| Polyolefin films have been used widely in the food, pharmaceutical and electronic devices packaging industry because of their transparency, easy processability, low cost, and so on. However, these packaging films are permeable to oxygen, carbon dioxide, water vapor and volatile organic compounds, which affect the quality and lifetime of the products.In order to improve the barrier property of the biaxially oriented polypropylene (BOPP) film and meet the barrier demands for packaging materials, SiO2 coating, PVA/SiO2 organic-inorganic hybrid coating and CS/SiO2 organic-inorganic hybrid coating were prepared on BOPP film via sol-gel process, in our work. Tertaethoxysilane was used as the precursor. A silane-coupling agent ofγ-glycidoxypropyltrimethoxysilane (KH560) was used to improve the adhesion between the coated layer and the substrate film. In addition, absolute alcohol and hydrochloric acid were used as the co-solvent and the catalyst, respectively. Then, polyvinyl alcohol and chitosan were used as the organic compounds, respectively. As a result, three types of composite films compsosed of the coaing and the BOPP film were prepared. The structure and properties of these films were inspected. The main conclusions are as follows:For the SiO2/BOPP barrier composite films, the influences of KH560/TEOS molar ratio, absolute alcohol content , deionized water content and hydrochloric acid content were investigated on the barrier properties of the composite films by the use of orthogonal experiment and single factor experiments.As a result, the optimal technological parameters of preparation SiO2 barrier composite films had been obtained. The molar ratio of (TEOS+KH560): absolute alcohol: deionized water: hydrochloric acid was optimized at 1:4:3:1.2, and the molar ratio of KH560 to TEOS was 2:3. At the same time, oxygen and water vapor barrier properties of SiO2 composite films was 21 times and 1.7 times that of the bare BOPP film, respectively. Tensile strength, breaking elongation and the transmittance of SiO2 composite films were better than BOPP film.For the PVA/SiO2/BOPP barrier hybrid composite films, with the increase of PVA content, the oxygen barrier property of the composite films was enhanced, while the water vapor barrier property of the composite films was dropped. As the mass ratio of PVA increased to 80%, the oxygen barrier property of the composite films was 308 times that of the pure BOPP film, however, water vapor barrier character was half of the BOPP film. At the same time, tensile strength and breaking elongation was 1.4 times and 1.7 times that of the pure BOPP film, respectively. The composite films had a good transparency due to the light transmission rate of was more than 90%.For the CS/SiO2/BOPP barrier hybrid composite films, the adhesion between hybrid layer and the BOPP substrate film was satisfactory. No phase separation and no creaking were observed on the surface of the coating. With the increase of CS content, the oxygen barrier property of the composite films was enhanced firstly and then decreased, while the water vapor barrier property of the composite films was dropped. As the mass ratio of CS increased to 18%, the oxygen and water vapor barrier characters of the composite films was 112 times and 1.3 times that of pure BOPP film, respectivly. At the same time, tensile strength and breaking elongation was 1.5 times and 1.8 times that of BOPP film, respectively. Although, light transmission rate was lower than that of the BOPP film, the composite films had a good transparency.
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