What is PEX?

PEX is a kind of tubing made from crosslinked HDPE or high density polyethylene. The "PE" stands for polyethylene and the "X" for cross-linked, hence the acronym PEX. There are three different methods of making PEX:

  1. PEX-A is produced by the peroxide (Engel) method. This method performs "hot" cross-linking, above the crystal melting point. However, the process takes slightly longer than the other two methods as the polymer has to be kept at high temperature and pressure for long periods during the extrusion process. The cross-linked bonds are between carbon atoms
  2. PEX-B (PE-Xb, PEXb). The silane method, also called the "moisture cure" method, results in PEX-B. In this method, cross-linking is performed in a secondary post-extrusion process, producing cross-links between a cross-linking agent. The process is accelerated with heat and moisture.
  3. PEX-C (PE-Xc, PEXc). PEX-C is produced through electron beam processing, in a "cold" cross-linking process (below the crystal melting point). It is the cleanest, most environmentally friendly method of the three, since it does not involve other chemicals and uses only high-energy electrons to split the carbon-hydrogen bonds and facilitate cross-linking

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