Effect of crosslinking density on the diffusion of antioxidant in XLPE matrices

A Fourier Transform Infrared spectrometer equipped with a microbeam accessary and a linear translation stage with a pinhole mask was used to monitor the diffusion of antioxidant in crosslinked polyethylene (XLPE) matrices crosslinked with controlled amounts of crosslinking agent. Integration of the peak area for a characteristic peak of the antioxidant at different positions along the sample indicated the changing concentration due to diffusion within 30 days. This technique allowed us to study an antioxidant with a molecular weight in the thousand range. The diffusion coefficients calculated were in the order of 10 −11 – 10 −10 cm 2 ·s −1 . It was observed that the diffusion constants dramatically changed with the crosslinking density.