Specific qualities of strength, reactivity, and transparency differ between varieties of plastic materials, varying the types of plastic tubes produced. Acrylic tubing, for example, is fairly durable, inexpensively manufactured and is often near-transparent. Polyvinyl carbonate (PVC) is often opaque and is widely used in plumbing applications for that reason, though it can be engineered to be near-transparent.
Many other varieties of plastic are used to create tubing. High and low density polyethylene (HDPE and LDPE), polypropylene, polystyrene, PET, nylon, ABS and polyurethane are just a few examples. Major consumers of plastic tubing products include the healthcare products industry, heating and cooling products and services industries, municipalities, laboratories, home and garden products manufacturers, pool supply companies, petrochemical processing operations and farms.
Plastic tubing is so widely used because of the versatility, easy manufacturing and relative low cost of plastic products compared to other materials. Glass tubing, for example, is heavier, more easily broken and more expensive.
There are several processes by which plastic tubing can be produced, but the most efficient method is plastic extrusion. Plastic extrusion is a thermoforming process; thermoforming involves heating a plastic and forming it. At the beginning of the extrusion process, a collection of raw plastic material, which is called stock, is gathered in a hopper. The hopper is placed above a conveyance channel into which the stock is released. Within the channel a large screw turns and moves the stock toward a die.
Dies are specially designed shapes that form raw materials into usable products; a die for plastic tube extrusion is a plate with a hole and pin through which molten plastic is forced. The turning of the screw in the conveyance channel creates friction that, combined with heat generated by heating elements along the channel, causes the plastic to become molten.
At that point, the molten plastic is forced through the hole in the die, taking that shape. When the plastic emerges on the other side of the die, it becomes a tube. It is allowed to cool and harden, at which point it can be cut to length and prepared for shipment or sent for further processing like labeling or painting.