Whitening agents, commonly known as white dyes, are colorless organic compounds that can stimulate fluorescence under ultraviolet light irradiation. They can improve the whiteness and luster of substances. Whitening effect is the use of optical complementary color principles to make yellowing substances treated with fluorescent whitening agents not only reflect visible light, but also absorb ultraviolet light outside of visible light and transform it into visible light with purple blue or cyan color for reflection. Yellow and blue complement each other, offsetting the original yellow color of the substance and making it appear pure white.
According to chemical structure, it can be divided into five categories:
1. Styrene type, used in industries such as cotton fiber and certain synthetic fibers, papermaking, soap making, etc., with blue fluorescence;
2. Coumarin type, with a basic structure of coumarinone, used in celluloid, polyvinyl chloride plastics, etc., with strong blue fluorescence;
3. Pyrazoline type, used for fibers such as wool, polyamide, and acrylic, with green fluorescence;
4. Benzoxynitrogen type, used for fibers such as acrylic and plastics such as polyvinyl chloride and polystyrene, with red fluorescence;
5. Phthalimide type, used for fibers such as polyester, acrylic, and nylon, with blue fluorescence.
Whitening agents are mainly used in textiles, papermaking, plastics, coatings, detergents, printing inks, waxes, packaging materials, etc. Whitening agents are only optical brightening and color compensation, and cannot replace chemical bleaching. Therefore, if the colored material is treated directly with a whitening agent without bleaching, it cannot fundamentally achieve a whitening effect, and attention should be paid when using it.
Post time: Sep-01-2023