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Chitosan is a biopolymer with unequalled properties such as biodegradability, nontoxicity, and antimicrobial activity. It is a carbohydrate polymer derived from the deacetylation of the chitin component of the shells of crustacean; hence, it is a renewable material widely available as a byproduct of the food industry. Owing to its extremely interesting properties, chitosan has been extensively applied to textile fibers to confer various functional properties such as • antimicrobial activity with a green chemistry approach for aesthetic, hygienic, and medical applications; • antifelting properties for wool fabrics; • increasing uptake of ionic dyes in dyeing processes; • removal of dyes and other organic pollutants from wastewaters; • removal of heavy metal ions from contaminated wastewaters. A fundamental problem that arises in order to obtain durable chitosan coatings on textiles is due to the low wash fastness of the biopolymer; hence, thermal treatments or cross-linking agents are needed to obtain strong bonding with the fibers. Wet thermal curing involves energy consumption and possible fiber degradation, whereas the most of cross-linking agents such as dialdehydes are toxic. Therefore, many research works were aimed to investigate safer grafting methods with physical means such as UV irradiation or with green chemicals.

The substances responsible for the yellowing of wool treated with nitric acid are two amino acid constituents of the fibre: tryptophan and tyrosine. Nitric acid penetrates the fibres and carries out electrophilic aromatic substitution on the two above-mentioned amino acid residues, producing different colour yields. The intensity of yellowing depends in various ways on the treatment conditions (time, temperature, nitric acid concentration, agitation, and liquor ratio). Yellowing evaluation shows abnormal yellowing depending on acid concentration in the range 5.6-5.9 M. Working in this region makes it possible to use the chromatic reaction in order to show the damage done to wool fibres by the oxidising agents utilised in normal antifelting treatments. Wool damage by the oxidants is usually evaluated by dyeing methods based on different affinity of damaged fibres. By contrast, the xanthoproteic reaction yields chromogens as a function of the accessibility of tryptophan and tyrosine residues for the action of nitric acid on damaged fibres, and can be used for assessing the degree of antifelting treatment and its possible unevenness through the development on the treated wool of a yellow coloration more intense than on untreated wool.

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 degrees 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 degrees 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 degrees 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 degrees C with enzyme pretreatment was found to be optimal taking into account satisfactory washing, perspiration and light fastness values.

Cotton fabrics were water-repellent-finished by radical ultraviolet curing of silicone and urethane acrylates with different formulations. The fabrics were impregnated with undiluted resins and with toluene solutions or water emulsions. Moreover, cationic ultraviolet-curable systems were also investigated, such as an epoxy-functional polysiloxane and mixtures of an epoxy resin with hydroxyl-containing silicone additives. The gel content and polymerization yield were considered for the ultraviolet-curing process evaluation. Water-resistance properties were determined in terms of the contact angle, wettability, moisture adsorption, and water vapor permeability measurements, whereas the morphology and surface composition of treated fabrics were examined with scanning electron microscopy and energy-dispersive X-ray analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The chemical polymerization of pyrrole was studied with the aim of defining the best operating conditions for obtaining conductive fabrics of synthetic fibers. Ammonium persulfate was chosen as the oxidant, and various dopants were tested. Among these, naphtalene-2,6-disulfonic acid disodium salt enabled the lowest surface resistivity to be reached. Hence, several kinetic runs were performed to explain the influence of some operating conditions as oxidant concentration and temperature. A pseudo-first-order kinetic equation was derived, and the reaction rates were found to be practically unaffected by the presence of the textile substrate. Pyrrole polymerization was faster than adsorption of the monomer, suggesting the hypothesis of fast polymerization outside the fibers followed by adsorption onto the fiber surface. The surface coating of polypyrrole was evidenced by microscopic observation of the fiber cross sections. ©2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4121–4126, 2006

The process of silk weighting with methacrylamide (MAA) initiated by ammonium persulfate was studied to optimize the operating conditions to obtain high yields of grafted monomer. The influence of MAA concentration, liquor ratio, concentration of initiator, contact and heating time, acidification, and swelling agents were considered, and optimum operating conditions were outlined. Moreover, various monomethacrylates and dimethacrylates were grafted onto silk as alternative to methacrylamide. Most of these showed graft yields higher than MAA in the same operating conditions and some were found suitable for silk weighting since the weighted fibers show soft hand and good dyeing behavior. DSC and TGA analyses of grafted silk enabled to evaluate the influence of various monomers on the thermal behavior of the weighted fibers. Moreover, on the basis of DSC data, a correlation between the calculated enthalpy of grafted polyMAA and monomer content was studied. The molecular structure of silk grafted with methacrylic monomers was finally characterized by FTIR analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4039–4046, 2007

A series of poly(propylene-glycol-diacrylates) (PPGDA) having molecular weights (MW) in the range 300–3,000 and an acrylic functionality near to two were synthesized by acrylation of the corresponding hydroxy-terminated oligomers with acrylic acid in the presence of p-toluensulphonic acid as a catalyst. The M¯n of the acrylated products was found slightly lower than that of the starting oligomers, indicating the occurrence of an acidic degradation reaction which does not influence the acrylic functionality. The acrylated oligomers were ultraviolet (UV) cured until a complete double bond disappearance was obtained: only in the presence of tripropylene-glycol-diacrylate (TPGDA) were small amounts of residual unsaturations revealed. Rubbery materials were usually obtained, with the exception of TPGDA. The properties of the cured PPGDA were investigated by means of differential scanning calorimetry, thermomechanical analysis, and dynamic mechanical thermal analysis. The Tg values were found to decrease by increasing the MW of the used oligomers, that is, by increasing the length of the chain between the two acrylic double bonds. A good agreement with the Nielsen equation was found. Moreover, the equilibrium swelling values in water were measured; the obtained values were interpreted in terms of the solubility parameters of the oligomers and of the crosslinking density of the networks. Finally, some mixtures of PPGDA oligomers with a typical epoxy-acrylate resin were UV cured; their properties confirm the high flexibilizing effect of the PPGDA oligomers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:491–497, 1997

Three series of poly(alkylene glycol) diacrylates, namely poly(ethylene glycol), poly(propylene glycol) and poly(tetramethylene glycol) α,ω-diacrylates have been prepared by acryloylation of the corresponding bis-OH-terminated oligomers. Their MW was in the range 200-1000 and their acrylic functionality was close to two. They were subjected to UV curing as thin films obtaining, by FTIR analysis, complete terminal double bond conversion in all cases with the exception of the lowest MW oligomers. Thermal and mechanical properties of the networks were investigated by means of DSC, TMA and DMTA analyses. Concerning the PPGDA oligomers, products totally amorphous and rubbery were obtained; PEGDA and PTMGDA oligomers gave similar amorphous structures with the exception of the highest MWs which showed partial crystallinity. By means of thermal and DMTA measurements, Tg values and E' moduli were obtained and correlated to the MW of the oligomers used. In particular, Tg values, as function of the crosslinking density, agreed with those calculated by the Nielsen equation for the three series investigated. The equilibrium swelling in water was determined for various networks as a function of the MW of the oligomers. The values obtained were compared and discussed in terms of the solubility parameters and the crosslinking density of various structures.