2021 年 19 巻 p. 1-8
A near-infrared (NIR) reflector in cotton clothes may prevents several dermatological problems. TiO2 is commonly used for the NIR reflector coating in cotton. The NIR reflectance value is expected to increase if smaller TiO2 particles were used. A simple mechanical process of ultrasonic wet-milling to reduce the TiO2 particle size is proposed in this study. The reduction process utilizes ultrasonic cavitation by an ultrasonic homogenizer has succeeded in reducing the particle size from 170 to 80 nm as indicated by particle size measurement results and as supported by transmission electron microscopy results. The wet-milling particles of 80 nm TiO2, along with 170 and 280 nm TiO2, were used to coat cotton fabrics. Optimization of the coating process was performed using citric acid and chitosan as binder agents. The effect of citric acid and chitosan was studied through NIR spectroscopy, scanning electron microscopy, and X-ray fluorescence. From the NIR spectroscopy characterization results, it is found that the fabrics which are coated with the smallest TiO2 particle size (80 nm) indeed show highest NIR reflectance among others.