ABSTRACT
One of the largest volume processes for extrusion within the plastics industry is the production of sheets and films. Many products are needed in sheet form, or at least start out as a sheet and undergo postprocessing afterward. Most melt extrusion systems are generally thought of as having an imaginary separation line, immediately after the extruder. The first half of the system (the portion with the extruder) is considered the upstream or melt processing section. The second half of the system is the downstream or takeoff section. This chapter deals primarily with the downstream section. One common pharmaceutical application using extrusion is transdermal drug delivery systems (TDDS), which are alternatives to more classic drug delivery systems such as tablets, capsules, or even injections. For making thin continuous films out of a polymer-based material, there are two main processes: blown film and cast film.
