Analysis of polyolefin stabilizers and their degradation products

Polymeric materials are complex samples, as they contain various groups of additives, compounding ingredients, and fillers. An important group of additives are stabilizers. Efficient stabilization is essential especially for polypropylene, as it is sensitive to oxidation and radical attack due to the numerous tertiary carbon atoms in its structure. How long a polymer will be sufficiently stabilized can be deduced from the contained amount of intact stabilizer. Different approaches for the analysis of stabilizers in polyolefins are available, which include sample preparation with subsequent chromatographic separation as well as direct analysis techniques. In round-robin tests, stabilizer concentrations obtained varied strongly. This shows the demand for reliable and robust methods. Stabilizers get consumed while protecting the polymer and are then present as degradation products. They were observed while quantifying intact stabilizers, in migration studies, and - if volatile - in emission studies of polymers. Furthermore, e.g. interactions with other polymer ingredients or irradiation degraded stabilizers. The identification of degradation products provides a better insight into the reactions associated with stabilization. Their quantitation makes it possible to deduce the original level of stabilization. Furthermore, polymer ingredients degrading stabilizers can be identified. Knowledge on these interactions contributes significantly to improved polymer stabilization.