Are Your HDPE Geomembranes Really Built for the Long Haul?

In challenging environments, from landfills to industrial waste containment, long-term durability is non-negotiable. Yet, many industry standards may be leaving critical gaps in protection. In our latest article, we dive into the importance of both Oxidative Induction Time (OIT) and High-Pressure Oxidative Induction Time (HPOIT) testing and why these are essential for ensuring HDPE geomembranes perform in the harshest conditions. Discover how Atarfil’s HD EVO goes beyond the standard to offer unmatched longevity and resistance.

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

What is OIT?

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

• Phenols: These primary antioxidants stabilize free radicals during the service life of the geomembrane, preventing polymer degradation from thermal exposure.

• Phosphites: Secondary antioxidants, which act mainly during the manufacturing process, protect the polymer from degradation during high-heat processing.

The goal of OIT is to simulate long-term material performance by accelerating oxidation in a controlled environment. This allows for a quicker, more affordable assessment of how well the geomembrane will resist degradation under thermal stress.

What is HPOIT?

High-Pressure Oxidative Induction Time (HPOIT) is a complementary test that also measures oxidative stability but at a lower temperature (150°C) and a much higher pressure (3500kPa). The increased pressure speeds up the oxidation process, allowing for quicker assessment of antioxidant performance.

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

HPOIT is essential for applications where geomembranes are exposed to UV radiation and aggressive chemicals. Like OIT, HPOIT is an accelerated test, simulating long-term UV and chemical exposure in a lab environment to quickly compare the durability of different materials.

Why Both OIT and HPOIT Are Necessary

While some standards like GRI GM13 require either OIT or HPOIT, Atarfil emphasizes the importance of both tests. This approach ensures that the geomembrane can withstand the dual stresses of thermal oxidation and UV exposure.

Key Reasons Why Both Tests Are Critical:

1. Thermal Oxidation Protection: OIT measures the performance of phenols and phosphites, which protect the material from heat-induced oxidation. This test is crucial for high-temperature environments where heat could degrade the liner over time.

1. UV Protection: HPOIT assesses HALS, which provide long-term protection from UV-induced oxidation. HALS regenerate during exposure to sunlight, extending the geomembrane’s lifespan in outdoor applications.

1. Accelerated Testing for Practical Use: Both OIT and HPOIT are accelerated tests designed to speed up the degradation process in a lab environment, making it possible to quickly compare different materials without the time and expense of real-world testing over decades.

By specifying both OIT and HPOIT, Atarfil ensures that their geomembranes offer superior durability in environments exposed to thermal stress and UV radiation, providing comprehensive protection across a range of applications.

Comparison: Atarfil’s HD EVO vs. GRI GM13

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 Crack Resistance (SCR):

GRI GM13 HDPE (Industry Benchmark) Comparison to Atarfil EVO HDPE

OIT and HPOIT Comparison:

• GRI GM13 sets the minimum requirement for OIT at 100 minutes and HPOIT at 400 minutes. While these values provide basic protection against thermal oxidation and UV radiation, Atarfil’s HD EVO geomembranes consistently exceed these minimums, offering superior durability.

• Atarfil’s approach includes both OIT and HPOIT testing, which ensures that the geomembrane will perform under both thermal and UV stresses. This dual protection is essential for applications exposed to direct sunlight, chemicals, or high temperatures.

Stress Crack Resistance (SCR) Comparison:

• GRI GM13 mandates a minimum SCR of 500 hours, which is sufficient for many general applications. However, Atarfil’s HD EVO geomembranes boast SCR values greater than 3,000 hours, offering vastly superior resistance to cracking caused by environmental stressors like temperature fluctuations and mechanical stress.

This extended SCR performance significantly reduces the risk of premature failure, making Atarfil geomembranes more reliable for long-term containment solutions, particularly in demanding applications such as landfills, mining, and industrial waste storage.

The Role of Antioxidants in Long-Term Durability

Antioxidants are critical in ensuring 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 due to heat. Phenols stabilize free radicals over the geomembrane’s service life, while phosphites protect the material during high-heat manufacturing processes.

• HALS (Hindered Amine Light Stabilizers): HALS provide superior protection from UV degradation, preventing polymer breakdown from sunlight exposure. They are designed to regenerate during oxidation, offering continuous protection over long periods of UV exposure.

By using high-quality resins and advanced antioxidant formulations, Atarfil’s HD EVO geomembranes are built to withstand thermal oxidation, UV radiation, and chemical exposure, ensuring long-term reliability in even the most demanding environments.

Conclusion

When specifying HDPE geomembranes for challenging applications, it’s crucial to consider both OIT and HPOIT tests to ensure long-term durability. While standards like GRI GM13 provide a baseline for durability, Atarfil goes beyond by requiring both tests, guaranteeing superior performance. OIT measures the geomembrane’s ability to resist thermal oxidation, while HPOIT provides insights into its UV stability—together, these tests offer a complete picture of the material’s long-term performance.

With significantly higher SCR values and extended OIT/HPOIT performance, Atarfil’s HD EVO geomembranes offer unmatched protection against environmental stressors. Whether for landfills, mining applications, or industrial waste containment, Atarfil ensures that its geomembranes will stand the test of time, providing the reliability and durability you need for critical containment systems.