Combined in situ infrared and mass spectrometric analysis of high-energy heavy ion induced degradation of polyvinyl polymers

Degradation of polyvinyl polymers (polyvinyl formal, polyvinyl alcohol, and polyvinyl acetate) by high-energy heavy ions was analysed with in situ mass spectrometry and infrared spectroscopy. Both at room temperature and at cryogenic temperature, the polymers are severely damaged by scission of side chains and the polymer backbone, releasing a large number of molecular fragments. Correlation of structural analysis of the damaged polymer and mass analysis of its volatile fragments gives plausible reaction mechanisms for the ion induced degradation. These are compared to thermal degradation. The differences found between the two degradation processes are due to the non-equilibrium character of the ion based process with its high electronic excitation and ionisation. The results are of practical relevance for applications of the polymers in devices of particle accelerators and space vehicles.