Claudio Colleoni

Thermal and fire stability of cotton fabrics coated with hybrid phosphorus-doped silica films

Hybrid phosphorus-doped silica films have been prepared through sol–gel processes to enhance the thermal and fire stability of cotton. To this aim, 3-aminopropyltriethoxysilane and N,N,N′,N′,N″,N″-hexakis-methoxymethyl-[1,3,5]triazine-2,4,6-triamine have been reacted with diethylphosphatoethyltriethoxysilane. FT-IR spectroscopy was exploited for assessing the formation of the silica skeleton on the cotton surface and for evaluating the interactions between the cellulosic fibres and the doped film. The effect of the concurrent presence of Si, P and N on cotton has been investigated by thermogravimetric analyses and the flammability behaviour has been assessed by vertical flammability tests, as well. The sol–gel treatments in the presence of phosphorus and nitrogen turned out to play a protective role on the degradation of the cotton fibres, hindering the formation of volatile species that fuel the further degradation and favouring the formation of a carbonaceous structure.

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.

Hydrophobic behaviour of non-fluorinated sol–gel based cotton and polyester fabric coatings

Water repellency was conferred to cotton and polyester fabrics by an hybrid organic–inorganic finishing obtained by hydrolysis and subsequent condensation of octyltriethoxysilane (OTES) under acidic conditions, in combination with melamine based crosslinking agent N,N,N′,N′,N″,N″-hexakis(methoxymethyl)-1,3,5-triazine-2,4,6-triamine (MF). The application on textile samples was carried out by padding followed by drying and thermal treatment. Water-resistance properties were determined in terms of the contact angle, water uptake and drop adsorption times, whereas the surface composition of treated fabrics was characterized by attenuated total reflectance Fourier transform infrared analyses. Textile fabrics treated with the hybrid OTES–MF sol exhibited the best water-repellent properties, when compared to those treated with OTES or MF finishing alone. In particular, cotton and polyester samples, treated with a 60 g/L MF solution in a 1:4 MF:OTES molar ratio, showed a water contact angle of 130° and 150°, respectively. The high hydrophobicity of the treated fabrics is supposed to be due to the structural and stereochemical properties of the finishing. The presence of the MF triazine ring seems to favour both the improvement of the outward orientation of the OTES alkyl chains, and the crosslinking of N-methylol groups to form a three-dimensional film around the fibres which increases the surface roughness. The contact angle values and the characteristic IR peaks confirmed the presence of the hybrid coating on cotton fabrics even after multiple washing cycles.

Innovative sol-gel route in neutral hydroalcoholic condition to obtain antibacterial cotton finishing by zinc precursor

In the present study, a possibility to realize a transparent sol by zinc-based precursors in a neutral medium without acidic or alkaline catalyst was investigated. Moreover, to study the influence of an inorganic–organic hybrid polymer on the proposed antibacterial finishing, the Zn-based sol was mixed with 3-glycidoxypropyltrimethoxysilane (GPTMS), a hybrid sol–gel precursor, to produce zinc-containing silica coatings on the cotton fibres. An optimization of functionalization process parameters was performed by monitoring survival rate of Escherichia coli bacteria. Finally, selected finishes were tested in respect to their antibacterial activity using potential pathogenic bacteria Staphylococcus aureus and Klebsiella pneumoniae. Sol–gel synthesized cotton finishes based on nano-Zn acetate without and with GPTMS showed larger bactericidal and bacteriostatic activities. The both types of finishes also show hydrophobic effect within the first eliminates the hydrophobicity effect and reduces antibacterial activity. The results are very promising, since the antibacterial activity of cotton is comparably high and the finishing procedure is cheap and can be easily performed.

Flame Retardant Finishing for Textiles

State of the art and perspectives on chemicals and techniques which have been developed in textile finishing for conferring flame retardant properties to natural and synthetic fibres are discussed in this review. An overview on the mechanism of combustion and fire retardancy is reported as well as the chemistry of flame retardants action, the different available types and their uses. The chemistry of molecules used to improve fire retardancy is discussed along with their thermal stabilities and flame-retardant properties. Simplified assumptions about the gas and condensed phase processes of flaming combustion provide relationships between the chemical structure of polymers and fire behaviour, which can be used to design fire-resistant textile materials. Moreover, an overview of currently accepted test methods on textile fabrics to quantify burning behaviour is reported. Finally, as a consequence of increasing commercial demands in terms of cost-effectiveness coupled with increasing concerns about the environmental and general toxicological character of flame retardant additives, some consideration is also given to both the novel approaches of the chemistry of antimony-free and halogen-free flame retardants and to attempts at increasing the efficiency of known chemistry to enhance char formation by intumescent action.

