This project funded a PDRA to examin the effects of sour gas ageing on crosslinked HNBR polymer. It focused on the changes to the network structure and their relationship with physical properties. The study material was an HNBR crosslinked with a typical sulphur-based cure package (no fillers or other additives were used - in order to simplify data interpretation). Sourcing, compounding and moulding of the rubber parts will be undertaken by ARTIS. This project exploited and validated the new ARTIS sour gas ageing facilities. The bahviour of the aged materials was contrasted to the unaged material at QMUL.