The Scientific Term: Cross-Linked Polyethylene
PEX is formally known as cross-linked polyethylene, referencing its molecular structure. The cross-linking process strengthens the polymer chains, enhancing durability. For instance, ASTM International standards classify Cross-linked Polyethylene under the chemical designation “PEX 2306” for plumbing applications.
Industry Abbreviations and Branding
In construction, Cross-linked Polyethylene is often labeled by its manufacturing method: PEX-A, PEX-B, or PEX-C. These denote peroxide, silane, or electron beam cross-linking techniques. Uponor, a leading brand, markets PEX-A as “Uponor AquaPEX” to emphasize its flexibility.
Regional and Colloquial Terms
Some regions refer to Cross-linked Polyethylene as “flex pipe” or “poly pipe.” In Australia, it’s colloquially called “plumbable poly” to distinguish it from non-potable polyethylene tubing. A 2022 Sydney plumbing code update standardized “PEX” to avoid confusion.
Historical Names in Material Science
Before its plumbing adoption, cross-linked polyethylene was termed “XLPE” in electrical and industrial contexts. A 1990s NASA study used XLPE for cable insulation, paving the way for its later use in water systems.
Comparisons to Similar Polymers
Cross-linked Polyethylene is sometimes confused with HDPE (high-density polyethylene), but their cross-linking differentiates them. HDPE lacks PEX’s heat resistance, as shown in a 2021 University of Michigan test where HDPE deformed at 160°F (71°C), while PEX-B remained intact.
Building Code Designations
Building codes classify Cross-linked Polyethylene under terms like “thermoplastic tubing” or “polymer piping.” California’s 2023 Title 24 regulations list Cross-linked Polyethylene as “CSST-P” (corrugated stainless steel tubing-polymer) when used in hybrid gas systems.
Marketing Labels in Retail
Retailers often rebrand Cross-linked Polyethylene for consumer clarity. Home Depot sells it as “SharkBite Cross-linked Polyethylene,” while Lowe’s uses “PEX-B ProPEX.” These labels emphasize compatibility with push-fit fittings, simplifying DIY projects.
Standardization in Global Markets
Globally, Cross-linked Polyethylene is standardized as “EN ISO 15875” in Europe and “ASTM F876” in the U.S. These codes ensure uniformity. For example, a German manufacturer’s Cross-linked Polyethylene pipe meeting EN ISO 15875 can be sold as “PEX” in all EU markets.
