Pulp fibers always appear yellow to grayish white, which is caused by the absorption of purple and blue light with wavelengths of 0.4-0.5 um by the lignin contained in the pulp fibers. The higher the lignin content in the pulp, the darker the color. Grinded wood pulp contains more lignin, which appears light yellow. Fluorescent brighteners can be added to improve whiteness. Today, we will learn about the whitening principle of fluorescent brighteners and the factors that affect their whitening effect

Fluorescent whitening agent whitening principle

Fluorescent whitening agent, also known as optical whitening agent. Fluorescent whitening agent is adsorbed by fibers and fixed on paper. Under light, the whitening agent can reflect visible light and absorb ultraviolet light from invisible sunlight, and convert it into visible light, emitting fluorescence of different intensities and colors from the paper. When ultraviolet light stops shining, this purple or blue fluorescence quickly stops emitting