Cross-linked polyethylene or PEX is tube piping generally used in water supplies and has been around since the 1960s. PEX is more resistant to corrosion, chemicals, deformation and extreme temperatures than metal or plastic piping. Another advantage of PEX over other types of piping is that it's easier and faster to install since it uses less connections and fittings. It's also very flexible. PEX has been used in service lines, ice rinks and radiant heating systems, including bathroom floor heating systems.
PEX-A is created through the peroxide (Engel) method, where the cross linking between the molecules occurs at higher temperatures than what is needed to create polymer decomposition. PEX-A is the most flexible PEX tubing and can hold up against high pressure. It can be bent in nearly any direction and has very low density at 0.930. PEX-A also has the best uniformity, thermal memory and kink resistance over the other two types of PEX. While PEX is the least affordable and not available everywhere, it also lasts the longest. Brands of PEX-A include House PEX PEX-A and Safelink Mr. PEX.
PEX-B is produced through the silane (moisture cure) method, which means that the molecular cross-linking occurs after the process of creating the fixed cross-section profile (extrusion process) with the assistance of both a catalyst and contact with water. PEX-B is not very flexible and doesn't bend in many directions, but is moderately durable and has the ability to retain its shape after being heated. It's relatively kink resistant, but the ability to repair kinks reduces with exposure to heat. This type of PEX has the highest density at 0.941. Examples of PEX-B include Vanguard and RTI.
PEX-C is created by cold cross-linking, which means that the cross-linking was done by using an electron beam on the tube. The electron irradiation method basically destroys the bonds between the polymer molecules and starts the process of cross linking. PEX-C is the second-best type of PEX after PEX-A. It's more flexible and better resists kinks compared to PEX-B. It's pretty durable and has the ability to retain its shape after being heated. It's also uniform throughout. While it can resist kinks pretty well, it becomes less kink resistant and harder to repair kinks after being heated. PEX-C can be bent in more directions than PEX-B and resists coil memory better than PEX-B. PEX-C has the same density as PEX-B at 0.941. Examples of PEX-C include Embassy Industries Inc. and Stadler Inc.
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