BOPP/SiO_x And BOPP/SiO_x/TiO_x Composite Membrane Preparation And Its Properties Thereafter

Organic/inorganic composite films are of increasing importance because they bear not only the properties of organic material, also have the characteristics of inorganic materials. The thickness of inorganic coating on the organic substrate has an important influence on the performance of composite films. This paper studies the factors which impact the thickness of inorganic coating on the organic substrate and the relationship with the performance of composite membrane.The effects of the process parameters, such as the concentration of tetraethoxysilane (TEOS), the sol time, the spin-coating speed, spin-coating time and the ratio of the commercial silica-gel to TEOS (Mixing Si-Sol), on the thickness of SiOx layer of the BOPP/SiOx composite films were investigated in detail. The thickness of the deposited SiOx layer could be controlled within the range of 80 nm to 1.67μm. The SiOx layer showed no observable crack or pinhole in the cross-section and vertical views by SEM and could not be peeled off with the 3M Scotch adhesive tape. The mean roughness of the SiOx layer is about 2.1 nm of 1.67μm SiOx BOPP/Si-Sol composite film and about 2.6 nm of 1.02μm SiOx BOPP/Mixing Si-Sol composite films by AFM. The water contact angles decreased to about 23.0°for the BOPP/Si-Sol composite film with 1.67μm SiOx and about 4.0°for the BOPP/Mixing Si-Sol composite film with 1.02μm SiOx. Compared to BOPP, the light transparency of the BOPP/Si-Sol composite films decreased about 5.5% with the SiOx layer from about 80 nm to 1.67μm and 7.0% for the BOPP/Mixing Si-Sol composite film with the SiOx layer from about 350 nm to 1.02μm respectively.The dip-coating method was used to prepare BOPP/SiOx/TiOx composite films. When the thickness of SiOx and TiOx coating respectively is 600 nm and 135 nm, the flexibility of composite films is unchanged. Moreover, the water contact angles decrease from 109°to 5°with the time of irradiation ultraviolet increasing to 70 min, the degradation rate of methyl orange increase to 84.1% as the time of irradiation ultraviolet increasing to 60 min. So the BOPP/SiOx/TiOx composite films have the properties of changing from hydrophobicity to superhydrophilicity and photocatalysis under the irradiation of ultraviolet.