Synthesis, properties and application in polyvinyl butyral of spirooxazine photochromic compounds

Abstract

Purpose The purpose of this paper is to evaluate the effect of antioxidant 2,6-di-tert-butyl-p-methylphenol (BHT) on the thermal stability and fatigue resistance of spirooxazine and then study the properties of photochromic polyvinyl butyral resin (PVB) films. Design/methodology/approach BHT was introduced into the spirooxazine system by blending and covalent bonding. The properties of spirooxazine solutions and photochromic PVB films were studied. Findings The thermal stability and fatigue resistance of spirooxazine covalently linked (BHT-SO) or mixed (BHT/SO) with BHT were higher than the system without BHT, and BHT-SO was the better one. But acidic substance would greatly impair the fatigue resistance of spirooxazine. The optimum addition amount of BHT-SO2 to PVB was 2.5 per cent, and the minimum limit was 0.01 per cent. The fading kinetic and fatigue resistance of film were similar to the solution and better. Plasticizer could accelerate the fading rate and strengthen the mechanical properties of photochromic film but had no effect on the fatigue resistance. Research limitations/implications Spirooxazine could be grafted onto the PVB chain to make the ring closure fading reaction slower. Practical implications In addition to the wide application prospects of photochromic materials in decoration, optical storage, etc., the photochromic PVB film in the car safety glass can absorb sunlight and turn blue, then fade to colorless when the sunlight disappears, making the interior environment more comfortable. Originality/value The introduction of BHT into the spirooxazine system not only exerts its ability to capture free radicals, but its bulky volume also increases the resistance of the ring closure, making the fading process slower.