Application of rutile and anatase onto cotton fabric and their effect on the NIR reflection/surface temperature of the fabric

NIR irradiation accounts for 52% of the solar irradiance energy reaching the earth, most of which is transferred to thermal energy. This work was undertaken in order to investigate the possibility of applying NIR reflective coatings on cotton fabric with the purpose of surface temperature reduction when irradiated with solar light. Commercial titania was modified by means of calcination treatments. Phase transition from anatase to rutile and growth in particle size were induced, and both processes resulted in an increase of NIR reflectance of the calcined TiO₂. Irregular-shaped TiO₂ particles with sizes of 293-618 nm were obtained. The highest solar reflectance occurred in the TiO₂ sample with an anatase:rutile ratio of 35:65 and a particle diameter of 563 nm. By applying the NIR reflective coating consisting of calcined TiO₂ on cotton fabric, a lower surface temperature was recorded with a maximum difference of 3.9°C. It was found that a chitosan-TiO₂ coating could provide a better wash fastness than TiO₂ alone.