Preparation and properties of super hydrophobic films from siloxane-modified two-component waterborne polyurethane and hydrophobic nano SiO2

Nanocomposite films with super hydrophobic surface were prepared by building rough micro/nano structure on the surface of siloxane-modified two-component waterborne polyurethane (2K-WPU) with hydrophobic nano SiO2. Firstly, nano SiO2 prepared by StOber method with tetraethoxysilane (TEOS) as precursor was modified with trimethylethoxysilane (TMES), in order to cover a layer of hydrophobic methyl groups on the surface of nano SiO2. Then, a series of nanocomposite films with different water contact angles were obtained by adding different contents of TMES modified SiO2 into the siloxane-modified 2K-WPU. The effects of the content of nano SiO2 on the morphology and hydrophobicity of film surface were investigated. The results showed that the surface structures of the nanocomposite films became rougher and the water contact angle of nanocomposite films was increased obviously with the increase of the content of hydrophobic nano SiO2. Super hydrophobic nanocomposite film with water contact angle over 150 degrees was successfully fabricated by using polysiloxane as low surface energy material and hydrophobic nano SiO2 as micro/nano rough structure builder on the polymer surface. Moreover, incorporating nano SiO2 into the 2K-WPU matrix could increase the glass transition temperature and thermal stability of the nanocomposite films.