Aspects of the Ageing of Elastomeric Materials

Abstract

Rising raw materials prices and increasing customer demands for reliability and durability mean that there is huge interest in finding more and more ways of improving the service life of elastomeric products, for economic and environmental reasons, by boosting their resistance under the relevant operating conditions. The material-dependent oxygen absorption capacity and oxygen permeability play an important role in oxidative ageing processes and their modelling. Thus, ageing resistance is substantially dependent on the rate of oxygen diffusion into the bulk of the material in the case of thermo-oxidative attack. To evaluate the resistance of materials to external influences, artificial ageing methods are used in practice. The advantage of these methods is that, as a result of intensifying the test parameters, e.g. temperature and humidity, the ageing processes in the vulcanisate are accelerated. Within the scope of this study, the influence of accelerated ageing on the mechanical and viscoelastic properties of mainly carbon-black-filled natural rubber (NR) vulcanisates was studied in an oxygen atmosphere at elevated temperature and in oxygen with solar radiation. The filler content was varied and the antioxidant IPPD was used. The analyses showed that, as well as mechanical properties such as hardness and tensile strength, the viscoelastic properties are also affected, depending on the ageing time and the type of ageing. In addition to the investigation of mechanical properties, a direct evaluation of the material change was carried out for selected samples by means of analytical tests. The investigations showed the deterioration of the antioxidant activity.