Geomembranes, in particular, are challenging to choose correctly. Other geosynthetics feature obvious visual differences, but almost all geomembranes tend to be either black or white, smooth, and solid. Often the amount of reflection and specific surface texture is the only visible difference between various products. Yet the construction and material makeup of the geomembrane varies greatly from product to product. Choosing a membrane at random can leave you chasing leaks and dealing with cracks that form from wrinkles. Make sure you’re selecting the best geomembrane for your liner with these helpful hints.
Woven vs Non-Woven
Almost all geomembranes are extruded and non-woven to avoid small openings that would let water flow through. Geotextiles are often woven, which is one easy way to tell the difference between these two geosynthetics. A woven or even matted fibrous material will almost never offer enough impermeability to qualify as a geomembrane liner, especially for ponds and related structures. If water containment or vapor blocking is a secondary or primary goal, stick with a non-woven product. Woven geomembranes are too permeable to function well for these purposes.
Polyethylene (PE) and Reinforced Polyethylene (RPE)
Various forms of polyethylene tend to offer the best results when used for making geomembranes. High density polyethylene (HDPE) is commonly used, but it’s often too thick and inflexible for demanding lining applications. Low density polyethylene (LDPE) offers better flexibility, but at the cost of durability and strength. Reinforced polyethylene (RPE) from BTL Liners offers the best of both materials by combining them into a single impermeable sheet. The addition of a reinforcement mesh boosts tear resistance dramatically. RPE is also chemical resistant, comes in food and fish safe formulations, and is thinner than other materials used for geomembranes without sacrificing strength. This makes it the easiest liner material to install on large commercial projects.
Polyvinyl Chloride (PVC)
PVC is one of the most widely available polymers used for geomembranes. It’s a highly flexible and relatively strong material, but it still has many downsides when used specifically as a liner. First, it’s not very chemical resistant. If the liner is installed in an exposed design, PVC tends to break down faster than other polymers due to weathering and UV degradation. It’s also prone to becoming damaged by both high and low temperature extremes, making it a poor choice for lining roadways in practically any climate. Finally, PVC seams are also trickier to seal on site than RPE and other polyethylene products. Getting tight seams is essential for a leak-proof pond or containment area, so avoid PVC for these projects.
Polypropylene geomembranes, often marked as fPP since there are rigid forms as well, are not as widely used as PVC or RPE liners. This material is easily fabricated in large sizes in the factory to reduce seams. However, this feature is balanced out by the material’s weakness towards chlorine and other chemical additives in water. It’s particularly reactive to hydrocarbons, making it a poor choice for lining refinery and mining holding and processing ponds. fPP is generally only used for ponds and some roadway projects, and it’s not even the best choice for these uses in most cases.
Chlorosulfonated Polyethylene (CSPE)
CSPE is a modern, rubber polymer formula designed to overcome many of the limitations of PVC and other materials. It’s specifically designed to resist damage from chemical reactions and corrosive mixtures, allowing it to directly contain hazardous compounds over years without breaking down. This material is also highly resistant to damage from ozone and sunlight, making it a good choice for exposed installation.
Yet, it also has many drawbacks that make it a poor choice for demanding projects. First, oils and solvents still react with the material to break it down. Second, it can’t handle extreme temperatures very well. Third, installers can only thermally weld the seams on the material when it’s still freshly manufactured. After an aging period, specific to the particular formula, the material becomes resistant to thermal welding. Since this is both the fastest and most reliable method for on-site assembly, installation of CSPE is far more difficult than with RPE liners. This greatly limits its applications in real world situations.
Polyester is not as commonly used for impermeable geomembranes as the materials listed above. Yet it is still used at times, in conjunction with thicker geotextiles, as a finished layer on top for a smoother surface. If a ribbed or dotted geomembrane needs a barrier to prevent sediment from filling in its drainage surface, a thin layer of polyester liner may be used to separate the soil. Polyester breaks down more quickly than other materials, especially when installed in an exposed way, so it’s best avoided except for temporary stabilization purposes. This material is more versatile in a geotextile form than as an impermeable geomembrane.
Polyurethane was once the most widely used geomembrane material, but it’s largely fallen out of favor for more modern polymers. It’s also unique in its ability to offer spray installation. Installers spray a thick layer of liquid PUR polymer over a fabric backing to conform exactly to the shape of the ground. While this was once necessary for some projects, today’s flexible RPE liners can offer nearly as much conformity without the extra labor for installation. Each of the benefits of polyurethane, such as chemical resistance or good flexibility, is matched or exceeded by the features of RPE liners. Unless you’re planning a highly reactive chemical storage project that specifies polyurethane as the only option, consider RPE instead for a wider range of exposed installation options.
Now that you’ve explored the various materials used for geomembranes, you should find it easier to narrow down your choices. BTL Liners offers many RPE options for all of your project needs. If you’d like to learn more about the specific polymers and reinforcement methods behind our ArmorPro geomembranes, contact us today with any questions.