Preparation and application of melamine-formaldehyde photochromic microcapsules

Melamine-formaldehyde microcapsules encapsulating photochromic compounds with particle size less than 5 μm had been prepared by in situ polymerization, and their application in textile was also studied. The Fourier transform infrared spectroscopy (FTIR), biological microscope and laser particle analyzer were utilized to characterize the structure, morphology, size and size distribution of melamine-formaldehyde photochromic microcapsules. The UV–visible spectrophotometer was used for monitoring the UV–vis absorption of different mass fraction of photochromic compounds in dioctyl phthalate (DOP) solvent and the kinetics and fatigue resistance of photochromic microcapsules and photochromic print cloth. As a result, the mixed photochromic solution of photochromic compound and DOP solvent appeared maximum absorption peak in a certain wavelength range after exposed in a mercury lamp (375 W) for 10 min when the mass ratio was 2%. The lifetime of photochromic microcapsules could extend from 6–7 h to 69–75 h under continuous UV, when stirring rate, emulsification time and mass ratio of core materials/wall materials were 1000 rpm, 5 min and 1:1, respectively. Meanwhile the photochromic painting paste had excellent water resistance, acid/alkali resistance, soaping resistance, light resistance and fatigue resistance.