Alessio Montarsolo

Electrospun Porous Mats for High Efficiency Filtration

Submicron size fibers (so-called nanofibers) are easily produced with an electrospinning apparatus from polymer solutions of poly(ethylene oxide), poly(vinyl alcohol), and polyamide-6. Electrospinning seems the most powerful tool for fabricating polymer nanofibers. Fibers were directly deposited in the form of random fiber webs with high area-to-volume ratio and small porous size on ordinary nonwoven filters of PET microfibers. Morphology and diameter distribution of the electrospun filaments were characterized by SEM investigations. The flow resistance of the produced composite filters are evaluated by means of air permeability measurements. The electrospun fibers have diameters ranging from about 70—500 nm and are interconnected each other to form thin webs that have very small pore size. After the electrospinning treatment, the air permeability of the filter media decreases 6—17 times showing a significant change of flow resistance that can be controlled by the thickness of nanofibers layer and the pore size. High efficiency nano-microfibers composite filters could be used in a wide range of applications, ranging from air cleaning for automotive to environment conditioning or liquid filtration.

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.

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.

Electrospinning of polyamide 6/modified-keratin blends

Abstract Protein material resulting from chemical free steam explosion of wool was mixed in different proportion with polyamide 6 in formic acid. The viscosity of the blend solutions decreases with the increase of the protein amount in the blend. Nanofibres produced by electrospinning of these polymer blends show an increase of the filament diameters with increasing protein amounts, except for the 30/70 v/v polyamide 6/protein blend, where nanofibres with “beads” defects were produced. In blend films produced by casting, polyamide 6 crystallize in the form of large spherulites prevalently in the α crystalline structure, while protein is totally amorphous and tends to segregate in the course of drying at room temperature. Otherwise, in electrospun nanofibres polyamide 6 and protein show a better miscibility as suggested by spectroscopic and thermal analysis and polyamide 6 shows a higher thermal stability. Moisture regain and water solubility of blend cast films and electrospun nanofibres respectively were also determined.

Comparative study on the effects of superheated water and high temperature alkaline hydrolysis on wool keratin

The purpose of this work is to understand the impact of superheated water hydrolysis treatment on the chemical properties of wool, and compare it with a conventional method of alkaline hydrolysis. The effects of hydrolysis temperature and concentration of alkali on the properties of wool were investigated. Superheated water hydrolysis was carried out at the temperatures of 140℃ and 170℃, with a material to liquor ratio of 1:3 for 1 hour. In conventional alkaline hydrolysis, the experiments were carried out in the same conditions using potassium hydroxide (KOH) and calcium oxide (CaO) with a concentration in the range of 5%–15% on the fiber weight (o.w.f.). The effects of hydrolysis temperature and alkali concentrations on wool properties were checked using optical and scanning electron microscopy. It was observed that the hydrolyzates obtained in both cases contained low molecular weight proteins and amino acids. Both the hydrolysis processes resulted in degradation of the wool fibers. However, superheated steam hydrolysis is an environmentally friendly and less expensive process, as it is performed using water as a solvent. The wool hydrolyzates produced using superheated water hydrolysis could find a potential application in agriculture, such as fertilization, soil improvement and suchlike.

KES-F Characterization and Hand Evaluation of Oxygen Plasma-Treated Wool Fabrics Dyed at Temperature Below the Boil

In our previous works, we investigated the possibility of reducing the dyeing temperature of wool fabrics with oxygen low-temperature plasma pre-treatment. Fabrics were dyed replicating an industrial process on a laboratory-scale machine, and it was found that pre-treated fabrics could be dyed at 85°C with no worsening of their dyeing performances compared with fabrics conventionally dyed at the boil. In this work, the physical, low-stress mechanical and surface properties of untreated fabrics, untreated fabrics conventionally dyed at 98°C, and plasma-treated fabrics dyed at 85°C, were measured using Kawabata’s Evaluation System for Fabrics. In particular, there were significant increases in bending and shearing characteristic values for plasma-treated fabrics dyed below the boil (85°C). Moreover, subjective hand tests highlighted that these fabrics were stiffer and crisper than the other two types of fabric, thus confirming the results of objective measurements.

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.

A novel synthetic approach to tune the surface properties of polymeric films : ionic exchange reaction between sulfonated polyarylethersulfones and ionic liquids

ABSTRACT Currently, no studies dealing with the role played by ionic liquids on tailoring surface features of polymer films are available. In this work, ionic liquids influence on the surface of sulfonated polyarylethersulfones was investigated. Sulfonated polyarylethersulfones with different degrees of sulfonation were synthesized; their surface properties were modulated through an ionic exchange reaction between the K+ cation of sulfonated polyarylethersulfones and ionic liquids, synthesized changing the length of cation of apolar groups. Hydrophobic properties of sulfonated polyarylethersulfones–ionic liquids films improve with both an increase in degrees of sulfonation and the length of ionic liquids alkyl chains due to higher surface roughness, as shown by scanning electron microscopy and atomic force microscopy. GRAPHICAL ABSTRACT