Polyethylene tubing, also known as poly tubing, is used in a very broad range of industrial, commercial and consumer products contexts.
Polyethylene is a versatile plastic and can be used to make tubing with walls as thin as soda bottles, or it can be used to make thick, break and crack-resistant tubing. It can be used in soda machines, municipal water systems, drainage systems, petrochemical processes and many more applications.
The range of applications for which polyethylene tubing is used calls for an equally wide range of polyethylene varieties. The two main varieties are high and low-density polyethylene (HDPE and LDPE). High-density polyethylene is characterized by its thickness, strength and durability; it is used in the transportation of high-volumes of liquids or pressurized gasses.
It is resistant to impact and can be corrosion-resistant. Low-density polyethylene is characterized by flexibility as opposed to HDPE’s rigidity. LDPE is more suitable in applications in which the tubing is moved frequently or is attached to equipment that is mobile.
Polyethylene, like all varieties of thermoplastics, can be fabricated through any one of several thermoforming processes. The most common method of plastic tubing fabrication is plastic extrusion. Plastic extrusion is the process by which a stock of raw plastic materials is melted, forced through a die and turned into a usable plastic product.
The extrusion process begins with a collection of stock (raw plastic material) in a hopper suspended above a conveyance channel. The stock is directed into the conveyance channel, within which a long, turning screw pressurizes and moves the stock as it turns. As the stock progresses through the channel, the turning of the screw causes friction, which heats the stock. By the time it reaches the die, the combination of the friction and heat from electric heating elements along the channel causes the stock to melt.
The die, which is a tool used for shape a raw material, is in the case of plastic tubing a large plate with a hole and pin; the molten stock is forced through the hole and emerges on the other side of the die as a newly extruded plastic tube. Once shaped, the new tubing is allowed to cool and harden. It is then cut to length and prepared for shipment or additional processing.