Geomembrane Liner Materials
A geomembrane liner is a synthetic membrane used to control fluid migration in manmade projects and structures. It is often utilized as liners in landfills to prevent leakage of waste into groundwater.
It’s also used in wastewater lagoons and animal waste containment applications. It is also an ideal choice for expansive lining projects due to its durability and chemical resistance.
High Density Polyethylene (HDPE)
High Density Polyethylene (HDPE) is a popular choice for landfill liners, wastewater treatment and environmental containment projects due to its superior thermal and chemical resistance. It also resists folding damage, dynamic impact and has excellent puncture and tear strength. HDPE is a versatile material that can be incorporated into a variety of projects and can be manufactured with additives to enhance specific properties.
HDPE liners are available in both smooth and textured, and come in 30 to 100 mil thicknesses. They are delivered in substantial rolls geomembrane liner that can be heat-welded on-site using wedge or fusion welding. This makes them a cost-effective solution for expansive lining projects that require low permeability and long periods of exposure to outdoor conditions.
Aside from its exceptional chemical and UV stability, HDPE is easily installed. This is because it is a flexible liner material that can be welded with a hot air torch and inflated into place using air pressure. This method of installation allows the liner to undergo a complete cycle of thermal expansion and contraction, which ensures the integrity of the liner.
Unlike PVC and other non-HDPE liner materials, HDPE geomembrane is food safe and does not release toxic fumes during the welding process. This is a crucial characteristic for those who must meet rigorous CQA requirements on large commercial projects. Moreover, a recent study by Islam and Rowe demonstrated that HDPE geomembrane with lower MFI values has better stress cracking resistance than those with higher MFI values.
Linear Low-Density Polyethylene (LLDPE)
Linear low-density polyethylene (LLDPE) is a type of plastic used in geomembrane liners. It is a homopolymer of ethylene, with some additional longer-chain olefins incorporated to improve its performance. The most common longer-chain olefins are butene and hexene. LLDPE has a lower molecular weight distribution and outperforms LDPE in tensile strength and impact resistance. It is also often blended with LDPE to provide the best of both worlds.
A geomembrane liner is a membrane used to prevent the migration of toxic, flammable, or corrosive chemicals and waste in man-made structures. These liners are made of various materials including EPDM, High Density Polyethylene (HDPE), and Reinforced Polypropylene (RPP). Some also incorporate geotextiles for added stability and functionality.
While HDPE has become the global standard for Safe Containment applications, LLDPE is a viable option as well. However, marketing an LLDPE as an HDPE in these types of applications is not appropriate and can lead to confusion among the customer base.
HDPE is linear, while LLDPE is branched and has short side chains that interrupt crystallization. This is why it has a lower density than tightly packed crystallites of HDPE. Like other linear polymers, it is a thermoplastic and will melt and flow when exposed to heat. In contrast, nonlinear polymers are thermosets and will never melt. They may soften, but will never fully melt and flow.
Polyvinyl Chloride (PVC)
PVC is one of the most commonly used impermeable geomembrane materials. Its high tensile strength provides superior resistance to impact damage and puncture during installation and throughout the life of your project. It also demonstrates impressive electrical insulation properties.
A wide range of additives can be mixed into the resin to create flexible and rigid plastics with specific characteristics like processing aids, anti aging agents, stabilizers, fillers and pigments and flame retardants. Rigid PVC has a high density for a plastic and can be injection molded or solvent cemented to make it strong, hard and long-lasting.
The addition of plasticizers helps reduce the rigidity of the polymer, which makes it more pliable and versatile. This allows PVC to be shaped, cut and formed into the shape required for a specific application. PVC is recyclable and can be formed into a variety of products that include window profiles, pipe and waste pipes, and coated fabrics, such as tarps.
PVC supports diverse field seaming capabilities including chemical adhesives and hot air wedge welding. Wedge welders are state of the art and provide more consistent, reproducible, and higher quality seams than chemical adhesives. These seams are stronger, more durable and longer lasting than traditional stitched seams. In addition, the ability to use the same equipment for both seaming and pond excavation significantly increases efficiency and productivity on your project.
Polyethylene (PE)
Polyethylene (PE) is one of the most popular geomembrane liner materials because it is affordable, chemically resistant and durable. It is also able to withstand environmental factors such as temperature, oxygen partial pressure and the chemical composition of surrounding media that can affect its oxidation rate.
There are two main types of PE: High-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE). Both are produced through the ethylene production process, catalyst polymerization, chain growth control, cooling and solidification. The resulting product is then converted into pellets for further processing.
PE is used in products such as cutting boards, juice containers, plastic lumber, toys, picnic ware, cable insulation and garbage bags. It is a translucent/waxy plastic with excellent weatherproofing properties and remains Green 3D Geomat tough at very cold temperatures. It is also easy to recycle and offers good chemical resistance.
LDPE is commonly found in the bottoms of landfills as well as in the lining of wastewater treatment plants and water storage tanks. It is also used in commercial nurseries and by farmers for pond liners and soil waterproofing.
Both LDPE and HDPE are highly resistant to UV radiation. They are also able to withstand exposure to harsh chemicals, including petroleum-based fluids. At fracking locations, LDPE and HDPE are used as pad liners, secondary containment and floating covers. Floating covers consist of two insulated sheets of foam surrounded by a geomembrane.