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. Common examples are roll roofing, packaging films, flexible printing plates, filtration membranes, agricultural films and tarps, frozen dinner trays (thermoformed from sheet), building insulation, kitchen

countertops, battery separators, various sheets for electronics applica-

tions, interior and exterior panels for automobiles, photographic and x-ray

films, etc. As with most extrusion equipment used in the pharmaceutical indus-

try, the sheet and film processing machinery is almost all derived from units designed for processing plastics. Even though many of the pharmaceutical

applications will be new, this has a real benefit in that the machine designs are well proven from 40 years or so of fine-tuning these devices for plastics processes. One problem that may arise, however, is that most pharmaceu-

tical sheets and films will typically be much narrower in a transverse direction than high-volume plastic products. The most common application

of sheet/film downstream equipment is for product packaging for medical and pharmaceutical products. Another application is for transdermal drug

delivery systems where an active ingredient is intimately mixed with a

Most melt extrusion systems are generally thought of as having an imaginary

separation line, immediately after the extruder (where the extrudate will

emerge from the die). 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 will deal primarily with the downstream section.