Extrusion Sheet
Sheet extrusion is a technique used for making flat plastic sheets from a variety of resins either in a roll form or as cut sheets. The thinner gauges are thermoformed into packaging applications such as drink cups, deli containers, produce trays, baby wipe containers and margarine tubs. Another market segment uses thick sheet for industrial and recreational applications like truck bed liners, pallets, automotive dunnage, playground equipment and boats. The third primary use for extruded sheet is in geomembranes, where flat sheet is welded into large containment systems for mining applications and municipal waste disposal.
During the extrusion of polymeric materials, as the material exits the flat sheet die, the required cooling is achieved by the action of pulling the molten sheet onto a specific set of cooling rolls that are generally three or four in number. These cooling rolls are also called calender or “chill” rolls and have chilled water circulating inside them to take heat out of the extruded sheet. Additionally the rolls also determine the sheet thickness along with surface texture. This is done especially in the case of structured rolls; i.e. levant, smooth, haircell, etc). Commonly, co-extrusion is used for applying one or more layers for acquiring various specific properties like soft touch or "grip", UV-absorption, matte surface or energy reflection.
