Expertise Determination of degradation and stability (durability) of polymeric materials:

There are several reasons to determine the stability of polymeric materials. The most important ones are:

• The determination of the service life.
• Comparison of different materials, grades or stabilizer recipes.
• To determine if the quality of a material is not changing over time (quality control).

In many cases the required service life of a material is many years. Therefore it is unrealistic to determine the lifetime of these materials at their application conditions. Consequently accelerated testing has to be done. Results from these tests have to be extrapolated to the lifetime in the environment at which the polymeric material is applied, which is highly complicated and requires a large expertise.

Comparison of materials is in general less complicated, although the condition chosen to do the comparison should give the same ranking as can be expected in the application environment. This requires insight In the failure mechanism at the application conditions, which is not always available.

The quality control test is least difficult. In such a test potential production mistakes should be determined. The majority of the quality control tests are able to determine if for instance the addition of stabilizers was forgotten.

All these test should be able to tell differences at application conditions and should therefore be related to the mechanism determining the lifetime at application conditions. Consequently for different degradation rate determining mechanism different evaluation tests should be applied.

The scientific knowledge related to different aspects of accelerated ageing and the use and miss use of these tests to forecast the service life of polymeric materials is part of my expertise. This counts for long-term heat stability including shelf-life determinations, UV-stability or outdoor durability, hydrolytic stability, bio-degradation and biostability.