Photochromic materials refer to materials with photochromic properties. Photochromism, that is, some substances will change color under the irradiation of ultraviolet light or visible light, and when the light disappears, they will change to the original color reversibly. It is also called “photochromism” or “photochromism”. Photochromic properties can be divided into reversibility and irreversibility.
The general reaction of photochromic phenomenon can be represented by AB. Under the stimulation of external light (hv), A changes its molecular structure or electronic energy level, forming compound B with different absorption spectra. B returns to compound A under the action of light (HV’) or heating with other wavelengths. Because the absorption spectrum between the two substances has changed, when the change is in the visible region, the reversible color change of hair color and achromatic color will occur, that is, photochromic phenomenon.
The most commonly used methods to combine photochromic materials with fabrics are as follows:
- Printing and dyeing technology
The color-changing materials are made into microcapsules, because some materials have no affinity for fibers, and only after being processed into microcapsules can they be fixed on fibers by adhesives; Some materials need to be protected from external factors, or only when they are enclosed in microcapsules can the discoloration effect be maintained. The so-called microencapsulation means that the color-changing compound or together with other additives (solvents, light stabilizers, etc.) is wrapped with natural or synthetic polymer or microbial film into small balls of several microns to dozens of microns through phase separation, interfacial reaction, physical method, etc., so as to avoid the influence of high temperature and other impurities and strengthen contact with other additives. - Fiber technology
Fiber technology mainly includes solution spinning and melt spinning. Solution spinning method, that is, the color-changing compound and the reagent to prevent its transfer are directly added to the spinning solution for spinning; Melt spinning method is to melt and blend the color-changing polymer with polyester, polypropylene, polyamide and other polymers. Or the color-changing compound is dispersed in a resin carrier which can be mixed with the spun polymer to make color masterbatch, and then mixed with polymers such as polyester, polypropylene and polyamide for melt spinning.
Photochromic fiber is a high-tech functional fiber with rapid development and great vitality in recent years. It has high added value and high benefit. With the continuous introduction of high technology into this field, photochromic fibers will continue to develop and improve.
With the increasing demand for high-grade and personalized clothing and functional finishing fabrics, the development of new photochromic fabrics will have a good development prospect and broad application prospects.