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Common Antioxidant in Most Geosynthetics Found to Decompose by Multiple Pathways



By GNA Editor | 13th December 2023


Geosynthetics play a crucial role in modern civil engineering and environmental protection, offering various applications from geomembranes to geogrids. High-density polyethylene (HDPE) and polypropylene (PP) are two commonly used polymers in geosynthetics, and the stability of these materials over long service lifetimes is paramount. This paper focuses on the widely utilized antioxidant, Irganox 1010, its degradation mechanisms, and the implications for geosynthetic service life. We explore the need for alternative antioxidants, such as Irganox 1330, and the cost implications associated with their adoption.

The breakdown of Irganox 1010 reduces its antioxidant effectiveness and leads to conversion products that are smaller and less bulky and thus more easily lost from the polymer by extraction, leaching and blooming. All these side reactions and degradation reactions of Irganox 1010 service to reduce its effectiveness and lead to reduced service lives of the geosynthetic products and in some case premature failure.

1. Introduction:

Geosynthetics are extensively employed in civil engineering and environmental applications due to their unique properties. Geomembranes, geogrids, and geonets, among others, are essential components of various infrastructure projects. High-density polyethylene (HDPE) and polypropylene (PP) are predominant polymers used in geosynthetics, and their longevity is a critical factor in ensuring the effectiveness of these materials over the long term.

These formulations are designed to enhance the flexibility, adhesion, durability, mechanical properties, and water tightness of the cementitious coating on the geosynthetic substrate.

2. Irganox 1010: An Antioxidant for Geosynthetics

Irganox 1010, a member of the hindered phenol family of antioxidants, has been a popular choice in stabilizing HDPE and PP against oxidative degradation. It functions by trapping free radicals, effectively inhibiting free-radical oxidation reactions that can lead to embrittlement of these polymers.

3. Degradation Mechanisms of Irganox 1010:

Despite its widespread use, Irganox 1010 has been found to undergo degradation through multiple pathways during service. These degradation reactions can significantly affect the stability and service life of geosynthetics.

3.1 Hydrolysis:

Hydrolysis is a common degradation pathway for Irganox 1010, particularly in the presence of moisture and high temperatures. This process leads to the cleavage of ester linkages in the Irganox 1010 molecule, rendering it less effective in suppressing oxidation.

3.2 Oxidation Reactions:

Irganox 1010 can also undergo oxidation reactions, further compromising its antioxidant properties. Oxidation reactions generate oxidative products that are less efficient in preventing polymer degradation.

3.3 Addition and Scission Reactions:

Additional degradation mechanisms include addition and scission reactions, which result in the fragmentation of the Irganox 1010 molecule. These reactions not only reduce its antioxidant effectiveness but also lead to the formation of smaller, more extractable fragments.

See other reaction pathways of Irganox 1010 below:

4. Implications for Geosynthetic Service Life:

The degradation of Irganox 1010 within geosynthetics has profound implications for their service life. Reduced antioxidant effectiveness can lead to premature failure of these materials, potentially compromising the integrity of civil engineering projects and environmental protection efforts.

5. Alternative Antioxidant: Irganox 1330:

Recognizing the limitations of Irganox 1010, Scheirs and others have proposed the adoption of alternative antioxidants. Irganox 1330, in particular, offers improved hydrolytic stability compared to Irganox 1010.

6. Cost Considerations:

While Irganox 1330 presents a more stable alternative, it is also more expensive. Therefore, the transition from Irganox 1010 to Irganox 1330 must be evaluated in terms of cost-effectiveness for geosynthetic products.

7.  Conclusions:

The stability and longevity of geosynthetics are of utmost importance in civil engineering and environmental applications. Irganox 1010, a commonly used antioxidant, undergoes degradation through various pathways, diminishing its effectiveness. The adoption of alternative antioxidants, such as Irganox 1330, offers enhanced stability but comes at a higher cost. A careful evaluation of the trade-offs between stability and cost is essential when considering the transition to alternative antioxidants in geosynthetic materials. Further research is needed to develop cost-effective solutions that ensure the long-term performance of geosynthetic products in the field.

See host of Irganox 1010 conversion products in table below:

  1. Scheirs, J., et al. (1996). “Conversion Products Formed during Degradation of Phenolic Antioxidants.” https://pubs.acs.org/doi/10.1021/ba-1996-0249.ch024
  2. Scheirs, J. (2009). “Evaluation of Antioxidants for Polyethylene and Polypropylene in Geomembranes” https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=9853&context=etd

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