Conflict with BIS Indian Standard IS16352 for Geosynthetics

Q: We are a manufacturer of HDPE and have run into a conflict with the BIS Indian Standard IS16352 for Geosynthetics — High Density Polyethylene (HDPE) Geomembranes for Lining — that requires a geomembrane made with HDPE resin density greater than 0.94 g/cm3. Can you help?

A: Most HDPE geomembranes are manufactured from polyethylene resin granules with a density below 0.94 g/cm3. These resin granules are blended with a carbon black masterbatch to form a “let-down” which is entered into the hopper of the extruder. The masterbatch contains 2% and 3% carbon black with a density of about 1.3 g/cm3. Hence, the final “formulated” density of the geomembrane is greater than 0.94 g/cm3, not the raw density of the polyethylene resin granules. This is standard practice in the geomembrane industry. It enables HDPE geomembranes to achieve durability requirements, stress-crack resistance and long lifetimes.

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