The role of natural dyes in the UV protection of fabrics made of vegetable fibres

The safest protection from ultraviolet (UV) radiation exposure is offered by textiles including various apparels, accessories such as hats and shade structures such as umbrellas. Their protectiveness depends on fabric composition, (natural, artificial or synthetic fibres), fabric construction (porosity, weight and thickness) and dyeing (natural or synthetic dyes, dye concentration, UV-absorbing properties, etc.). In this study the UV-protection properties were investigated on fabrics made of vegetable fibres (cotton, flax, hemp and ramie), with different construction parameters (drapery and apparel fabrics), dyed with some of the most common natural dyes. The effect of a tannins-based mordant (the galls of Quercus infectoria) on UV-protection capacity was also tested. UV radiation transmittance of fabrics was measured by two methods: one based on the utilisation of a spectrophotometer equipped with an integrating sphere (in vitro test), and the other based on outdoor measurements taken by a spectroradiometer. Transmittance measurements were used to calculate the Ultraviolet Protection Factor (UPF).Our results revealed that thick and dense (cover factor, CF > 94%) drapery fabrics made of vegetable fibres usually showed good UV-protection levels even if undyed. The use of the tannins-based mordant increased, even without dyeing, the UV-protection level up to the very good and/or excellent protection categories when fabric construction was suitable. Dyeing did not further increase the protection level.Lighter fabrics, usually used for apparel, even showed high UV-protection level after just dyeing, provided that CF was above 94%.Taking into account the high concentrations of dyes used in the present work and the utilisation of mordants containing tannins, slight differences in UV-protection capacity were detected among natural dyes tested and between the two different methods of transmittance measurement. However, UV-protection category defined from outdoor measurements was often higher than that calculated by the in vitro test, indicating an underestimation of the actual protection level of tested fabrics assessed by the latter.     

The role of transition metal cations in dyeing of fabrics made from synthetic fibres

The use of d-metal cations in dyeing polyester fabric with dark blue K increases the dyeability to 350%. Use of VO²⁺, Fe²⁺, and Cu²⁺ cations is most effective. It is hypothesized that d-metal cations increase the number of active sites due to vacant atomic orbitals on the valence level so that the polyester fibre can sorb a larger amount of dye. The use of d-metal cations in dyeing polyester fabric increases the resistance of the color to external physicochemical effects.     

UV absorber aftertreatment to improve lightfastness of natural dyes on protein fibres

The effect of a UV absorber on the lightfastness of natural dyes has been investigated. Wool and silk fabrics, dyed with natural dyes with or without mordants, were aftertreated with two UV absorbers. This treatment improved the lightfastness of the mordant-dyed fabric without affecting its colour or shade. The extent of photofading was evaluated by measuring the colour difference, Δ E , of the dyed sample before and after a 20 h period of irradiation under a xenon arc lamp. The uptake of the UV absorber on wool was much higher than that on silk.     

Diffusion of dyes in natural fibres

This review provides a summary of research on the penetration of dyes into natural fibres. Emphasis is placed on the relationship between diffusion and the structural morphology of the fibres. The types of commonly dyed natural fibres, the methods of measurement of diffusion and the data that have been collected by the use of each method are reviewed. The applicability of general theories of dyeing to natural fibres is also examined. Recent developments that have led to the direct observation of penetration pathways in wool fibres are described, together with the insights obtained into diffusion phenomena. Areas for future work are briefly indicated.     

花生衣天然染料对亚麻织物染色性能研究

以60%乙醇提取花生衣染料,对亚麻织物进行染色。采用直接染色、铁预媒染及铝预媒染3种不同染色方法,研究染色温度和染料用量对亚麻织物染色性能的影响。通过测试染色后织物的K/S以及L、a、b得出最佳染色温度为:直接染色为120℃,Fe⁽²⁺⁾预媒染为110℃,Al(2+)预媒染为110℃,Al⁽³⁺⁾预媒染为120℃。媒染染色织物颜色差异较大,在相同染色条件下,Fe(3+)预媒染为120℃。媒染染色织物颜色差异较大,在相同染色条件下,Fe⁽²⁺⁾预媒染织物K/S值最大。直接染色亚麻织物K/S值高达6,表明花生衣染料对亚麻织物染色潜力大。在最佳染色条件下,染色亚麻织物的色牢度、抗紫外性能优良,Al(2+)预媒染织物K/S值最大。直接染色亚麻织物K/S值高达6,表明花生衣染料对亚麻织物染色潜力大。在最佳染色条件下,染色亚麻织物的色牢度、抗紫外性能优良,Al⁽³⁺⁾预媒染织物各项色牢度可达4级以上,Fe(3+)预媒染织物各项色牢度可达4级以上,Fe⁽²⁺⁾预媒染织物抗紫外性能为原布样的11.8倍。染色后织物荧光性能明显提升,而直接染色最佳。     

Spinning of oxide fibres made of natural cellulose materials

The possibility of obtaining high-melting fibre materials from plant fibres and textile production wastes containing 40–60 wt. % cellulose was demonstrated. The optimum conditions of preliminary chemical treatment of natural raw material to increase the sorption capacity of the materials were determined. The conditions of heat treatment of salt-containing natural fibre materials which would allow regulating the crystal and pore structure of oxide fibres were established. Translated from Khimicheskie Volokna, No. 5, pp. 27–31, September–October, 1997.     

