The SKZ Plastics Center is one of the few test laboratories able to accelerate the thermo-oxidative ageing of plastics using the high-pressure autoclave test. This method makes it possible to compare plastics equipped with different stabilizer packages quickly and effectively.
Increased oxygen availability
Compared to conventional oven ageing, the high-pressure autoclave test offers up to ten times faster thermo-oxidative ageing due to increased oxygen availability at moderate temperatures. This makes it possible to evaluate material stability within a few weeks or months. The test specimens are immersed in an aqueous medium, which allows leaching and hydrolysis effects to be taken into account. In addition, the influence of the pH value on ageing can be investigated. This ensures a comprehensive analysis.
Indicator for material failure
The oxygen pressure in the high-pressure autoclave is recorded continuously. This data makes it possible to track the oxygen consumption of the material under investigation during oxidation. For example, it has been shown on polyethylene (HDPE) samples that an increased oxygen demand is associated with a decrease in mechanical properties. A change in oxygen consumption can therefore serve as an indicator for the onset of thermo-oxidative failure of the material. The thermo-oxidative lifetime can be estimated by testing five different combinations of temperature and oxygen pressure with subsequent Arrhenius-type evaluation. For a quick formulation comparison, a one-point test can also be carried out, which does not provide a lifetime estimate, but allows a quick assessment of the performance of the formulation and antioxidants.