A new approach to describe the electrical ageing by considering the distributed nature of processes in polymeric materials

This paper proposes to incorporate the distributed nature of processes at play in polymer insulating materials into the description of their electrical ageing process. Indeed, polymers are disordered systems showing a spatially varying morphology. Their amorphous phase is an active system in which the chain segments are continuously undergoing conformational changes characterized by different relaxation processes each with a characteristic relaxation time. Consequently, processes occurring in these materials do not have a characteristic Debye response and the parameters affecting the electrical ageing process are distributed. The already existing theories describing the ageing process of these materials are highlighted. A multivariate statistical approach is proposed to account for the complexity of the ageing process in these materials. This approach takes into consideration the local values of the different parameters of the ageing process and their distributed environments. The physical and mathematical bases of this new approach are discussed and the ageing process is described in terms of different local processes each one with a characteristic relaxation time. Some experimental techniques which allow quantifying the local values of our approach ordering parameters are proposed.