The main methods for preparing polyethylene films are as follows:
1. Blown film extrusion: Blown film extrusion is a commonly used method for preparing polyethylene films. . In this process, molten polyethylene resin is extruded through a cylindrical die, expanded into a film under the action of high-pressure gas, then solidified by cooling, and finally rolled into a roll. This method can prepare various types of polyethylene films such as low-density polyethylene (LDPE), high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE).
2. Cast film extrusion: Calendering is another commonly used polyethylene film preparation method. In this process, molten polyethylene resin is extruded through a flat die and then cooled and solidified on cooling rollers to form a film. Finally, the film is wound into a roll through a winding device. Compared with blow molding, films prepared by calendering have better flatness and thickness uniformity.
3. Solution casting: In this method, the polyethylene resin is first dissolved in a suitable solvent to form a solution. Next, the solution is poured onto a flat substrate, and the solvent is evaporated in an environment of constant temperature and humidity to form a thin film. This method can prepare polyethylene films with special properties, but the recycling and treatment of solvents need to consider the environmental impact.
These methods can be selected based on specific application needs and material properties. In the actual production process, blow molding and calendering are the two most commonly used methods for preparing polyethylene films.