS (tetraethoxysilane)-based physically modified sols with 2% and 11% on weight fabric (o.w.f.) of hydrophobic additives were tested. N-propyltrimethoxysilane (C3), hexadecyltrimethoxysilane (C16) and 1H,1H,2H,2H-fluorooctyltriethoxysilane (FOS) were investigated as additives. Furthermore, a low-temperature plasma pre-treatment was used to activate the COT and PET fabric surface to improve the sol-gel coating adhesion, resistance to abrasion and fastness to washing stresses. A complete chemical/morphological (Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy) and physical characterization (abrasion and air permeability test) of treated samples was carried out. High values of θ (around 140°) on PET and COT samples were obtained with all additives used (C3, C16 and FOS) even at a low concentration (2%). Due to plasma pre-treatment, interesting water-repellent properties were achieved for PET (θ = 148°) treated with TEOS/FOS molar ratio 0.63 and for COT (θ = 140°) with TEOS/C16 molar ratio 0.63. The enhanced coating adhesion, due to plasma surface activation, was confirmed by abrasion and washing tests.

Identification of wool, cashmere, yak, and angora rabbit fibers and quantitative determination of wool and cashmere in blend: a near infrared spectroscopy study

Near infrared spectroscopy coupled with chemiometric analysis was investigated as a fast and non destructive method for the identification of wool, cashmere, yak, and angora rabbit fibers in the raw and combed sliver state and for the quantitative determination of cashmere in cashmere/wool blends. The main differences among spectra of different animal hair arise from physical charateristics rather than chemical characteristics (mainly pigmentation and mean diameter) of animal fibers. The Soft Independent Modelling by Class Analogy method allows the classification of distinct fibers into separate groups with interclass distances ranging from 12.64 for the nearest classes (white cashmere and wool) to above 1000 for the most distant classes of white and pigmented fibers. Percentages of recognition and rejection of 100 % were found with the exception of a yak sample that was not rejected from the pigmented cashmere class (98 % of rejection). The prediction capacity of the model was also evaluated. Quantitative analysis was carried out using samples obtained by carefully mixing known amounts of wool and white cashmere. A standard error of the estimate of 8.5, a standard error of prediction of 13.10 and a coefficient of determination of 0.95 were calculated. From the results obtained, it can be concluded that near infrared spectroscopy can be used as a tool for an initial and rapid screening of unknown animal fiber samples in the raw and combed sliver states and for a fast and coarse estimate of the amount of cashmere in wool/cashmere blends.

Enzyme‐aided wool dyeing with a neutral protease at reduced temperatures

Conventional wool dyeing methods are based on long times at high temperatures. These are energy intensive and can even damage the fibers, thus changing the desired fiber characteristics. In this work, enzyme pretreatment in combination with lower temperatures was used to reach exhaustion values comparable to those obtained with the standard procedure at 98°C. Kinetic runs carried out on wool yarn at different temperatures confirmed the possibility of obtaining more than 90% of bath exhaustion by dyeing at 85°C due to the pretreatment with a proteolytic enzyme. At the same temperature, without enzymatic pretreatment, just 77% of bath exhaustion can be reached. The enzyme action on the dyeing kinetics was investigated through calculation of dye absorption rate constants according to the diffusion‐limited kinetic model proposed by Chrastil. Dynamometric measurements on the yarn dyed at 98°C showed a 25% loss of tensile strength and 50% loss of elongation, while at lower temperature the values were better even after enzyme pretreatment, in agreement with the results of scanning electron microscopy analysis. A temperature of 85°C with enzyme pretreatment was found to be optimal taking into account satisfactory washing, perspiration and light fastness values.

Characterization of Plasma-coated Wool Fabrics

(Si : Ox : Cy : Hz) thin films were deposited on knitted wool fabrics by plasma-enhanced chemical-vapor deposition using hexamethyldisiloxane as a monomer and argon and oxygen as feed gases in low-pressure equipment. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses confirmed the presence of the siloxane coating. The pilling tendency of treated samples was investigated for different deposition powers, ranging from 30 to 50 W. A reduction on pill formation was observed for all treated samples. A silicone-based wet chemical treatment was taken as the reference method for pilling reduction and plasma treatments were compared with it. The pilling grade of treated fabrics was also tested after washing and the results confirmed a good pilling behavior of plasma-treated fabrics. Changes were observed in the bursting resistance of plasma-treated wool samples compared with untreated ones, while no significant differences were found in the whiteness index.

