Nano zinc oxide for UV protection of textiles

This paper describes the effect on the fading of dyed polyester fabrics in artificial sunlight, when the Ultra Violet (UV) component of the radiation was blocked by coating the fabric with zinc oxide nanoparticles, dispersed in an acrylic polymer. Zinc oxide is photoactive and generates superoxide and hydroxyl radicals (Reactive Oxygen Species; ROS) when irradiated with UV in the presence of oxygen and water. The results for the four dyes studied show that different dye chromophores interact differently with ROS. Selection of dyes with anti oxidant properties or addition of other anti oxidants may reduce the adverse effects of ROS

Polymer coatings containing nano particles of zinc oxide for the UV protection of dyed polyester fabrics

The useful life of many outdoor textile products is limited by degradation caused by exposure to sunlight, in particular by the ultra violet component (below 400 nm). The degradation results in fading of colours and also loss of physical properties, such as tear strength and abrasion resistance. Degradation can be decreased with UV absorbers, often used in conjunction with antioxidants or free radical quenchers. The protection afforded by these organic compounds is, however, limited as they are ultimately destroyed by the UV radiation they absorb.
An alternative approach is to coat fabrics with a polymer containing an inorganic UV absorber, such as zinc oxide. The inherent stability of zinc oxide would be expected to provide a protective effect over a much longer period than can be achieved with an organic UV absorber. A possible disadvantage of zinc oxide when applied in a polymer film is that absorption and scattering of visible light can produce hazy films and, hence, an unacceptable change in fabric appearance.
This poster paper examines the possibility of using nano particles of zinc oxide dispersed in acrylic polymers for protecting dyed polyester fabrics against sunlight fading. Factors affecting both UV absorbance and film clarity will be discussed. The possibility will also be examined that the protective effect may be reduced in some circumstances by reactive oxygen species, generated by the interaction of UV with zinc oxide in the presence of air and water.

Reduction of the photocatalytic activity of ZnO nanoparticles for UV protection applications

The detrimental effects of UV radiation are having a significant impact on our life and environment. The development of effective UV shielding agents is therefore of great importance to our society. ZnO nanoparticles are considered to be one of the most effective UV blocking agents. However, the development of ZnO-based UV shielding products is currently hindered due to the adverse effects of the inherent photocatalytic activity exhibited by ZnO. This paper reports our recent study on the possibility of reducing the photoactivity of ZnO nanoparticles via surface modification and impurity doping. It was found that the photoactivity was drastically reduced by SiO2-coatings that were applied to ZnO quantum dots using the Stöber method and a microemulsion technique. The effect of transition metal doping on the photoactivity was also studied using mechanochemical processing and a co-precipitation method. Cobalt doping reduced the photoactivity, while manganese doping led to mixed results, possibly due to the difference in the location of dopant ions derived from the difference in the synthesis methods.

UV protection performance of textiles affected by fiber cross-sectional shape

Abstract
In this study, a model was set up for simulating the effects of varying fiber cross-sectional shapes on ultraviolet protection of fibers. The fiber diameter and fiber type were also involved in the model setting. Experiments of diffuse reflectance spectra measurement on natural (wool, cotton, silk), regenerated (bamboo viscose) and synthetic (polyester, nylon) fibers were conducted to verify the model predicted results. When a more complex shape was assumed as the fiber cross-section for model calculation, the predicted results have a better agreement with the actual results. The effects on ultraviolet absorption from fibers with different cross-sectional shapes were investigated at a single fiber, fiber bundle and yarn levels. With the same material, when the fiber cross-sectional area and the areal coverage of a single fiber were constant, the triangular shape had the lowest ultraviolet transmittance and the highest ultraviolet reflectance for a single fiber and also for a fiber bundle. The difference of fiber cross-sectional shapes was also significant in the ultraviolet protection of a single yarn.

Nanoparticle coatings for UV protective textiles

As the intensity of UV radiation increases every year, effective methods to block UV rays to protect human skin, plastics, timber and other polymer materials are urgently sought. Textiles serve as important materials for UV protection in many applications. The utilisation of nanoparticles to textile materials has been the object of several studies aimed at producing finished fabrics with different performances. This article reviews the recent advancement in the field of UV blocking textiles and fibers that are functionalised with nanostructured surface coatings. Different types of UV blocking agents are discussed and various examples of UV blocking textiles utilising ZnO and TiO₂ are presented. Future challenges such as wash-fastness and photocatalysis are also discussed.

