How is PVC Pipe Made?

Chemical Reaction

• PVC has its origins in the chemical gas referred to as vinyl chloride. When vinyl chloride is exposed to sunlight a chemical reaction occurs. The reaction is known as polymerization, which transmutes into a whitish solid material. To achieve the shape and solidity of a PVC pipe, a series of chemicals are introduced to one another. Natural gas is heated to create ethylene. The process is referred to as cracking. Later, sodium chloride (found in the form of rock salt) is spliced using electrolysis. As a result chlorine and lye (sodium hydroxide) is produced.

Molecular bonding

• Chlorine and ethylene (natural gas heated under pressure) are introduced to make vinyl chloride monomer (VCM). The molecules are bonded from each molecule's end. The result is a long chain of polyvinyl chloride polymer. In essence, plastic is created. The polymerized plastic, called thermoplastic PVC powder (which is compounded), melted and molded into piping. The result is a tube of PVC plastic. As a result of the chemical process (PVC becomes very solid and rigid), PVC is less likely to break during earthquakes. It can withstand pressures that many metals (such as copper piping) cannot tolerate. This is why PVC is the preferred material for plumbing and underground wiring.

Manufacturing

• As small as 16 mm and as large as 630 mm tubing/pipes are manufactured using a machine called an extruder. PVC plastic is routed through a double screw stem extruder (conical twin screw) or a parallel double screw extruder. Molding determines the wall thickness of the PVC hose. The diameter of the pipe is made by the PVC pipe extruder (The standard is 1/2 to 24 inches in diameter). The production speed of the standard PVC pipe extruder is about 20 meters per minute. The PVC hose runs through a vacuum pump. A ring cutting machine is employed at the end of the assembly line to divide the PVC tubing into sections of individual pipes. The individual pipes are cooled and racked. After inspection, the completed PVC pipes are sent to the warehouse for final inspection, labeling and shipping.