Many things we buy or use in life have flexible packaging materials. For example, a circle of plastic paper on a beverage bottle, plastic film on items purchased in supermarkets, transparent bags covered with electronic products, etc. These things have a common name, called PVC heat shrinkable film.
Heat-shrinkable films first appeared in Germany during World War II. PVDC was used to pack weapons after bidirectional stretching to prevent rust. Therefore, the heat shrinkable film is used in industrial product packaging from the beginning of industrial production, and then the heat shrinkable film is used for food packaging.
The development of the plastic packaging film industry in China has mainly experienced more than 20 years, during which a certain scale has been formed. The heat shrinkable film industry occupies an important position in the packaging market and is also an industry that has a positive role in promoting the national economy.
1. Brief introduction of heat shrinkable film
Heat shrinkable film, commonly known as shrink film, is a film that can shrink significantly after being heated, so it can tightly wrap the article and can maintain its shape for a long time. The heat-shrinkable film is designed using the polymer molecular chain stretching and orientation principle and is formed by the method of quenching and setting. The physical principle is: when the plastic raw material is heated and plasticized and extruded into the mother film, the polymer is forcibly stretched in the longitudinal and horizontal directions between the glass transition temperature and the drilling temperature, so that the polymer molecular chain is stretched Orientation, then the polymer is rapidly cooled, and the molecular orientation is frozen. When the film is reheated to the “thaw” temperature, due to the stress relaxation caused by the movement of the molecules, the molecules return to their original state and contract.
2. Application of heat shrinkable film
Heat shrinkable film is used in the sales and transportation of various products, its main role is to stabilize, cover and protect the product. At present, the food industry is the largest application market for heat-shrinkable packaging materials. Heat shrinkable film is widely used in the packaging of various fast foods, lactic acid foods, beverages, beer cans, various alcohols, agricultural and sideline products, and local specialties. In the non-food field, the application of heat shrinkable films is also increasing, such as cosmetics, daily necessities, pharmaceutical products, electronic products, toys, building materials, handicrafts, etc.