The influence of yarn parameters on the ultraviolet protection of yarns

 Improving ultraviolet (UV) protection of textiles is essential to protect wearers against UV radiation induced risks. In addition to fabric parameters, yarn parameters are important factors affecting UV protection of textiles. This work is to examine the influence of yarn parameters on UV protection in order to set up a statistical model for predicting the UV protection of yarns. Wool yarns with different variables were used to test the ultraviolet protection factor (UPF) values for data analysis and the model verification. The model provides the optimized parameters for the UV protective fabric design. This work is helpful as a pre-cursor to the development of a more advanced optical model, which will look at understanding the penetration of UV light through fibres, yarns and fabrics.

Effects of fibre parameters on the ultraviolet protection of fibre assemblies

Ultraviolet (UV) radiation protection is becoming increasingly necessary for human health, and textiles play an important role. The interaction between UV light and textiles is a complex one, involving fibre, yarn and fabric parameters. In this study, an optical model is presented for examining the influences of fibre parameters on the UV protection offered by a bundle of fibres with a given mass. The effects of mean fibre diameter and fibre type on UV absorption were examined. The model was verified with results of UV–visible diffuse reflectance measurements on natural and synthetic fibres. When the mass of fibres was kept constant, within the measurement range in this study, a bundle of fibres with coarser fibres had a lower UV reflectance than that with finer ones. The model accurately predicted factors influencing UV protection, including fibre diameter, fibre transmittance, porosity and refractive index.

Preventing wool photoyellowing with inorganic UV absorbers

 Novel nano-structured inorganic UV absorbers have been fabricated in this work to protect wool against wool photoyellowing. These inorganic UV absorbers also can be used in other field for UV protection.

Research on the influence of yarn parameters on the ultraviolet protection of yarns

Considering both the yarn parameters and the light interaction (reflectance and transmittance) between two adjacent yarns, an optical model was presented to understand the ultraviolet (UV) light penetrating a single undyed yarn and a lot of yarns. The optical model was verified with results of diffuse reflectance spectra measurement on wool yarn samples. This optical model was used to predict the factors influencing UV protection, including fibre diameter, yarn linear density, yarn twist, transmittance index and refractive index. The statistical predictive model was also set up to show the relationship between the yarn parameters and the UV protection (UPF values) of the yarns. Yarns with the fine diameter, large yarn linear density and low yarn twist had the high UV protection.

UV interactions with fibres and fibrous structures

 In this research, the effects of fibre, yarn and fabric parameters on the UV protective properties were studied, and the results were interpreted by various developed models. An optimised knitted fabric for a lightweight spring/summer application with high UV protection and good thermal comfort was proposed from this systematic investigation.

Protection of silica-coated ZnO nanoparticles on pre-dyed polyester fabrics against photofading

This work was designed to investigate the ability of silica-coated ZnO (ZnO&SiO2) nanoparticles (NPs) as ultraviolet (UV) absorbers for protecting pre-dyed polyester fabrics against photofading. Despite that ZnO NPs are excellent UV absorbers, their strong photocatalytic activity limits the application in UV protection. In this study, a silica layer was coated onto ZnO NPs to form a physical barrier between the ZnO and a polyester substrate, which allowed effective UV shielding while minimising the harmful effects of photocatalytic activity on the substrate. The structure and optical proprieties of ZnO&SiO2 NPs were observed. The bare ZnO and ZnO&SiO2 NPs were, respectively, applied to polyester fabrics coloured with three kinds of dyes by a dip coating method. The photofading level of treated fabrics after exposure under simulated sunlight was evaluated. The ZnO&SiO2 NPs exhibited excellent protection on pre-dyed polyester fabrics against photofading.

Bamboo fibres and their unique properties

This paper collates the different properties of bamboo fibres as claimed by bamboo fibre and product manufacturers. The available information suggests that bamboo fibres have unique properties such as excellent appearance and feel, natural antibacterial, UV-shielding and moisture-controlling characteristics. Hence bamboo fibres provide a very promising alternative to other natural fibres by virtue of their novel properties. However, those properties may largely depend on the manufacturing process, which is not widely disclosed. Moreover, common manufacturing process may require the use of a large amount of chemicals and hence further process development may be required in order to make the product truly eco-friendly. It is identified that the data of those unique properties rarely appear in scientific journals and the validity of those claims can be speculative. Therefore, there is a strong need for non-biased scientific research and evaluation on the unique properties of bamboo fibres.