High-Density Cross-Linked Polyethylene (XLHDPE), commonly referred to as Cross-Linked Polyethylene (XLPE), is a type of polyethylene characterized by a unique molecular structure. The cross-linking process creates bonds between polymer chains, significantly enhancing the material’s properties. This results in a highly durable, heat-resistant, and stress-crack-resistant material, making it ideal for various applications, particularly in chemical storage.
We Take Pride in Our Process: At Assmann, we believe your tank is more than just storage. It’s an asset that keeps your business running as usual. That’s why we make every tank with durability top-of-mind, which starts with molding our tanks at a cooler temperature than the industry standard. While other manufacturers mold their tanks at high heat, >600 °F, we make ours at a temperature range of 450-550 °F. That allows us to create uniform wall thickness across the surface, which results in a more durable tank.
Additionally, this controlled process enables us to exceed the 60% GEL requirement established under ASTM D 1998 standards. Greater GEL content means improved material bonding and enhanced long-term performance. Going even further, our tanks are gradually cooled, decreasing the mold temperature incrementally, which allows for a better cure of the plastic. Air cooling also gives the benefit of not shocking the polymer during the cooling phase, reinforcing integrity in the quality of the XLPE material. This combination of these three unique processing techniques adds longevity to every product we manufacture.
Key Advantages of XLHDPE: One of the primary benefits of XLHDPE is its superior heat resistance. Unlike other polyethylene variants, the cross-linked structure allows XLHDPE to maintain its integrity and performance even under high-temperature conditions. This makes it an excellent choice for chemical storage, especially during the hot summer months when temperatures can reach extreme levels.
What Can You Store in XLPE? Cross-linked polyethylene (XLPE) is a highly durable type of plastic resin. It can safely store a variety of
chemicals:
- Acetic Acid (80%)
- Aluminum Chlorohydrate (100%)
- Aluminum Sulfate (50%)
- Calcium Carbonate (100%)
- Calcium Chloride (30%)
- Chlorine Dioxide (38%)
- Citric Acid (100%)
- Copper Sulfate (25%)
- Ferric Chloride (50%)
- Ferric Sulfate (60%)
- Ferrous Chloride (37%)
- Ferrous Sulfate (25-30%)
- Hydrochloric Acid (37%)
- Hydrofluoric Acid (52%)
- Hydrofluorosilicic Acid (30%)
- Hydrogen Peroxide (10%)
- Liquid Ammonium Sulfate (45%)
- Magnesium Chloride (35%)
- Methyl Alcohol (100%)
- Peracetic Acid (30%)
- Phosphoric Acid (50-75%)
- Poly Aluminum Chloride (100%)
- Polyorthophosphate (100%)
- Potassium Hydroxide (50%)
- Potassium Permanganate (4%)
- Sodium Aluminate (100%)
- Sodium Bisulfite (40%)
- Sodium Carbonate (85%)
- Sodium Chloride (26%)
- Sodium Chlorite (34%)
- Sodium Hydroxide (50%)
- Sodium Hypochlorite (15%)
- Sodium Permanganate (40%)
- Sodium Silicate (100%)
- Zinc Orthophosphate (100%)
Temperature considerations for different chemicals vary. Some chemicals are freeze sensitive and can crystallize or freeze even in temperatures well above 32°F—and in some cases, certain chemicals can crystallize around 50°F. The heat of strong oxidizing chemicals should be a consideration because higher temperatures can accelerate the chemical decomposition, and extreme temperatures can cause tanks to weaken. It is best to store chemicals at room temperature unless otherwise recommended by the supplier.
Comparing XLHDPE with Other Tank Materials: When considering materials for chemical storage tanks, several options are available, each with its own set of advantages and disadvantages:
- Polyethylene (PE)
- Pros: Cost-effective, lightweight, and resistant to many chemicals.
- Cons: Limited heat resistance and prone to stress cracking under prolonged exposure to harsh conditions.
