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                                                  Xiangcheng District, Suzhou
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                                                  Identification methods of dyes for textile...

                                                  Author: ComeFrom: Date:2018/4/8 16:14:25 Hits:2485
                                                  Color fastness is an important indicator of printing and dyeing textiles. The color fastness of different kinds of dyes is not the same. The molecular structure and chemical properties of various dyes are different to different textiles, and some dyes are chemical reactions to the textile fibers and chemical reactions. The key is combined with the textile, and some dyes are fixed on the fabric in a physical reaction. Therefore, the indicator of color fastness is not the same. The variety of dyes on textiles is difficult to be identified by the naked eye. It must be determined by chemical methods, and our current general practice is to determine the type of dye provided by the factory or the inspector, and the experience of the inspectors and the understanding of the production plant. If we don't identify the dyes in advance, it is very likely that the unqualified products will be identified as qualified products. There are many chemical methods for identifying dyes. The general procedure is relatively complex, time-consuming and laborious. Therefore, a simple identification method of dyes on cellulosic fibers in printing and dyeing textiles is introduced in this paper.
                                                  1 the principle of determining the simple identification method
                                                  According to the dyeing principle of dyestuffs on textiles, common textile components are commonly used as the following kinds of dyes: fiber - cationic dyes, polyamide and protein fibers - acid dyes, polyester and other chemical fibers - disperse dyes? Cellulose fibers - direct, vulcanized, active, raw, NaF, coatings and phthalocyanines? For blending Textiles, or interwoven fabrics, are based on the composition of the dyes, for example, for polyester and cotton blended fabrics, in which the polyester components are disperse dyes, and the cotton composition is carried out by the corresponding dyes, such as dispersion / activity, dispersion / reduction and so on. According to the dyeing theory, the main factors affecting the color fastness of textiles depend on the type of dyes used in cellulose fibers. Therefore, how to determine the types of dyes in cellulose fibers is the key.
                                                  Identification of the types of dyes on 2 cellulose fibers
                                                  2.1 sampling and preprocessing
                                                  Identification of dyes on cellulose fibers is based on sampling and sample pretreatment. When sampling, you should take the same dye part, for example, the sample contains several tones, and each color should be taken. If fiber identification is needed, we should confirm fiber types according to FZ / TO1057 standard. If the sample, which contains impurities, grease and slurry affecting the experiment, must be treated with detergent in the 60-70 15min hot water, washing and drying. If the sample is made of resin, it should be treated with the following methods.
                                                  1) urea formaldehyde resin was treated with 1% hydrochloric acid at 70-80 15min, washing and drying. 2) acrylic resin specimens can be used 50-100 times in the two step 2-3H reflow process, washing and drying out. 3) silicone resin can be treated with 5g / L soap and 5g / L sodium carbonate 90cI = 15min, washing and drying.
                                                  Identification of 2.2 direct dyes
                                                  The sample was added to lmL concentrated ammonia solution for boiling water 5 to 10mL to make the dye fully extracted.
                                                  The extracted samples were removed, and 10-30mg's white cotton cloth and 5-50mg NaCl were put into the human extract, boiled 40-80s, placed after cooling and washed. If the white cotton cloth is dyed almost the same hue as the sample, it can be concluded that the dyestuff used for the dyeing of the sample is direct dye.
                                                  Identification of 2.3 vulcanized dyes
                                                  The 100-300mg samples were placed in the 35mL test tube, adding 2 ~ 3mL water, 1-2mL10% sodium carbonate solution and 200-400mg sodium sulfide, heating and boiling 1-2min, taking out the sample of 25-50mg white cotton cloth and 10-20mg sodium chloride in the test tube. Boil 1-2min. Take out and put it on the filter paper to reoxidize it. If the color light is similar to the original sample, it can be regarded as vulcanizing or sulphur reducing dyes.
                                                  Identification of 2.4 reductive dyes
                                                  Put 100-300mg sample in 35mL test tube, add 2 -3mL water and 0.5-lmL10% sodium hydroxide solution, heat and boil, add 10-20mg insurance powder, boil 0.5-lmin, take out the sample into 25-50mg white cotton and 0-20mg NaCl, continue to boil 40-80s, and then cool to room temperature. Take out the cotton cloth and put it on the filter paper to oxidize. If oxidation is almost the same as the original color, it indicates the existence of vat dyes.
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