Don't be fooled, then understand 'that layer of film'1

1. The definition of flexible packaging film is in the national packaging general term (GB4122—83), the definition of flexible packaging is: flexible packaging refers to the packaging that can change the shape of the container after filling or removing the contents. Various bags, boxes, sleeves, packages, etc. made of paper, aluminum foil, fiber, plastic film and their composites are all flexible packaging. Generally, sheet-like plastics with a thickness of 0.25 mm or less are called films. The plastic film is transparent, flexible, has good water resistance, moisture resistance and gas barrier properties, good mechanical strength, stable chemical properties, oil resistance, easy to print exquisite pictures and texts, and can be heat-sealed to make bags. It can meet the packaging requirements of various items, and is an ideal material for packaging convenience foods that are easy to store and put away, daily necessities, and small packaged goods in supermarkets. Flexible packaging printing based on plastic film occupies an important position in packaging printing. According to statistics, since 1980, plastic packaging in some advanced countries in the world has accounted for 32.5% to 44% of the entire packaging printing. Generally speaking, because the protection of a single film material to the contents is not ideal, a composite film that combines two or more films into one layer is often used to meet the requirements of food preservation and aseptic packaging technology. The outer layer materials of the composite film are mostly made of materials that are not easy to scratch, sand, have excellent optical properties and good printing properties, such as: paper, cellophane, stretched polypropylene, polyester, etc.; the middle layer is a barrier polymer, such as : Non-toxic, odorless polyethylene and other thermoplastic resins are mostly used for aluminum foil, vapor-deposited aluminum, and polytetrafluoroethylene.