- Polypropylene (PP)
- Pros: Higher temperature resistance than PE, good chemical resistance.
- Cons: Very difficult to mold over 36″ diameter, requiring fabrication for larger sizes. This fabrication can lead to a significant number of welds, which may fail over time. The process is also labor-intensive, increasing costs.
- Stainless Steel (316 SS)
- Pros: Excellent durability, high heat and chemical resistance.
- Cons: Expensive, heavy, and requires maintenance to prevent corrosion. Also, longer lead times and much higher costs compared to polyethylene.
- Fiberglass Reinforced Plastic (FRP)
- Pros: Good chemical and heat resistance, customizable shapes and sizes.
- Cons: Higher cost and potential for micro-cracks leading to leaks. Also, much longer lead times and higher costs.
Why Choose XLHDPE as a Solution?: Choosing XLHDPE for chemical storage offers several compelling advantages:
- Durability: The cross-linked structure provides exceptional strength and resistance to mechanical stress, ensuring a longer lifespan for storage tanks.
- Thermal Stability: XLHDPE can withstand high temperatures without deforming or losing its properties, making it ideal for summer storage conditions.
- Stress Crack Resistance: The material’s resilience to stress cracking ensures safe and reliable storage, reducing the risk of leaks or failures.
- Chemical Resistance: XLHDPE is compatible with a wide range of chemicals, making it a versatile choice for various industrial applications.
FAQs:
- What does XLPE stand for? XLPE stands for cross-linked polyethylene, a thermoset resin used specifically for chemical storage.
- What is the difference between XLPE and HDPE? XLPE is a modified form of High-Density Polyethylene (HDPE). Crosslink has higher impact resistance than Linear polyethylene, and due to its molecular structure, it is less apt to catastrophically fail.
- Can XLPE tanks be used outdoors? Yes, cross-linked polyethylene storage tanks can be stored outdoors.
- How long do XLPE tanks last? The average life expectancy of an Assmann cross-linked polyethylene tank is 15-20 years or even longer,
depending upon a variety of factors, such as which chemical is stored and the use of proper ventilation. - What temperatures can XLPE withstand? The maximum operating temperature that XLPE can withstand is roughly 140°F. At this temperature, you are nearing the softening point of the polymer. Assmann recommends that you keep your storage tank as close to ambient temperature as possible.
- Is XLPE food-grade/FDA approved? No, cross-linked polyethylene tanks cannot be used for FDA applications. Due to the catalysts used in the rotational molding process, Crosslink polyethylene can place an odor or flavor into the materials stored. Note that Assmann’s tanks have been tested by NSF and can be used to store chemicals for municipal use.
- Can XLPE tanks be repaired if damaged? No, XLPE storage tanks cannot be welded like Linear polyethylene. Crosslink polyethylene is a thermoset plastic. Since there are so many different types of damage, if you feel your tank needs to be repaired, we would want you to contact our factory to discuss your options.
- What sizes of XLPE tanks does Assmann offer? We offer a variety of tank sizes, ranging from 20 to 12,500 gallons. We can customize your tank’s configuration to help you maximize the use of your allocated space.
- How is XLPE different from linear polyethylene? Compared to linear polyethylene, crosslinked polyethylene provides higher impact resistance, improved stress crack resistance, greater temperature tolerance, and a tougher molecular structure. Read more about the differences here.
- What chemicals are NOT compatible with XLPE? Assmann does not recommend that Crosslink polyethylene be used to store Sulfuric Acid.
Ensuring Safe and Efficient Storage Solutions: The unique properties of XLHDPE make it an optimal material for chemical storage tanks. Its durability, thermal stability, and resistance to stress cracking ensure that stored chemicals remain safe and secure, even in high-temperature environments. By choosing XLHDPE, businesses can benefit from a reliable and efficient storage solution that meets the demanding requirements of summer chemical storage.