In demanding environments, from MSW landfills to industrial waste containment, durability is a must. However, many industry norms and standards leave critical gaps in long-term protection. In our latest article, we discuss the importance of Oxidation Induction Time (OIT) and High Pressure Oxidation Induction Time (HPOIT) tests, and why they are essential to ensure HDPE geomembranes perform under extreme conditions. Discover how Atarfil’s HD EVO geomembranes go beyond the standards to deliver unmatched durability and strength.

When specifying HDPE geomembranes for demanding environments, such as those exposed to UV radiation, chemical exposure or extreme temperatures, long-term durability is key. Two essential tests, Oxidation Induction Time (OIT) and High Pressure Oxidation Induction Time (HPOIT), help evaluate a geomembrane’s resistance to oxidative degradation. In addition, antioxidants such as phenols, phosphites and HALS (Hindered Amine Light Stabilizer) are critical in preventing degradation. This article highlights why both OIT and HPOIT, along with appropriate antioxidant formulations, are necessary to ensure the durability of geomembranes and compares the performance of Atarfil’s HD EVO geomembranes to an industry standard such as GRI GM13.

What is the ILO?

Oxidation Induction Time (OIT) (ASTM D3895) is a test that measures how long a material can resist oxidation when exposed to high temperatures, typically 200°C, and a pressure of 35 kPa. OIT primarily evaluates the performance of antioxidants such as phenols and phosphites.

• Phenols: These primary antioxidants stabilize free radicals during the life of the geomembrane, preventing polymer degradation by thermal exposure.
• Phosphites: Secondary antioxidants that act mainly during the manufacturing process, protecting the polymer from degradation during processing at high temperatures.

The objective of the OIT is to simulate the long-term behavior of the material upon accelerated oxidation in the laboratory. This allows for a faster and more accessible evaluation of the geomembrane’s ability to resist degradation under thermal stress.

What is HPOIT?

High Pressure Oxidation Induction Time (HPOIT) is a complementary test that also measures the oxidative stability of the geomembrane, but at a lower temperature (150°C) and much higher pressure (3500 kPa). The increased pressure accelerates the oxidation process, allowing a faster evaluation of the performance of the antioxidants.

• HALS: HPOIT is particularly valuable for evaluating Hindered Amines Light Stabilizers (HALS), which are antioxidants designed for protection against UV radiation. HALS neutralize free radicals generated by UV radiation and regenerate during oxidation, providing long-term stability to geomembranes exposed to solar radiation.

HPOIT is essential for applications where geomembranes are exposed to UV radiation and aggressive chemicals. Like OIT, HPOIT is an accelerated test that simulates prolonged exposure to UV and chemicals in the laboratory, allowing rapid comparison of the durability of different materials.

Why are both OIT and HPOIT necessary?

Although some standards, such as GRI GM13, require only OIT or HPOIT, Atarfil emphasizes the importance of performing both tests. This approach ensures that the geomembrane withstands the combined stresses of thermal oxidation and UV exposure.

Fundamental reasons why both tests are critical:

1. Thermal oxidation protection: The OIT measures the performance of phenols and phosphites, which protect the material from heat-induced oxidation. This test is crucial in high temperature environments where heat could degrade the geomembrane over time.
2. Protection against UV radiation: HPOIT evaluates HALS, which provide long-term protection against UV-induced oxidation. HALS regenerate during sun exposure, extending the life of the geomembrane in exposed applications.
3. Accelerated tests and their practical use: Both OIT and HPOIT are accelerated tests designed to speed up the degradation process in the laboratory, allowing rapid comparison of different materials without the time and cost of testing under real conditions that could take decades.

By specifying both OIT and HPOIT, Atarfil ensures that its geomembranes offer superior durability in environments where the geomembrane is exposed to thermal stress and UV radiation, providing comprehensive protection in a wide range of applications.

Comparison: GRI GM13 HDPE vs. Atarfil EVO HDPE

When comparing Atarfil’s HD EVO geomembranes to the industry standard GRI GM13, several key performance differences stand out, especially in OIT, HPOIT and Stress Cracking Resistance (SCR):

Comparison of ILO and HPOIT:

• GRI GM13: Sets a minimum value of 100 minutes for OIT and 400 minutes for HPOIT. While these values provide basic protection against thermal oxidation and UV radiation, Atarfil HD EVO geomembranes consistently exceed these minimums, offering increased durability.
• Atarfil: Atarfil’s approach includes both OIT and HPOIT testing, which guarantees the correct performance of the geomembrane under thermal stress and UV radiation. This dual protection is essential for applications exposed to solar radiation, chemicals and/or high temperatures.

Comparison of Stress Cracking Resistance (SCR):

• GRI GM13: Requires a minimum SCR value of 500 hours, sufficient for less demanding applications. However, Atarfil’s HDPE geomembranes achieve SCR values in excess of 3,000 hours, offering significantly higher resistance to cracking caused by environmental stresses, such as temperature fluctuations and mechanical stress.

This increased performance over SCR significantly reduces the risk of premature rupture, making Atarfil geomembranes a more reliable option for long-term containment solutions, especially in demanding applications such as landfills, mining and industrial waste storage.

The role of antioxidants in long-term durability

Antioxidants are crucial to ensure the long-term durability of HDPE geomembranes, especially in environments exposed to UV radiation, heat and chemicals. Here’s how each key antioxidant contributes to geomembrane longevity:

• Phenols and Phosphites: These antioxidants prevent thermal oxidation and protect the geomembrane from degradation caused by heat. Phenols stabilize free radicals during the lifetime of the geomembrane, while phosphites protect the material during the manufacturing process where high temperatures are reached.
• HALS (Hindered Amines Light Stabilizers): HALS offer superior protection against UV degradation by preventing polymer degradation when exposed to sunlight. They are designed to regenerate during the oxidation cycle, providing continuous protection over long periods of UV exposure.

Using high quality resins and advanced anti-oxidant formulations, Atarfil’s HD EVO geomembranes are designed to resist thermal oxidation, UV radiation and chemical exposure, ensuring long-term reliability in even the most demanding environments.

Conclusion

When specifying HDPE geomembranes for demanding applications, it is crucial to consider both OIT and HPOIT testing to ensure the long-term durability of the geomembrane. While standards such as GRI GM13 provide a basis for durability, Atarfil goes further by requiring both tests for its EVO geomembranes, ensuring improved performance. The OIT evaluates the geomembrane’s ability to resist thermal oxidation, while the HPOIT provides information on its stability to UV radiation; together, these tests provide a complete picture of the material’s long-term performance.

With significantly higher SCR values and improved performance in OIT and HPOIT tests, Atarfil HD EVO geomembranes offer unmatched protection from environmental stress. Whether in landfills, mining applications or industrial waste containment, Atarfil ensures that its geomembranes will stand the test of time, providing the reliability and durability needed for critical safe containment systems.