The thermal oxidation of hydrogenated acrylonitrile-co-butadiene rubber from ambient to 150 °C

摘要

Hydrogenated acrylonitrile-co-butadiene (HNBR) elastomers containing three concentrations of acryloni-trile (34, 39 and 50 wt%) and less than 1% residual double bond content were heat aged up to 150 °C. Fourier transform Infrared (FTIR) spectroscopy, elemental analysis and liquid proton Nuclear Magnetic Resonance (NMR) were used to analyze the thermo-oxidized samples. FTIR clearly shows the development of esters, ketones, carboxylic acids and secondary alcohols upon heat aging which were confirmed by NMR. The acrylonitrile content was not affected by the employed heat aging conditions. Using the carbonyl growth index and time-temperature superposition (T-TS), the long term thermo-oxidative kinetics possessed three distinct regions: 23-85 °C, 85-100 °C and 100-150 °C. The slower oxidation kinetics between 85 and 100 °C in combination with an induction period shown by T-TS likely contributes to the enhanced oxidative heat aging resistance of HNBR. Activation energies increased with temperature and lower acrylonitrile levels. A series of reaction mechanisms has been put forth to explain functional group development or loss during oxidative heat aging.