Two films, is heated to elastic plastic polymer, and also forces the polymer (molecule chains and accumulation units) along the direction of mechanical process and the vertically stretched in the direction, and then cooling of polymer thin films prepared. Main resin making films suitable for bidirectional stretch method: polyester, polystyrene, polypropylene, polyamide and polyimide films, in the polyvinyl chloride is also used in the production of biaxially oriented film in West Germany, later being replaced by other varieties. Two films are widely used in packaging, electronics, agricultural, architectural and household goods and other fields.
With the development of market demand, such as degradation of the environmental requirements of the drive, with the development of synthetic resins and its modified, with the development of two technologies, in addition to other than these synthetic resins, polyethylene and PLA, two industrial-scale processing has been the progressive introduction of material.
Two films development began in China in 1972, is meant to meet the needs of electrical and electronic industries and even military purposes. Because the two films in the strength and mechanical strength, insulation capacity, are far greater than the blown film performance. After the reform and opening, beginning in 1982, China entered a period of rapid growth in the two films.