Effect of physical ageing of polymers on dielectric permittivity and loss values over wide temperature and frequency ranges

Ageing of polymeric materials such as PS, PVC, PET occurs strongly in the region of the low temperature tail of the αa relaxation process. This ageing process increases the dynamic modulus, decreases dynamic mechanical and dielectric tan δ, but has little effect on the dielectric constant. The major effect of ageing is the reduction in mobility with depression of the relaxation spectrum related to the ageing time and temperature