【Secret】Blowing method of heat shrinkable film

Heat shrinkable film is a kind of thermoplastic film that is stretched and oriented in the longitudinal and transverse directions of the film during the production process, and shrinks by heat during use. The heat shrinkability of the film has been applied as early as 1936. At the beginning, the rubber film was mainly used to shrink and package foods that are not easy to preserve. Nowadays, heat-shrinking technology has been developed to almost use plastic shrink film to package various commodities, and it has a wide range of applications in the fields of food and beverage, electronic products, automotive supplies, daily chemicals, stationery, and medicine. The blown film method of heat shrinkable film is generally divided into single bubble method, double bubble method and triple bubble method. The ordinary blown film production process belongs to the single-bubble method. Because the film's inflation and stretching ratio in the longitudinal and transverse directions cannot be accurately controlled, and the inflation ratio is generally about 2 to 3, the thermal shrinkage rate of the film is not high, so one bubble The products produced in France are mainly used for packaging in product logistics, such as the outer packaging of beer beverages and daily electronic products. The double bubble method is mainly used in the production of POF film. Since the film is inflated twice, the stretching ratio of the film in the longitudinal and transverse directions can be controlled, and the stretching ratio is high. Through the control of the process formula, the shrinkage rate of the film can reach more than 70%. The main application areas of POF film are in some small packaging products. With the application of heat shrinkable film in food, especially cold fresh meat, the production process of three-bubble heat shrinkable film came into being. Because fresh meat products require high thermal shrinkage stability of film packaging, low thermal shrinkage temperature, and good barrier performance, ordinary double bubble method cannot produce products that meet the requirements. The three-bubble method can solve this problem. The previous one: What are the main advantages of heat shrinkable bags? Next: How to identify the quality of heat shrinkable film