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Analysis of Influencing Factors and Improvement Methods of Textile Color Fastness to Sunlight
The color fastness to sunlight is to measure the sunlight resistance of dyes and materials. The test method can be either sunlight exposure or sunlight aging machine exposure. The fading degree of the samples after exposure is compared with the standard color sample. There are two kinds of grading standards: wool blue label and gray card. For this reason, it can be determined whether it meets the standard requirements and what can be improved. (Hong Kong) Co., Ltd. is a manufacturer of textile testing instruments, which can provide domestic and imported sun aging Machine, welcome customers in need of timely inquiries. In addition, the influencing factors and improvement methods of textile light fastness are described below. Factors affecting the color fastness of textiles to sunlight: 1. Influence of dyes and coating structure The photofading mechanism of dyes is very complex, but the main reason is that the dyes are excited after absorbing photons, and a series of photochemical reactions occur to destroy the structure, resulting in discoloration and fading. The light fastness of textiles mainly depends on the chemical structure of the dye, as well as its aggregation state, bonding state and mixed color combination. Therefore, the rational selection of dyes is very important. 2. The influence of dyeing depth and floating color The light fastness of dyed fabrics is related to the dyeing depth. The greater the dyeing depth, the larger the aggregate particles of the dye on the fabric, the smaller the proportion of the dye per unit weight exposed to the air, and the higher the light fastness. For light-colored fabrics, the proportion of dye aggregates on the fiber is smaller, The light fastness also tends to decrease accordingly. In the factory, the light fastness grades that cannot meet the requirements are generally medium and light colors, and some light brown fabrics. After the light fastness test, the red light is almost completely lost, and the color change is more obvious. Whether the dyeing process is properly selected, and whether the washing and soaping are thorough after dyeing, will affect the amount of unfixed dyes and hydrolyzed dyes present on the fabric, that is, the amount of floating color. The light fastness of the floating color is obviously lower than that of the fixed reactive dyes. Therefore, improper treatment after dyeing will also affect the light fastness of the fabric. 3. Influence of fixing agent and softener The use of fixing agent greatly improves the rubbing fastness, washing fastness and staining fastness of reactive dyes. Generally, the washing fastness of fabrics treated with cationic low-molecular or polyamine fixatives is in the 4-5 grade, but the light fastness of fabrics fixed by such fixatives has decreased. Soft finishing of cotton fabrics with cationic softener will reduce the light fastness of reactive dyes, mainly because the softener will turn yellow after being exposed to the sun, so that the color of the fabric will also change. How to improve the light fastness of textiles: 1. Selection of dyes or coatings In terms of improving light fastness to light, the choice of dyes or coatings is the key. For a single color, try to choose a dye with higher light fastness. For the dyed fabrics that need color matching, the light fastness grades of the dyes of each component should be the same. The poor light fastness of one component will affect the light fastness of the entire mixed color. Dyes with a relatively small content in the mixed color component can choose a dye with a high level of light fastness to ensure the overall color fastness of the fabric. 2. Improvement of soaping process In the dyeing process, a reasonable dyeing process should be formulated, fully soaped and washed, and the amount of hydrolyzed dyes and floating colors should be minimized to improve the light fastness of the fabric; Color fastness to rubbing, etc. 3. Selection of fixatives and softeners Most fixatives are quaternary ammonium salts, sulfonium salts or phosphorus salts. Such fixatives and dyes form lakes on the fibers. Although the washing fastness is very good, it often reduces the original light fastness of the dyes. Therefore, when the light fastness requirements are high, try to avoid using this type of fixing agent. Some cationic softeners and amino-modified silicone softeners bring a plump hand to the fabric, but also have disadvantages such as yellowing, discoloration of dyes, and inhibition of fluorescent whitening agents. 4. Ultraviolet absorber and light fastness enhancer If the processing conditions of dyed fabrics have been fixed, such as dyeing, fixing, softening and other steps have been completed, under these conditions to improve the light fastness of dyed fabrics, you can choose sun exposure Fastness enhancers or UV absorbers. Such additives can directly absorb the ultraviolet rays irradiated on the fabric and prevent the dyes from being damaged by photo-oxidation.
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