Why does cotton wool in cotton turn yellow?

(1) Mix old bleached cotton. Old tattered cotton (so-called ancient cotton) is bleached and mixed with normal cotton to confuse the real with the fake. We should pay attention to three points in identifying it: ① color. The white color of normal cotton is natural, while the white color of bleached old cotton is false. 2 luster. Normal cotton fiber has the natural luster of waxy layer, while bleached old cotton has no luster. ③ Elasticity. Normal cotton has good hand elasticity, while bleached old cotton has poor elasticity. (2) Blended regenerated cotton. Regenerated cotton is the waste of cotton mills, cotton cloth and other things, which is regenerated by cutting and carding. Identification should also use comparative methods: ① Look at the appearance. Regenerated cotton is cotton wool, and the fiber is comfortable, but the length is very different, which is different from the natural appearance of normal cotton fiber. ② When the regenerated cotton is pulled by hand, there are long fibers in the cotton bundle, which are mixed regenerated chemical fibers. It has high strength and is not easy to break. ③ Observe cotton under ultraviolet light. If there are many colors such as yellow and blue, they are produced by chemical fibers in recycled cotton, but normal cotton does not have this color. (3) Blended cotton staple fiber. Pay attention to four points: ① Appearance. There are many small neps (white stars) in cotton mixed with cotton linters, with different fiber thicknesses and many impurities. 2 colors. The color of normal cotton fiber is white, which is different from the white of cotton linter. ③ Elasticity. After adding cotton linters, the elasticity of cotton becomes worse. (4) When the cotton bundle is pulled by hand, the fiber layer before the bundle is obviously shortened, which is inconsistent with the normal cotton fiber. (4) Identification of spraying lard and talcum powder in high-grade cotton. Smell it. This adulterated cotton smells of lard and even stinks. 2 Look at the color. Cotton is light red in white and dull. 3 rub. Rub cotton in the palm of your hands, white powder will be stained on your hands, and the caked talcum powder will fall off; Spraying lard will make your hands feel greasy. (5) Spray diesel oil into low-grade cotton and sprinkle with stone powder or sand. The method is basically the same as item (4), but the smell and color of adulterated cotton are different. Cotton wool and cotton tires, there are many suppliers, buyers and manufacturers here. This is the supply of quilts. Raw cotton ... if you can't get through to the store express, please explain in advance.