Composite film is widely used in food packaging, such as shopping malls of fast food, frozen foods, puffed foods. All of these are made of composite film. The composite film can not only maintain the excellent characteristics of the single-layer film, but also make up for their own inadequacies. After compounding, it has new features to meet the different requirements of the products for the film. For example, food packaging requires films with excellent properties such as moisture resistance, air resistance, light resistance, oil resistance, high temperature resistance, and good heat sealability, as well as good printability and decorative art effects. Performance and requirements are difficult to achieve for a single film.
The most widely used PE film has excellent transparency, moisture resistance, heat resistance, and chemical stability, but its oil resistance, oxygen resistance, and printability are poor. PET and PA films have high tensile strength and fatigue strength, but the former has poor moisture resistance, and the latter has poor heat sealability and chemical resistance. PE (glass) has excellent transparency, no static electricity, no pollution, and easy adhesion, but its toughness, water resistance, and moisture resistance are all poor. Aluminum foil has metallic luster and thermal conductivity properties, and has good moisture, vapor, and radiation resistance. However, it has drawbacks such as easy breakage, lack of flexibility, and lack of thermal adhesiveness. Each layer of the film is compounded together, and has excellent properties such as moisture-proof, air-proof, light-proof, heat-resistant, oil-resistant, and good heat-sealing properties, and becomes an ideal packaging material.
At present, the high-grade daily PH steaming bag uses a three-layer composite film made of a plastic film as the base material. The middle layer is made of aluminum foil and is excellent in barrier properties. It is good for food storage for a long period of time. The outer layer is made of BOPP film and has excellent dimensional stability. Back gravure printing, compounded with aluminum foil with adhesive to ensure the firmness and smoothness of printing color. The inner layer uses a PE film, which uses its advantages of heat resistance, softness and easy sealing. After the combination of the three, can withstand 120 ~ C high temperature sterilization, microbes will not invade, play a role in preservation and taste.
There are many kinds of composite films. The common ones are the compounding of cellophane and plastic film, the compounding of plastic film and plastic film, the compounding of aluminum foil and plastic film, the compounding of aluminum foil, glass, paper and plastic film, various papers and their prints and There are 30 to 40 kinds of compounding of plastic films and so on, and the number of composite layers is generally 2 to 5 layers. The basic structure of various composite films is a non-thermoplastic or high-melting point film such as PT, BOPP, NY, PET, etc., as the outer layer, and PP, PE as the inner layer for comprehensive application.
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