OXIDATION RESISTANCE (OIT) – Long Term Reliability of Polymer

Providing long-term protection that is required by geocell polymers is a complicated process requiring a high degree of technical competency – both in the selection of additives and their blending in the manufacturing process. Heat stabilizers enable Neoloy based PRS-Neoweb™ geocells to survive environmental conditions, such as heat and exposure to free radicals (ozone, ionizing radiation, oxidative processes in soil, sewage and industrial waste) for many years.

Heat stabilizer content is measured by the Oxidative Induction Time (OIT) method. OIT is an accurate indicator of the long-term reliability of the polymer protection to withstand prolonged exposure to oxidation.  This method is widely used for testing geosynthetics in critical applications.

OXIDATION RESISTANCE      
DESCRIPTION VALUE UNITS TEST METHOD
Oxidative Induction Time (OIT)  > ­ 125 minutes ISO 11357-6, ASTM D3895 
(virgin material prior to any aging) (OIT @ 200°C)
Effective design life to 60 years

his method is performed on a sample strip heated to 200°C in DSC (Differential Scanning Calorimetry) under a protective atmosphere (nitrogen, argon) until melting. Then oxygen is pumped in at high pressure. Under these conditions all the heat stabilizers react and the time until an Exothermic reaction (oxidation) starts is measured. The more UV stabilizer there is in the product, the longer the reaction time will be.

PHOTOCHEMICAL (UV) RESISTANCE (HPOIT)

Stabilizers that prevent polymer degradation from UV radiation belong to the Hindered Amine Light Stabilizers (HALS) family of heat stabilizers; these are essential additives that allow Neoloy based PRS-Neoweb geocells to survive environmental conditions that include heat and direct and diffused solar radiation for many years. The heat stabilizer content is measured by the High Pressure – Oxidative Induction Time (HPOIT) method (ASTM D5885).

PHOTOCHEMICAL RESISTANCE      
DESCRIPTION VALUE UNITS TEST METHOD
Durability to UV Degradation  > ­ 1250 minutes ASTM D5885 
(UV Resistance) (HPOIT @ 200°C)
Effective design life to 60 years

This method is performed the same as OIT on a sample strip heated to 200°C in DSC (Differential Scanning Calorimetry). The more UV stabilizer in the product, the longer the reaction time will be. If HPOIT is greater than 500, and Carbon black is 3% and more of type P, the protection is >50 years.