PEX Tube - means cross-linked polyethylene radiant heat tubing

Uponor first introduced the world to PEX tubing.

Uponor first introduced the world to crosslinked polyethylene (PEX) tubing in the early 1970s. With more than 30 years of service — longer than any other PEX manufacturer in North America — Uponor PEX is the fastest-growing choice for residential and commercial plumbing systems, thanks to its powerful, inherent advantages over metallic and rigid-plastic piping.

PEX is an acronym for crosslinked polyethylene. Polyethylene is the raw material and the X refers to the crosslinking of the polyethylene across its molecular chains.

  Features of Uponor Pex A Tubing:

• Smallest bend radius  
• Tested and proven for over 30 years  
• Wirsbo PEX is the most flexible tubing and the least likely to kink  
• Maintenance free  
• Highest degree of crosslinking 

 PEX RADIANT HEATING, PLUMBING AND FIRE PROTECTION SYSTEMS

Three Decades of PEX - 8 pages, The story about Uponor's development of cross linked polyethylene 

Link to Related Document on Uponor / Wirsbo PEX:

Advantages of Wirsbo PEX A Tubing

PEX-a Tubing- Why It's Better 

Currently, three methods for producing crosslinked polyethylene (PEX) tubing exist.

• Engel or peroxide method (PEX-a)

• Silane method (PEX-b)

• E-beam (electron beam) or radiation method (PEX-c)

All three processes generate tubing that is crosslinked to varyingdegrees, and are acceptable for potable water distribution applications according to ASTM F876 and F877 standards.

Engel Method (PEX-a)

Uponor manufactures Engel-method PEX-a tubing. The PEX tubing industry considers this tubing superior because the crosslinking is done during the manufacturing process when polyethylene is in its amorphic state (above the crystalline melting point). Because of this, the degree of crosslinking reaches around 85%, resulting in a more uniform product with no weak links in the molecular chain.

Silane Method (PEX-b)

PEX-b tubing is crosslinked after the extrusion process by placing the tubing in a hot water bath or steam sauna. The degree of crosslinking for PEX-b is typically around 65 to 70%. This method is not as evenly crosslinked as the PEX-a method, nor does it have the same degree of thermal memory, which allows kinked tubing to be reshaped  with the use of a heat gun.

E-beam Method (PEX-c)

PEX-c uses an electron beam to change the molecular structure of the tubing (i.e., crosslink) after the extrusion process. The PEX-c method requires multiple passes under the beam to reach a 70 to 75% degree of crosslinking. Side effects of this process are discoloration due to oxidation (from natural white to yellow, unless other pigment is added), and a slightly stiffer product.

PEX-a Distinctions

The properties in PEX-a tubing make it the most flexible PEX on the market. This allows the tubing the tightest bend radius available — as little as 3 flexibility also greatly reduces the instance of kinked tubing. However, if there is the rare occurrence of kinked tubing, that’s okay, because PEX-a tubing has thermal memory. This allows the repair of kinked tubing with a simple shot of heat from a heat gun.

The shape memory of PEX-a tubing offers the unique opportunity for fitting connections. Shape memory allows PEX-a tubing to expand and then shrink back to normal size, creating strong, durable and reliable fitting connections. And finally, PEX-a tubing offers the greatest resistance to crack propagation (how a crack grows) over PEX-b and PEX-c tubing. This means if a crack occurs in PEX-a tubing, it is least likely to grow over time and cause leaks or damage.

Uponor Tubing

With over 30 years of service — longer than any other PEX manufacturer in North America — Uponor is the leader in PEX tubing for radiant heating, plumbing and fire protection systems. More than 2 billion feet of Uponor PEX tubing is in service in North America alone, and over 12 billion feet of tubing is installed worldwide. With that kind of history, you can count on Uponor PEX to offer the highest-quality tubing for all your application needs.

• Non-Barrier Tubing (54)