Mechanical properties of polymer composites reinforced with knit fabrics made of high-strength aramid fibres

The possibility of manufacturing knitted fabrics with different properties for reinforcing polymer composites was demonstrated. In making composite materials based on knits, structurally balanced weaves of the 1 + 1 rib and Milan rib type are preferred, since traditional methods of wet heat treatment are unacceptable for knits made of aramid fibres, and for this reason preventing twisting of the fabric is extremely important. The studies showed that the mechanical properties of knit polymer composites are a function of the structure of the knit fabrics to a significant degree and can vary significantly within a wide range. Translated from Khimicheskie Volokna, No. 1, pp. 45-47, January-February, 2009.     

Change in properties of man-made fibres and fabrics made from them under the action of epoxy resins

Conclusions A prolonged action of a toluene solution epoxy resin on polyamide or polyester yarns and fabrics from them causes a change in their geometric characteristics and physico-mechanical properties.This changes are within acceptable limits; therefore textile materials based on the investigated yarns can be used for technological filtration of epoxy resins.Translated from Khimicheskie Volokna, No. 3, pp. 38–39, May–June, 1987.     

Application of rare earth as mordant for the dyeing of ramie fabrics with natural dyes

Selecting appropriate metallic compounds as mordants is essential for dyeing with natural dyes. This paper presents the application of rare earth compounds as mordant for the dyeing of ramie fabrics with four kinds of natural dyes. The influences of pre-mordanting, simultaneous mordanting, and post-mordanting on the dyeing effect were explored. The post-mordanting was proved to give rise to the highest dye uptake. The effects of dyeing conditions including dyeing temperature and time, dyeing bath pH and the concentration of rare earth on the dye uptake were investigated systematically. The fabrics dyed with natural dyes in presence of rare earth as mordant exhibited high color shade stability in the baths with pH varying from being acidic to neutral and alkaline. Employing rare earth as mordant apparently raised the color fastness to washing, rubbing and light of the ramie fabrics dyed with the natural extracts. In comparison with the commonly used metallic salts, using rare earth chlorides as mordants can greatly reduce the ionic concentration employed in natural dyeing. This study proved that rare earth would be a kind or promising environmentally friendly mordant in natural dyeing.     

Protection of textile materials made of different types of fibres from biodeterioration with special dyes

A direct correlation was found between the biological activity of the starting heteryl-containing azo components, azo compounds based on them, and samples dyed with them. With a high proportion of probability, it is possible to note that incorporation of 3,5-dichloropyridyl radical in the molecule of an azo compound causes the appearance of fungicidal activity in the compound. It was found that the biocidal properties of these dyes are a function of the structure of the compound to a greater degree (presence of a concrete heteryl fragment) than of the method of attaching the dye to the fibre. Moscow State Textile Academy; State Scientific-Research Institute of Renovation. Translated fromKhimicheskie Volokna, No. 4, pp. 38–40. July–August, 1999.     

Exploratory results for composites of natural fibres mats with a natural matrix of epoxidized vegetable oils

Composites were prepared by impregnating non-woven mats of mixed natural fibres, mainly flax, hemp and a small percentage of polylactic acid, with an epoxidized soybean oil/maleic anhydride matrix resulting in a composite made up of 85% natural material. These composites comprised 65% matrix resin and 35% natural fibres and were light coloured, and had a good modulus of elasticity and modulus of rupture in the bending mode. The composites made up of 50% matrix resin and 50% natural fibres also gave good results when tested in tension. The best results appear to be obtained by using (i) higher curing temperatures (180?°C) with long post-curing times and (ii) medium temperature (150?°C) and longer press times (360?s).     

The coloration of polypropylene fibres with acid dyes

Modified polypropylene fibre has been prepared by incorporating a polymeric additive into the polypropylene, followed by melt spinning. Fibres with various additive concentrations were dyed with acid dyes, and the amount of dye adsorbed by the fibre was compared with the concentration of dye sites supplied to the fibre by the additive. A diffusion mechanism of dye molecules through interconnected additive particles to the fibre matrix is proposed. Colour yield was assessed by reflectance spectroscopy and photoacoustic spectroscopy. The latter was shown to be particularly suitable for measuring very dark colours. Photoacoustics can also used to detect ring dyeing of fibres at lower additive concentration.     

Estimation of the through porosity of cloth made of chemical fibres in a blend with natural fibres and its correlation with air permeability

The accuracy and reliability of experimental data are determined by the choice of the method of determining the structural characteristics of materials to a significant degree. The data on the level of correlation and the type of functional dependence of the properties on the structure of materials obtained by correlation and regression analysis are a function of the reliability of the experimental data to a significant degree. Of the three methods of estimating the through porosity of materials examined here, the simplest and most widely used method of calculation provides the least reliable results. The most reliable data on through porosity can be obtained by the projection method of indirect estimation of the through porosity and it is recommended for practical research, especially when processing of materials with defined properties is the final goal.St. Petersburg State University of Design and Technology. Translated from Khimicheskie Volokna, No. 3, pp. 31–33, May–June, 1995.     

The adsorption of pyrazolone acid dyes by polyamide fibres

Investigations of the adsorption of acid dyes (l–phenyl–3–methylpyrazolone derivatives) by polyamide fibres have been carried out. It has been found that the adsorption levels are unexpectedly different for various dyes. Some of the dyes, despite high concentration in the dyebath, show adsorption within the limits of what would be predicted by consideration of the amino group content in the amorphous region of the fibre. Other dyes, despite high pH, are characterised by considerably higher adsorption than would be predicted. The results obtained suggest that the increased adsorption of the dyes is brought about by the aggregation of molecules in the fibre into dimers or their multiples.     

Criteria for the affinity of dyes for fibres

An equation was obtained for evaluating the thermodynamic affinity of a disperse dye for a fibre. Quantities Δh _D and K _D , which are functions of the composition of the dye bath, temperature, and state of the fibre material, can characterize the change in the affinity of the dye for the fibre when the dyeing conditions are varied.