Chemical aging of polymers - Physico-Chemical Stabilization

The first two dossiers dealt with ageing phenomena on a macroscopic scale, their interpretation on a macromolecular scale [AM 3 151] and the mechanisms involved on a molecular scale, with their kinetic modelling enabling lifetimes to be predicted in a non-empirical way [AM 3 152] . As it happens, most widely distributed polymer materials are relatively unstable in the presence of radiation, environmental agents such as oxygen or water, and degrade too quickly to be able to retain their functional properties for a sufficiently long time for the industrial applications they are intended for. Stabilizers are therefore added to slow down degradation processes during processing and subsequent use. It should be noted that the industrial use of these polymers has only become possible with the use of these molecules . When a part is being developed, several formulations of stabilized polymers are generally subjected to accelerated aging in the laboratory, and the best is selected - an empirical approach that is costly in terms of time, human resources and equipment. The purpose of this dossier is to review the mechanisms of action of the main additive families, so that formulators can better understand the results obtained in the laboratory and any discrepancies observed with natural aging. It also shows how the models presented in [AM 3 152] can be supplemented to provide a non-empirical tool for predicting the lifetime of a stabilized polymer through kinetic modeling.