Dr. Eric Richter of the Pigments & Additives Division of Clariant addresses the role of lubricants in the production of PVC film and discusses how to choose a lubricant or combination of lubricants to achieve high quality film by calendering.
Many plastics are processed at strongly elevated temperatures. These thermoplastics can be further divided into two large groups. About 85% of all thermoplastics are processed in a moderate temperature range up to about 230C; among these are the commodity plastics polyethylene, polypropylene and polyvinylchloride. The second group consists of thermoplastics that are processed at around 300C. This includes many engineering thermoplastics such as polyamides and polycarbonate. During processing, thermoplastics are exposed to these elevated temperatures for some time. The average residence time at these high temperatures is of the order of several minutes and varies depending on the processing method and the number of processing steps. In addition to residence time, contact with oxygen also has an effect, which is particularly important in calendering.