1. What is LLDPE Geomembrane
These make installers prefer LLDPE Geomembrane because this material is easy to install, especially in winter. Selecting the correct type of geomembrane liner depends on several variables, such as the design of the anti-seepage application, the type of base and cover layers, chemical, physical and biological stresses, application environment, cost and service life.
LLDPE geomembranes have been extensively utilized in diverse engineering applications, including water conservancy projects, environmental protection initiatives, and landfill construction, due to their remarkable flexibility, durability, and cost – effectiveness. However, beneath their surface of advantages lies a set of limitations that are often overlooked or underestimated. Exploring the disadvantages of LLDPE geomembranes is crucial for a comprehensive understanding of their performance, enabling engineers, designers, and decision – makers to make more informed choices and implement appropriate countermeasures to mitigate potential risks.
1.1Definition of LLDPE Geomembrane
LLDPE Geomembrane is a type of polyethylene geomembrane. The tensile properties of LLDPE Geomembrane include higher impact resistance and puncture resistance, which is very suitable for installation on soil bases prone to uneven settlement. This tensile property allows LLDPE Geomembrane to “lay flat” better, especially at low temperatures, most other geomembranes (including HDPE Geomembrane) tend to become harder and more difficult to handle.
1.2 LLDPE Geomembrane’s Laying and Weldability
It has outstanding laying and weldability.The lack of sensitivity to stress cracking, coupled with its outstanding laying and weldability, makes it a good material for low-temperature applications, but the chemical conditions in the environment need to be considered.
These make installers prefer LLDPE Geomembrane because this material is easy to install, especially in winter. Selecting the correct type of geomembrane liner depends on several variables, such as the design of the anti-seepage application, the type of base and cover layers, chemical, physical and biological stresses, application environment, cost and service life.
2.LLDPE (Linear Low-Density Polyethylene) Geomembrane is a commonly used geotechnical material with multiple basic functions:
2.1 The Impermeability of LLDPE Geomembrane:
It effectively prevents the penetration of water and liquids and is widely used in reservoirs, dams, landfills and other places.
2.2 The Chemical Resistance of LLDPE Geomembrane:
It has good resistance to a variety of chemicals (such as acids, alkalis and oils) and is suitable for chemical plants and wastewater treatment facilities.Due to the characteristics of polyethylene itself, LLDPE Geomembrane has good chemical corrosion resistance and can be in direct contact with toxic leachate in landfills. In addition, landfill gas is mainly discharged or collected through pipelines to prevent gas leakage. It can play a good gas isolation role in landfill closure.
2.3 The Flexibility of LLDPE Geomembrane:
The material has good flexibility, is easy to lay and construct, and can adapt to terrain changes.In terms of material flexibility and puncture resistance, the flexibility and toughness of LLDPE Geomembrane are very important for landfill closure projects. Because the garbage buried in the landfill is often uneven, and over time, the landfill will have different degrees of uneven settlement, which will make the geomembrane used for closure have higher flexibility requirements. According to ASTM d6693, the yield elongation of LLDPE is much better than that of HDPE. This requires a higher yield elongation linear low-density polyethylene (LLDPE) has greater advantages to meet the requirements of landfill closure projects, which are demanding and require the flexibility of LLDPE Geomembrane. The landfill closure project requires the flexibility and puncture resistance of LLDPE Geomembrane.
By adding anti-UV agents, its weather resistance can be improved and its service life can be extended.
2.5 The Tensile Strength and Ductility of LLDPE Geomembrane:
It has high tensile strength and ductility and can withstand foundation movement and pressure.
2.6 The Environmental Protection of LLDPE Geomembrane:
It can be recycled and meets environmental protection requirements.
2.7 The Cost-Effectiveness of LLDPE Geomembrane:
Compared with other anti-seepage materials, It has a lower cost and is economical and practical.These characteristics make LLDPE Geomembrane widely used in water conservancy, environmental protection and construction.
2.8 The Environmental Stress Cracking Resistance of LLDPE Geomembrane:
In terms of environmental stress cracking resistance, It has a lower density in landfills, and it also has better flexibility, so there will be no environmental stress cracking resistance problem. Therefore, in LLDPE In the international standard for geomembranes GRI gm17, the environmental stress cracking resistance index is not even included in the index range.
3. The advantages of low-density polyethylene (LLDPE) geomembrane include:
3.1 Excellent Flexibility:
It has good flexibility and can adapt to items of different shapes.
3.2 High Tear Resistance of LLDPE:
Compared with other types of plastic films, LLDPE geomembrane has stronger tear resistance and can withstand mechanical shock.
3.3 Light Transmittance:
LLDPE geomembrane usually has good transparency and is suitable for packaging applications that require visualization.
3.4 Chemical Stability:
It has good tolerance to a variety of chemicals and is suitable for packaging chemicals.
3.5 Low temperature performance:
It can still maintain good flexibility in low temperature environments and is suitable for cold chain logistics.
3.6 Good heat sealing:
It has superior heat sealing performance and is suitable for automated packaging production lines.
3.7 Cost-effectiveness:
The production cost of LLDPE geomembrane is relatively low and economical and practical.
These advantages make LLDPE geomembrane widely used in food packaging, agricultural films and industrial applications.
4.Disadvantages of low-density polyethylene (LLDPE) film include:
4.1 Low mechanical strength:
Compared with other plastic films, LLDPE film has low tensile strength and tear strength and is easily damaged during use.
4.2 Poor temperature resistance:
LLDPE film is easily deformed at high temperatures and is not as heat-resistant as some other types of plastics.
4.3 Breathability:
Although LLDPE film has good flexibility, its breathability may make it unsuitable in some applications, such as food packaging.
4.4 Aging:
LLDPE film is prone to aging under ultraviolet radiation or oxidative environments, resulting in brittle material and performance degradation.
4.5 Recyclability:
Although LLDPE can be recycled, its recycling process is relatively complicated and is not as popular as some other plastics.
5.Summary
5.1 Types of geomembrane materials
There are many types of geomembrane materials currently in the industry, each with its own characteristics. The geomembranes currently in widespread use include 80% polyethylene geomembranes and 20% PVC (polyvinyl chloride) geomembranes. The main reason why polyethylene geomembranes are widely used is because of their high cost-effectiveness, providing the best relative performance while maintaining good economics.
5.2 Composition of polyethylene geomembrane
Polyethylene geomembranes are mainly composed of HDPE (high-density polyethylene) and LLDPE (linear low-density polyethylene) geomembranes. The resin of HDPE geomembranes is actually MDPE (medium-density polyethylene), but after adding carbon black to resist ultraviolet rays, the final density of the geomembrane reaches the range of HDPE, which is why HDPE geomembranes are named. LLDPE was originally considered to be low-pressure LDPE (low-pressure low-density polyethylene). Compared with LDPE, LLDPE is more heat-resistant, stronger, and more resistant to environmental stresses. This is due to the polymerization of ethylene and other materials such as butane, hexane and octane.
5.3 Anti-seepage and corrosion resistance of polyethylene geomembrane
In terms of isolating liquids and gases, according to the water vapor permeation test of ASTM E96, the permeability coefficients of HDPE and LLDPE are both less than 1.0*10-13g*cm (cm2*s*Pa), and the amount of leachate that can pass through HDPE and LLDPE is almost negligible. Therefore, both HDPE and LLDPE have excellent anti-seepage performance, and the leakage through HDPE or LLDPE is mainly due to the damage of the material itself. At the same time, thanks to the characteristics of polyethylene itself, HDPE and LLDPE have good chemical corrosion resistance and can directly contact with toxic leachate in landfills.
