While cross-linked polyethylene (XLPE) and linear polyethylene (HDPE) have similar names, there’s a big difference between the two. When you purchase your next chemical storage tank, it’s very important to understand the difference between these materials.
Research findings have generally supported the superior performance of cross-linked resins over linear. However, there has also been a recent trend of new sales claims touting the superiority of linear polyethylene in chemical storage applications. So, should you choose cross-linked polyethylene or linear polyethylene tanks?
It’s true that the performance of linear resins has improved and more linear-resin parts are being produced due to lower price. But a comparative performance of the two resins continues to support the scientific community’s long-held conclusion: cross-linked resins are superior to linear resins in the properties that matter most for long-term chemical storage tanks.
Cross-linked polyethylene is high-density polyethylene that is manufactured by adding a catalyst to the thermoplastic resin, which turns it into a thermoset. The catalyst causes covalent bonds that link the molecules together. Picture a chain-link fence where the metal links are actually bonded or welded together.
The result is a plastic that possesses impact resistance, tensile strength and resistance to fracture that linear polyethylene can’t match. These qualities make cross-linked polyethylene an excellent choice when tank integrity is critical. The chemical resistance, heat resistance, and dimensional stability are unparalleled.
High-Density Linear Polyethylene
In general, there are many types of linear polyethylene (high-density, low-density, etc.). Depending on the nature of a product, different materials may be used in its manufacturing. For instance, small toys may be constructed with linear polyethylene.
New linear resins have good UV resistance. In some cases, they can even rival the resistance of cross-linked resins. As a result of the new UV resistance packages used in both resins, the life expectancy of both is extended.
XLPE vs. HDPE: A Quick Comparison
The three most important factors of high-density linear tanks and cross-linked tanks include:
- Environmental stress crack resistance/notch sensitivity
- Long-term hydrostatic strength
In all three of these areas, factual measurements show cross-linked resins are much safer and more durable than linear resins. However, linear materials are less expensive than cross-linked, and can be sold cheaper as a finished product.
So, Which Should You Choose?
If price is the only deciding factor for your purchase of a polyethylene storage tank, a small linear resin tank might be a possible option. But if performance, safety, and long-term properties are important for your application, your hands-down best choice is cross-linked polyethylene tanks.
Short-term and long-term tests continue to not only reaffirm the superiority of cross-linked materials, but also show that linear materials have serious deficiencies in product performance and processing reliability. This trend is an alarming one, because it suggests that the safety and long-term performance of the products will be compromised.
When we look at overall costs, we need to look at the useful life of the tank as one of the main values that crosslinked polyethylene provides. Tanks are only a small portion of the cost of the tank system. Other costs are shipping, installing, plumbing, etc. The costs associated with replacing a tank in many cases far outweigh the cost of the tank itself. Longevity, employee safety, and peace of mind are just three values that the robust crosslinked polyethylene brings to the end user.