Preparation and properties of hydrophobic-hydrophilic switchable coating via UV irradiation on cotton fabric

SiO2/TiO2 composite sol was prepared with tetraethoxysilane(TEOS) and tetrabutyl titanate(TBT),and was coated on cotton fabric to present hydrophobic-hydrophilic switchable property via UV response.The contact angle of the coated fabric was 121.3° and was hydrophobic,but after being irradiated in UV for 18 h,the contact angle was 0° and was hydrophilic.When the fabric being irradiated and then kept in dark place for 12 h,the contact angle was increased to 93.2° from 0°.After ten cycles of being UV irradiated and then heeping in dark place,the contact angle of the fabric was kept in between 0° and 92°-96°,showing hydrophobic-hydrophilic switchable property.The ultraviolet spectrum analysis showed that the ultraviolet irradiation transmittances of the coated fabrics were decreased slightly via irradiation UV for 18 h,whereas,the ultraviolet irradiation transmittances were increased when the radiated fabric was kept in dark place for 12 h,and this change of the ultraviolet radiation transmittances verified the mechanism of switchable wettability.