Photochromic performance optimization of polyurethane microcapsules by interfacial polymerization method

Abstract

Spiropyran photochromic materials have been widely studied in military camouflage, optical data storage, information encryption, and fashion ornaments. The non‐photochromism and low endurance of solid spiropyran make the challenges of their application. Photochromic microcapsules with a butyl acetate solution of spiropyran as core and polyurethane as shell are synthesized via interfacial polymerization. The optimized polyurethane photochromic microcapsules are prepared with a Tween 20 concentration of 4 wt%, core–shell ratio of 16:5, and spiropyran concentration of 0.40 wt%. Polyurethane photochromic microcapsules with a mean particle diameter of 0.33 μm are obtained. The morphology shows smooth spheres, and the core–shell structure is observed. Butyl acetate in the microcapsule core does not evaporate at a temperature lower than 218.01°C as the microcapsule shell insulates heat. The polyurethane photochromic microcapsules are mixed with adhesive, thickener, and water into a paste and screen‐printed on cotton fabric. The printed fabric shows the ΔE of 17.56, 11.93, and 6.96 after 80s irradiation with the xenon lamp intensity of 102, 68, and 34 mW cm−2. The light stability of the photochromic fabric is excellent as ΔE decreases about 8.28% after 20 cycles of UV‐Vis irradiation.