Polymer extrusion is the process of shaping unprocessed polymers into
usable products. "Polymer" is the technical term for some of the
building blocks of many organic compounds; a few examples of biopolymers
are proteins and nucleic acids. Although the extensive variety of
polymers in existence includes many of the essential components of
living things, the word polymer is often used in reference to plastic or
elastomeric materials (rubber is an example of an elastomer).
When the words "polymer" and "extrusion" are paired together, the word "polymer" always refers to a plastic or elastomeric material. The polymers that can be extruded have become essential to industry and commerce as well as to the consumer products markets. Weatherstripping
and rubber trim
and rubber tubes
and a very wide variety of other plastic and elastomeric shapes
are formed using the extrusion process. Construction companies install them in plumbing systems. Automobile manufacturers affix use them to insulate vehicles. Extrusions can be found in homes, restaurants, offices, schools and in many other settings. Their presence has become ubiquitous across industry and commerce.
The extrusion process is highly standardized and is almost the same for plastic and rubber materials. Differences relating to operating temperature and other similar considerations may apply, but the same basic principles apply to all extrusion processes. At the beginning of the extrusion process, a stock of raw plastic or elastomeric material is collected in a suspended hopper. The hopper is positioned above a conveyance channel, and the hopper releases its contents into the channel. A long shearing screw in the conveyance channel forces the raw material down the channel as it turns. The friction caused by the turning screw causes the material to become heated to its melting point. In some cases, additional electric heating elements are added to the channel to aid in the heating process. A die, which is a tool used to shape raw materials, is positioned at the end of the conveyance channel. In the case of polymer extrusion, a die is a specially-designed hole in a metal plate. When the molten raw materials are forced through the die, they take its shape, emerging on the other side as newly extruded products. They can then be cut and prepared for shipment or sent for additional processing.