Brightener / optical whitener is a kind of organic compounds that can improve the whiteness of fiber fabrics and paper. Also known as optical brightener and fluorescent brightener. Fabrics are often yellow due to color impurities. In the past, chemical bleaching was used to decolorize and whitening agent was added to the products. Its function is to transform the invisible ultraviolet radiation absorbed by the product into purple blue fluorescent radiation, complement each other with the original yellow radiation into white light, and improve the whiteness of the product under sunlight. Whitening agents have been widely used in textile, papermaking, washing powder, soap, rubber, plastics, pigments and paints.
According to the chemical structure, plastic brighteners can be divided into two categories: ① coumarin type, with the basic structure of coumarin ketone, which is used in celluloid and PVC plastics and has strong blue fluorescence; ② Benzoxynitrogen type, used in PVC, polystyrene and other plastics, with red fluorescence.