Influence of protease on dyeing of wool with acid dyes

AbstractThe application of enzymes in the wool dyeing process is an important research goal in order to reduce the environmental impact and costs of this finishing process. The work has focused on the possibility of reducing the temperature of conventional dyeing, using an enzymatic pretreatment with a neutral protease to improve the diffusion of the dye into the fibers. After the identification of the optimal dyeing process, the study goes on transferring the method to an industrial application. For this reason the influence of a leveling agent added to the dyeing bath was considered and further tests with an industrial dyeing recipe were performed. In order to evaluate possible fiber damage, samples treated with enzyme were observed by scanning electron microscopy (SEM) and analyzed by gel electrophoresis (SDS-PAGE). Moreover, the variation of tensile strength and elongation of dyed samples were determined. In addition, color fastness to domestic laundering, perspiration and rubbing were carried out. Finally, color measurements and fiber section analysis were performed. The results show the possibility, thanks to the pretreatment with the investigated enzyme, to obtain a homogeneous and solid dyeing on fibers maintaining good mechanical properties, already working at 85°C instead of 98°C currently used in industry.

Mechanical Properties of Silk Yarn Degummed with Several Proteases

Abstract The silk filament spun by the silkworm (Bombyx mori) is composed of two fibroin filaments held together by a cementing layer of sericin. Fibroin and sericin account for about 75 wt% and 25 wt% of the raw silk, respectively. The degumming process consists in removing the sericin layer prior to dyeing using a solution of soap, synthetic detergents, or proteolytic enzymes. Silk yarn was degummed with different commercially available enzymes, two alkaline, a neutral, and an acidic proteases and the results were compared in terms of physical and mechanical properties. Proteases were used under optimum conditions of pH and temperature. The treatments were carried out with three different enzyme dosages, that is, 0.2, 1, and 5 U/g yarn. Soap was taken as the standard method of degumming and enzymatic treatments were compared with this method. The degree of polymerization of silk fibroin was assessed by measuring the intrinsic viscosity of the treated samples.

Electrically conducting linen fabrics for technical applications

Conducting linen fabrics were prepared by the in situ oxidative polymerization of pyrrole using ferric chloride as the oxidant and anthraquinone-2,6-disulfonic acid disodium salt as the dopant to enhance conductivity. The effect of the pyrrole concentration on the final performance and properties of the conducting fabrics was evaluated. Scanning electron microscopy and light microscopy showed a polypyrrole layer deposited on the fiber surface associated with penetration into the bulk fiber at the highest concentrations of pyrrole. Saturation of the amorphous domains of the cellulose structure and coating of the fiber surface resulted in good electrical properties, heat development by the Joule effect and reduced moisture adsorption. The mechanical properties and electrical conductivity of the fabrics were affected by the strong acid conditions of the treatment, but significant electrical properties were achieved while preserving up to 70% of the original tensile strength.

Cotton fabric functionalisation with menthol/PCL micro- and nano-capsules for comfort improvement.

Abstract Objective: Cotton functionalisation with poly-ɛ-caprolactone (PCL) micro- and nano-capsules containing menthol was carried out with the aim of introducing a long-lasting refreshing sensation. Materials and methods: The preparation of the polymer micro- and nano-capsules was carried out by solvent displacement technique. A confined impinging jets mixer was used in order to ensure fast mixing and generate a homogeneous environment where PCL and menthol can self-assemble. Results: The micro- and nano-capsules and the functionalised fabrics were characterised by means of DSC, FT-IR spectroscopy and SEM imaging. Micro- and nano-capsules of different size, from about 200 to about 1200 nm, were obtained varying menthol to PCL ratio (from 0.76 to 8), overall concentration and flow rate (i.e. mixing conditions). The inclusion of menthol was confirmed by DSC analysis. Discussion and conclusion: A patch test was carried out by 10 volunteers. Micro-capsules were found to be effective in conferring the fabric a refreshing sensation without altering skin physiology.

Enzyme-aided wool dyeing: Influence of internal lipids

Dyeing and diffusion properties of dyes into wool fiber are governed by a membranous structure which is formed by a matrix protein and lipid components. External lipids (wool wax) are mainly non-polar, while internal lipids consist mainly of sterols, polar lipids (ceramides), and free fatty acids. These components constitute a real hydrophobic barrier to the diffusion of dye molecules and in fact conventional wool dyeing methods are based on long times at temperature near the boil in order to ensure good levels of dye penetration. To limit the action of this barrier and to achieve higher values of dye bath exhaustion operating at temperatures lower than 98 °C, wool fabric was subjected to three different pre-treatments. The first pre-treatment consisted of the removal of internal lipids by extraction with solvents in order to obtain a higher affinity of the fiber towards the dyes. The second involved hydrolysis with a protease, which leads to the formation of access routes within the fiber to improve the uptake of dyes or other reagents. Finally, the third took into account the combined action of the two previous pre-treatments. The influence of each individual pre-treatment and their combinations on the kinetics and final exhaustion of the dye bath were studied, and assessment of color fastness (to washing and to light) were carried out.