Loading...
Loading...
LLDPE geomembrane is specified against GRI-GM17, the Geosynthetic Institute standard that sets minimum property values by thickness for smooth and textured linear low density polyethylene sheet. LLDPE trades some of HDPE's chemical resistance for flexibility and strain capacity, which is why it shows up wherever a liner must conform to settlement or deform without failing.
| Property | Test method | GM17 requirement (60 mil smooth) |
|---|---|---|
| Thickness (minimum average) | ASTM D5199 | 60 mil nominal (1.5 mm), lowest individual reading not less than 10 percent below nominal |
| Density | ASTM D1505 / D792 | 0.939 g/cc or lower |
| Tensile break strength | ASTM D6693 Type IV | 228 lb/in width |
| Tensile break elongation | ASTM D6693 Type IV | 800 percent |
| 2 percent modulus (maximum) | ASTM D5323 | 2,400 lb/in width, a ceiling that screens out stiff resin |
| Tear resistance | ASTM D1004 | 33 lb |
| Puncture resistance | ASTM D4833 | 66 lb |
| Axi-symmetric break resistance strain | ASTM D5617 | 30 percent minimum |
| Carbon black content | ASTM D4218 | 2.0 to 3.0 percent |
| Carbon black dispersion | ASTM D5596 | Category 1 or 2 for at least 9 of 10 views |
| Standard OIT (oxidative induction time) | ASTM D3895 | 100 minutes or higher |
| Nominal thickness | Tensile break strength (ASTM D6693) | Tear resistance (ASTM D1004) | Puncture resistance (ASTM D4833) |
|---|---|---|---|
| 40 mil (1.0 mm) | 152 lb/in width | 22 lb | 44 lb |
| 60 mil (1.5 mm) | 228 lb/in width | 33 lb | 66 lb |
| 80 mil (2.0 mm) | 304 lb/in width | 44 lb | 88 lb |
| 100 mil (2.5 mm) | 380 lb/in width | 55 lb | 110 lb |
GRI-GM17 is the Geosynthetic Institute's standard specification for smooth and textured linear low density polyethylene geomembrane, the direct counterpart to GRI-GM13 for HDPE. Like GM13, it publishes minimum property values by thickness with the ASTM test method and testing frequency attached to each property, so a specifier can cite one document instead of writing resin and sheet requirements from scratch.
The differences between the two standards describe the differences between the two materials. GM17 caps density at 0.939 g/cc where GM13 sets a floor at 0.940 g/cc, because lower crystallinity is what makes LLDPE flexible. GM17 requires 800 percent break elongation against GM13's 700 percent, adds a 2 percent modulus ceiling so a stiff sheet cannot be sold as LLDPE, and requires a 30 percent minimum axi-symmetric break strain per ASTM D5617, a multiaxial test GM13 does not include. In exchange, GM17 drops the notched constant tensile load stress crack requirement, because stress cracking is a high-crystallinity failure mode that LLDPE resists by nature.
LLDPE is selected when the design expects the liner to deform. The ASTM D5617 axi-symmetric test inflates a specimen like a balloon until it breaks, and the 30 percent strain minimum in GM17 is a direct proxy for how well the sheet tolerates out-of-plane deformation: differential settlement under a landfill cap, subsidence over waste, ore load pressing a heap leach liner into subgrade irregularities, or a pond floor built over compressible soils.
That capacity comes with tradeoffs a submittal reviewer should keep in view. LLDPE has somewhat lower chemical resistance than HDPE, particularly against hydrocarbons, and slightly lower tensile strength at the same thickness. Where the containment chemistry is aggressive and the subgrade is stable, HDPE remains the default; where the chemistry is moderate and deformation governs, LLDPE earns its place. Many designs split the difference, placing HDPE on floors that see solution chemistry and LLDPE on caps and closures that see settlement.
LLDPE follows the same thickness logic as HDPE: 40 mil for lighter-duty covers and ponds, 60 mil as the workhorse, and 80 to 100 mil where loads and service life demand more. Landfill final covers and closures are the classic LLDPE application, because a cap rides on waste that will settle for decades and the liner must follow it without tearing.
In our markets, LLDPE also appears on heap leach pads where the design calls for conformance under high ore loads, on ponds and impoundments over compressible or collapsing soils, and in agricultural and wastewater lagoons where the containment chemistry does not demand HDPE. Smooth and textured sheet are both published in GM17, with textured LLDPE specified on slopes for interface friction exactly as with HDPE.
LLDPE welds with the same equipment and procedures as HDPE: dual-track hot wedge fusion for long panel seams and extrusion fillet welding for details, patches, and penetrations. Seam minimums come from GRI-GM19, which publishes shear and peel values for LLDPE by sheet thickness and weld type, slightly lower than the HDPE values at the same thickness in keeping with the softer sheet.
Nondestructive testing covers 100 percent of field seams, with air pressure testing of dual-track fusion seams per ASTM D5820 and vacuum box testing of extrusion welds per ASTM D5641. Destructive samples are cut on the frequency the specification sets and tested in shear and peel per ASTM D6392, with the film tear bond criterion applying just as it does for HDPE: the specimen must fail in the sheet, not through the weld.
A complete LLDPE submittal pairs the manufacturer's product data sheet, stating conformance to GM17 for the specified thickness and surface, with roll-specific quality control certificates reporting thickness per ASTM D5199, density per ASTM D1505 or D792, tensile properties per ASTM D6693, tear per ASTM D1004, puncture per ASTM D4833, axi-symmetric strain per ASTM D5617, carbon black content and dispersion per ASTM D4218 and D5596, and standard OIT per ASTM D3895.
The installation side adds welder qualifications, the proposed panel and seam layout, trial weld procedures, and the field seam testing plan. One LLDPE-specific check is worth making explicit: confirm the density on the certificates actually sits at or below 0.939 g/cc, because a sheet that drifts above it is HDPE by definition and will not deliver the strain capacity the design assumed.
Heap-leach pads, tailings impoundments, solution channels, and evaporation ponds.
Send us your project specification and we will match materials, assemble submittal data, and scope the installation.