There are many kinds of synthetic polymers, and many of them are plastics like PVC. The defining characteristic of PVC is its versatility.
Raw PVC, depending on its specific properties and the method by which it is formed, can be made into any shape and can feature varying qualities of rigidity, flexibility, clarity or opaqueness.
In the case of rigid PVC, it can be extruded into a limitless variety of strips, tubes and profiles. Extruded PVC pipes are among the most widely used plumbing materials in the world. Flexible PVC can also be extruded into tubing, which is used in food processing, wastewater treatment and in many other applications.
Flexible and rigid PVC can be manufactured to be almost completely transparent or completely opaque, making it ideal for use in some chemical processing applications. Like all plastic varieties, PVC resists corrosion from exposures to some chemicals better than others, and some studies suggest that PVC products can leach toxins into their contents.
For this reason, careful consideration should be given to the application of a PVC product before it is employed.
The PVC extrusion process is very similar to that of other plastic extrusion processes. Some differences of operating temperature and duration may apply, but the basic concept of extrusion remains the same regardless of materials.
PVC extrusion begins with the collection of raw PVC stock in a hopper suspended above a conveyance channel. The PVC is released from the hopper into the channel, and a long shearing screw forces the PVC down the channel as it turns. At the end of the channel is a die, which is a tool that shapes raw materials into usable products.
In the case of plastic extrusion, a die is a metal plate with a specially-designed hole. The PVC can be forced through that hole once it becomes molten. The turning of the shearing screw combined with heat generated from electric heating elements causes the PVC to melt by the time it reaches the die. The molten PVC is then forced through the die, and it takes its shape.
When it emerges on the other side of the die, it is newly extruded PVC. The extrusion is then allowed to cool; it can then be cut to length and shipped or prepared for additional processing.