We discuss the latest in polymer composite technology for storing strong oxidative chemicals like Sodium Hypochlorite, Hydrochloric Acid, and Sulfuric Acid.
Poly Processing Company commonly uses high-density crosslinked polyethylene in our chemical storage tank construction. Some medium density linear polyethylene, however, offers some advantages when storing corrosive chemicals. We use an engineered medium density polyethylene called OR-1000 to line the inside of our crosslinked polyethylene tanks for heavy oxidizing chemicals, ensuring durable construction AND an excellent antioxidant layer.
Let's look at OR-1000 and linear polyethylene to explain why in some cases one is much better suited than the other.
What is Linear PE?
Linear polyethylene is a type of plastic used in some storage tank construction. The density of the polyethylene is based on the length of the polymer chain and how tightly the polymers are packed together (branching) . This is important when it comes to how the different types of polyethylene are used.
Low Density Polyethylene (LDPE) has the most branching. This causes the low density to have a less compact molecular structure which is what makes it less dense. It is generally used for plastic bags, plastic wrap, and snap-on lids, etc.
High Density Polyethylene (HDPE) has minimal branching of its’ polymer chains. Because it is denser it is more rigid and less permeable than the LDPE. (HDPE) is used in things like milk jugs, plastic toys, and non critical tank applications.
Medium Density Polyethylene (MDPE) falls in the middle of the two. (MDPE) has a little less branching than the HDPE. It is less notch sensitive than HDPE and has better stress cracking resistance. MDPE plays an important role in Poly Processing’s anti-oxidant, engineered storage tank material called OR-1000.
How Linear PE and OR-1000 Differ
PPC has an exclusive product called OR-1000 that allows tanks to hold up against aggressive oxidation. Certain chemicals, like sodium hypochlorite, sulfuric acid, and hydrochloric acid, produce these oxidative effects.
OR-1000 can more than double the life of your storage tank in instances where you are storing an oxidizing chemical. It is made of MDPE and formulated to resist the chemical oxidation. OR-1000 addresses the oxidizing chemicals for 15 to 20 years after the tank is made.
The difference between linear polyethylene and OR-1000 is important when considering the size of a storage tank combined with the chemical that is being stored. Larger storage tanks need to be built for the specific material being stored. Some materials might not be strong enough to hold a particular material because as the tank is filled, it may begin to bulge. Some chemicals, because of the way they might attack the tank material, require an antioxidant barrier that protects the tanks integrity.
Linear polyethylene might be fine for some materials and smaller tanks, but when safety and longevity are necessary the OR-1000 is crucial in the tank design.
XLPE Provides Greater Tank Integrity
Crosslinked Polyethylene (XLPE) is high density polyethylene which has covalent bonds between connecting its polymer chains. These bonds are created via a catalyst which is heat activated during the molding of the tank and help to form 3-dimensional polymers with high molecular weights. These bonds tie the polymers together and lengthen the polymer chains giving it better physical properties. The molecular structure that is formed by crosslinking provides superior stress cracking resistance, improved toughness, stiffness, and chemical resistance compared to the HDPE.
This makes crosslinked polyethylene the best material choice for tank manufacturers. Combining the impact-resistant XLPE and the oxidation-resistant OR-1000 inner liner gives you the best of both worlds for chemical storage.
At the end of the day, linear polyethylene is not usually the right answer. In most cases it’s the less expensive answer. Safe chemical storage begins with understanding the chemical you're storing. Large volumes of oxidative chemicals can cause harm to the environment and possibly personnel if improperly stored. Poly Processing Company will engineer the best tank system for your specific application including the best polyethylene materials available today.