Development of bopp film with high barrier properties to be used in packaging industry

Biaxially oriented polypropylene (BOPP) film is a transparent, durable, easily processed and stretchable film. It is one of the most widely used polymeric materials in food packaging due to its properties such as high tensile strength, optical transmittance, chemical and dimensional stability. The main problem with BOPP film is lack of moisture and oxygen permeability as in all polymeric packaging, in other words, lack of barrier properties. Extending shelf life of food is directly with the oxygen and moisture permeability properties of the films used in packaging. For this reason, the film surface is coated with aluminum metal or different polymeric material to improve the barrier properties of BOPP films. Pasteurization and sterilization are heat treatment method applied in the food industry to purify nutrients from microorganisms. Shelf life of foods is extended with pasteurization and sterilization process. The packaging of pasteurized/sterilized foodstuffs before packaging requires an extra process and the risk of contamination is extremely high. Compared to the films used in other packaging, polymeric films to be used in the pasteurization/sterilization process in the package have some additional advantages such as visual integrity, gas permeability, physical durability, non-migrating of food package components into the food and resistance to hot processing, as well as resistance against cold for pasteurized/sterilized foodstuffs stored in chilled cabinet. The aim of this study is to develop BOPP films with improved barrier properties, can be used in the sterilization and pasteurization processes of food packages. In the first stage of the study, a sol-gel coated film surface was obtained by applying different ratios of TEOS/water/ethanol mixtures on the standard commercially used BOPP film. During this study, 20 μm and 30 µm film thicknesses were used and the optimum film thickness to be used during the study was determined. In addition, TEOS/water/ethanol ratios were studied as 5/1/6, 4/1/6, 3/1/6, 2/1/6 and 1/1/6 to determine the optimum mixing ratio in the study. During coating process, using a commercially used film applicator, the sol-gel mixture was applied to the film surface at the ratios specified above. 2 drops of NH3 were applied to the mixture as a catalyst. The obtained coatings were first kept at room temperature for 5 minutes and then cured at 120 °C for 30 seconds. Coated film structures were characterized using different instrumental techniques. Oxygen, moisture and gas permeability properties of ormoser coated BOPP films were determined as well as their gloss, haze, and optical transmittance properties. Keywords: BOPP film, Polypropylene, Sol-Gel Chemistry, Sol-Gel coating