High-density polyethylene (HDPE) liners are multifunctional products that serve as an impermeability layer for various applications. One of the core benefits of HDPE liners is that some of their features can be modified by changing the thickness of the liner, which typically ranges from 30 to 120 mil. The thickness of the liner will affect features like permeability, strength, weight, roll length, flexibility, and cost. For most projects, the thickness of the liner is selected during the planning stages and depends on the stresses that will be affecting the liner (1).
While HDPE liner thickness specifications can variety significantly, 40 mil is among the most commonly used options. In this article, we will provide an overview of 40 mil HDPE liners and explore applications these liners are well-suited to tackle.
Typical properties of a 40 mil high-density polyethylene liner
Most HDPE liners will retain their chemical properties regardless of their thickness. In other words, a 40 mil liner will have as much corrosion resistance as similar liners of varying thickness. However, there are some aspects of the liner that will change as the thickness changes. For example, the liner’s overall strength and puncture resistance will decrease with its thickness. A liner’s permeability is also proportional to its thickness. Therefore, a 60 mil HDPE liner will be less permeable than a 40 mil liner—about 50% less permeable, in fact.
There are many benefits to a thinner liner though. For instance, a 40 mil HDPE liner is less expensive and will also have a lower transportation per square foot of lined area. The 40 mil HDPE liner is also easier to install because it will have a longer roll length, which reduces the number of seams installers will need to weld.
The best applications of a 40 mil HDPE liner
The 40 mil HDPE liner offers a good balance of strength, impermeability, and cost. These liners are used for a variety of applications such as potable and reserve water as well as containment, agricultural, and dairy ponds. At 40 mil, the liner will offer an average tensile strength (ASTM D6693) of 15 kN/m, tear resistance (ASTM 1004) of 133 N, and puncture resistance (ASTM D4833) of 356 N.
An application growing in popularity is to use an HDPE liner in the construction of a covered biogas capturing pond on dairy farms. These specialized ponds use HDPE liners for the containment system (the pond lining) and for the cover system (gas capture). Covered containment ponds used for biogas capture require less land than uncovered ponds and typically provide higher and more consistent biogas production. The smaller land footprint makes these ponds more economical than alternative digesters.
For uncovered pond uses, an HDPE liner can be used to line evaporation ponds found in a number of industries such as salt production, waste disposal for desalination plants, mining, and agriculture. For each of these applications, the 40 mil HDPE serves to support the containment layer to prevent the contents from leaching out into the surrounding environment. For specialized applications, the liner can be furthered customized during manufacturing to support design or quality control requirements.
Sourcing high-quality 40 mil HDPE liners
Manufacturers like AGRU America offer the ability to combine a 40 mil HDPE liner with other geosynthetic products for added functionality. AGRU can extrude liners with asperities to enhance shear strength or studs to allow for fluid flow and eliminate the need for a separate net and/or geocomposite. The liner can also be manufactured with a special conductive bottom layer, which allows for spark testing (ASTM D7240). A conductive lined 40 mil HDPE liner can be used for Construction Quality Assurance Testing for possible holes, punctures, tears, cuts, cracks, and similar breaches over the area during installation or for ongoing monitoring of containment ponds.
- Topliff, CR, “Uses and Installation of HDPE Liner to Reduce Soil Erosion and Prevent Water Loss.” West Texas A&M. (2018). Accessed on June 2019. https://wtamu-ir.tdl.org/handle/11310/153.