Plastic is heated and then passed through the rollers under high pressure, which then results in an increase in temperature. The material will be degraded if this temperature becomes too high.
The thickness of the film produced is dependent on the gap between the rollers. The width of the rollers dictates the size of the film.
This process is used predominantly with PVC but can be used to produce films for the agricultural industry using PS and ABS. It gives a lower cost option to extrusion.