3/8" PEXLock PEX Crimp Ring 3PK

SafePEX PEXa Pipe with Black Print Stream.

What Exactly is Crosslinked Polyethylene (PEX)?

Crosslinked polyethylene is polyethylene (PE) which has undergone a change in molecular structure whereby the polymer chains are chemically linked, crosslinked (X), with each other to form a three-dimensional network. The result is a flexible thermoset1 polymer with improved mechanical, thermal and chemical properties.

The Commercial Crosslinking Process

SafePEX uses the high-pressure peroxide method of crosslinking which is also known as PEXa. This method was pioneered in 1968.

In this procedure, a very small amount of liquid peroxide is added to the base HDPE (high-density polyethylene) pellets, in a controlled mixing chamber at moderate temperature. Next, through a combination of high temperature and pressure developed within the extrusion machine, crosslinking occurs as the resulting compound is melted and extruded as crosslinked pipe. The peroxide is consumed in the reaction. The high-pressure peroxide method allows for a higher degree of crosslinking as compared to other methods. SafePEX PEXa pipe is typically 80 to 85% crosslinked.

Similar to a Chain-Link Fence

Like a chain-link fence, PEX will expand with excessive pressure and then return to its original shape when the pressure is removed – so PEX pipe will usually allow the expansion of water that freezes inside when it has room to expand evenly along its length. Non-crosslinked pipe is rigid. It may resist higher pressure before initial expansion, but once it does deform and expand, it is forever changed and weakened.