UV protection finishing methods
UV protection finishing methods
5.1 Mechanism of anti-UV radiation finishing of textiles
The mechanism of anti-ultraviolet radiation finishing of textiles is to apply a substance on textiles that can reflect ultraviolet rays or selectively absorb ultraviolet rays, and can convert energy into heat or other harmless low-energy radiation to release or consume energy. The textiles after applying these substances have no adverse effects on the wearability of the fabrics and meet the usage requirements. They can also increase the reflection and scattering of ultraviolet rays by the fabrics and prevent them from penetrating the fabrics. It has the properties of heatstroke prevention, heat insulation and cool touch. From an optical principle, when light hits an object, part of it is reflected on the surface, part is absorbed by the object, and the rest passes through the object. However, when light hits a fabric that has been treated to prevent ultraviolet radiation, the ultraviolet shielding agent on the fabric either reflects the ultraviolet rays, or selectively absorbs and converts its energy into low energy and releases it, thus blocking the ultraviolet rays, while another small Partially penetrates the fabric through gaps in the fabric.
5.2 Anti-UV radiation finishing process
5.2.1 High temperature and high pressure desorption method
Ultraviolet shielding finishing of polyester, nylon and other synthetic fiber fabrics can be carried out in the same bath as high-temperature and high-pressure dyeing with disperse dyes. At this time, the ultraviolet absorber molecules are dissolved into the fiber. All you need to do is choose the appropriate ultraviolet absorber.
5.2.2 Normal pressure exhaustion method
For some water-soluble absorbents to treat wool, silk, cotton and nylon textiles, they only need to be treated in their aqueous solution under normal pressure, similar to water-soluble dye dyeing. Some absorbers can also be used in the same bath as the dye for one-bath dyeing and finishing processing.
5.2.3 Padding method
Since most UV shielding agents are insoluble in water and lack affinity for natural fibers such as cotton and linen, the exhaust method cannot be used. Instead, the shielding agent is fixed on the surface of the fabric (fiber) by bathing it with resin (or adhesive). . Padding fluid consists of UV shielding agent, resin, softener, etc. However, after dry heat treatment, the holes on the fabric are easily covered by resin (adhesive), which will affect the style, water absorption and breathability of the finished fabric.
5.2.4 Coating method
Generally, an appropriate amount of UV shielding agent is added to the coating agent, and the surface of the fabric is coated with an applicator (such as a suspended scraper, rotary screen, etc.), and then after drying and necessary heat treatment, a thin film is formed on the surface of the fabric. Although this type of method affects the wash fastness and hand feel, it has wide applicability to fiber types, low processing cost, and low requirements for application technology and equipment [4]. Most of the UV shielding agents used in the coating method are highly refractive inorganic compounds, and their UV absorption effect is related to their particle size. 2.3 Factors affecting the anti-UV radiation function of textiles The general rules of anti-UV radiation performance of textiles: short fiber fabrics are better than filament fabrics; processed silk products are better than chemical fiber raw silk products; fine fiber fabrics are better than coarse fiber fabrics; flat and special-shaped fabrics Chemical fiber fabrics are better than circular cross-section chemical fiber fabrics; woven fabrics are better than knitted fabrics. Fabric structure determines the geometry of the fabric and its porous structure. Fabric structure includes thickness, tightness, etc. A tight structure requires a large number of warp and weft yarns, a large coverage factor, low UV transmittance, and a large protective effect. The coverage coefficient of the scrim is low, the light is not easily blocked, and its protective effect is small. The UV protection factor (UPF) increases with the density of the fabric.
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