Evaluation of cross-linking after accelerated photo-ageing of silicone rubber

Silicone formulations based on polydimethylsiloxane (PDMS) were investigated by using a number of analytical techniques. Horizontal attenuated total reflectance Fourier-transform infrared (HATR-FTIR) spectroscopy studies have confirmed the stability of these materials towards photo-oxidation. No significant oxygenated products were detected after 5000h of accelerated photo-ageing. However, by using thermoporosimetry, hardness measurements and densitometry, an important vulnerability of these formulations towards the cross-linking reactions provoked by UV visible radiation was identified. Thermoporosimetry, using the solid-solid cyclohexane transition as a textural probe, was also used to visualize the profile of cross-linking inside the materials by calculation of the mesh size distribution in successive slices of 40 mum in thickness. (C) 2003 Society of Chemical Industry.