What are the plastic film forming methods?
|There are many plastic film forming methods, among which three processes of casting, extrusion and blow molding are common. Casting film is a non-stretched, non-oriented flat extruded film produced by melt flow quenching. There is no obvious orientation structure. The uniaxial stretching and biaxial stretching methods are common in the film production by extrusion, and the biaxial stretching is a production method which has been paid attention to in recent years. The basic principle of the biaxial stretching technology is that the high polymer raw material is first heated and melted into a thick sheet by an extruder, and then is subjected to a certain temperature range below the melting point above the glass transition temperature, and is then carried out in the longitudinal direction and the transverse direction by a stretching machine. The stretching of the multiples causes the molecular chains to be oriented and arranged in an order parallel to the plane of the film, and then heat-set in a tensioned state to fix the oriented macromolecular structure, and finally to form a film by cooling and subsequent treatment.|
The blown film is usually produced by extrusion blow molding, plasticizing and extruding the material, forming tube blank inflation molding, and then cooling, drawing and coiling. The blown film is oriented. The blow molding process is simple and the most common film forming process. The plastic film is formed by different methods, and the prepared film has different properties, such as film conductivity; the stretched film has higher barrier properties than the unstretched film, lower permeability to gas, optical properties, transparency and surface gloss. Improve, good dimensionality and uniform thickness.