A wearable sweat pH and body temperature sensor platform for health, fitness and wellness applications

The paper presents the development of a compact system able to measure sweat pH, by means of a functionalized textile and a color sensor, and the skin temperature. The aim is to achieve a wearable miniaturized system capable to estimate the body hydration level during exercise or a heat stress. Potential users span from elderly, first responders to athletes. The system has been characterized in the laboratory by using buffer solution, artificial sweat, and an oven for temperature sensor calibrations. Preliminary on-body trials are also reported in the final part of the paper.

A wearable sensor platform to monitor sweat pH and skin temperature

This work presents a wearable sensing system, aimed to monitor sweat pH and skin temperature in a noninvasive way. The wireless interface and the body coupling via a smart textile make it particularly comfortable and unobtrusive for the wearer; the applications extend from high risks patients hydration monitoring in a home-care environment, to fitness and wellness applications.

Low power textile-based wearable sensor platform for pH and temperature monitoring with wireless battery recharge

Wearable sensing electronics is gradually coming to the foreground, due to the increasing awareness for health, environment and pollution matters. The inclusion of sensors into garments represents one of the most comfortable solutions for the wearer; this can be achieved by associating miniaturized electronics with smart fabrics. Basing our experience on previous studies on pH sensing, a novel smart fabric has been developed as a pH-meter: an organic and atoxic halochromic dye is sol-gel fixed on the textile for durability and reversibility purposes, and the readout is performed with a miniaturized novel sensing platform, including extremely low-power color and temperature sensors, wireless data transmission and a wireless battery recharge system. The potential applications vary from sweat pH monitoring for sport performances or medical research, to measurements of environmental conditions.

Sol-gel 3-glycidoxypropyltriethoxysilane finishing on different fabrics: The role of precursor concentration and catalyst on the textile performances and cytotoxic activity

In this paper, the influence of 3-glycidoxypropyltriethoxysilane (GPTES) based organic-inorganic coatings on the properties of treated textile fabrics was studied. All experimental results were deeply analyzed and thereafter correlated with the employed silica precursor concentration and with the presence of the BF3OEt2 (Boron trifluoride diethyl etherate), used as epoxy ring opening catalyst. SEM analysis, FT-IR spectroscopy, X-ray Photoelectron Spectroscopy (XPS), thermogravimetric analysis (TGA) and washing fastness tests of the sol-gel treated cotton fabric samples were firstly exploited in order to characterize the morphological and structural features of the achieved coatings. Finally, the influence of the resulting nanohybrid coatings was explored in terms of abrasion resistance, tensile strength and elongation properties of treated cotton, polyester and silk fabrics. The catalyst amounts seem to strongly improve the formation of coatings, but still they do not influence the wear resistance of treated textile fabrics to the same extent. Indeed, it was found that increasing catalyst/GPTES ratio leads to a more cross linked inorganic 3D-network. GPTES itself was not found to affect the bulk properties of the selected textile and the resulting coatings were not so rigid to hardly modify the mechanical properties of the treated samples. Finally, it is worth mentioning that in all case the obtained 3-glycidoxypropyltriethoxysilane-based chemical finishing have shown no cytotoxic effects on human skin cells.

Vinylphosphonic acid/methacrylamide system as a durable intumescent flame retardant for cotton fabric

A novel intumescent flame retardant treatment, consisting of vinylphosphonic acid (VPA) as the acid source and methacrylamide (MAA) as blowing agent, was designed and applied onto cotton fabrics. The grafting of reactive monomers onto cellulose chains was carried out using potassium persulfate as initiator of a radical polymerization technique. The thermal and fire behaviour of the treated fabrics was thoroughly investigated: in particular, the VPA/MAA coating was able to exert a protective action, giving rise to the formation of a stable swollen char on the surface of textile fibers upon heating, hence improving the flame retardancy of cotton. In addition, the treated fabric achieved self-extinction as assessed by horizontal flame spread tests. Finally, a remarkable weight loss was observed only after the first washing cycle, then the samples did not show any significant weight loss, hence confirming the durability of the self-extinguishing treatment, even after five laundering cycles.