Aging during Service

Two different approaches for lifetime prediction are presented. The underlying lifetime limiting processes have been identified in two cases. Mathematical expressions of chemical/physical relevance were used for the lifetime predictions for PE hot-water pipes and cables insulated with plasticized PVC. Accelerated testing, extrapolation and validation of the extrapolation by assessment of the remaining lifetime of objects aged during service conditions for 25 years were successfully applied to cables insulated with chlorosulfonated polyethylene. Polyolefin pipes exposed to chlorinated water showed a very complex deterioration scenario and it was only possible to find a method suitable for predicting the time for the depletion of the stabilizer system. 

The exposure of synthetic mbber nanocomposites during service against environmental influences like oxygen, temperature, static and dynamic mechanical load or UV-light effects aging processes. 

Ageing of polymers leads to drastic changes to their physical and mechanical properties. Hindered phenols are the most important antioxidants for polyolefins. However, some of the transformation products from these antioxidants can lead to discoloration during service life. In PP, mixtures of phosphites, hindered phenols and lactones are widely used [10-13]. Hindered phenols are very effective... 

Protect the substrate surface so that weak boundary layers do not develop during processing of the joint or during aging in service. 

They can be exposed to various and complex environments during service life, such as harsh and changing weather conditions or contact with alkaline media, with possible additional sustained mechanical loads. Such environments play a key role in the mechanisms and kinetics of ageing and consequently in changes in material properties. 

During processing, only chemical, no physical aging processes occur. Processing, however, determines the physical structure of the finished part and thus influences physical aging and diffusion-controlled degradation during service. Fig. 4.1. 

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