| People have been paying attention to the subject about photo-aging of fabric. The light protection method by indirect light absorption has been widely studied and applied, but indirect light absorption method is not suitable for all fabric, because the light absorbed, UV light in particular, will always cause the damage to the fabric. So the indirect light absorption method is only suitable for good light-fastness fabric. The direct light reflection method can fundamentally solve the issue about light-fastness of fabric, but very little related research in this area. The application of the direct reflection light protection method to light-fastness of fabric was studied in this article.In this paper, the nano-material aqueous suspensions were characterized by means of viscosity, sedimentation volume experiment, nano particles size distribution. The influence of pH value, type and content of dispersants, super shear instrument, and ultrasonic dispersion on the stability of nano-material aqueous suspensions were discussed. The best result can be realized when the super shear instruments with 1500r/min for 30min and ultrasonic dispersions for 10 min, 5wt% nano SiO_x aqueous suspensions and the sodium hexametaphosphateused as dispersant (2%of nano SiO_x in mass), pH =10. By means of particle size analyzer, the results show the particle size of most nano particles in dispersion without standing is about 190nm, and the particle size of most nano particles with standing for 12 hours is about 195nm, thus the dispersion system is very stable.Nano SiO_x with high reflectivity in the UV, visible, near-infrared band was selected. Through padding process, high reflectivity fabric was prepared and the stability of its protective function has been studied. The difference of mechanical and optical propertie of cotton fabrics before and after treated in the range of 240-2600nm was discussed. The cotton fabrics before and after treated were investigated through the accelerated aging tests with fluorescent ultraviolet aging device, and their light resistance performances were comparatively analysized. (1) Impact of nano SiO_x coating on the optical and mechanical properties of cotton fabrics.After treated by nano SiO_x through padding process, the cotton fabric's reflectance increased with absorbance little increase, therefore the transmittance became lower and the UPF values increased and UV-shielding performance markedly improved. The improvement effect of padding process on reflectance of cotton fabric is the most obvious in ultraviolet region, second in visible light region, the smallest in near-infrared region. At the same time, the strength and toughness of treated cotton fabric increased because of the strong combination between nano SiO_x and cotton fabric.(2) The photo-aging results of original and treated fabrics and their differenceThe reflectance of original and treated fabric in the range of 200-2600nm decreased with UV exposure time and absorbance changed little, which resulted in higher transmittance and the UPF values and protection performance decreased with time. The effect of ultraviolet exposure on cotton fabrics before and after treated was the most obvious in ultraviolet region , second in visible light region ,the smallest in near-infrared region. Under the same UV exposure condition, compared with original cotton fabric, reflectivity rates of the cotton fabric with nano SiO_x padding treatment were higher and transmittance was lower. As the crystallinity of cotton fabric after light aging decreased, strength of fabric reduced. Under the same UV exposure condition, strength loss rate of treated fabric was less than original fabric. |
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