Correlation between mechanical and microstructural properties of vulcanized polyisoprene, polychloroprene, and nitrile-butadiene rubber subjected to accelerated thermal aging

The purpose of this work was to correlate the effects of thermal aging on the macroscopic properties and microstructural changes for three vulcanized rubber types. The materials were subjected to accelerated thermal aging for periods between 0 and 168 h at 100°C. This aging was evaluated by investigating the mechanical properties and by Fourier transform infrared (FTIR) and Raman analysis. The results showed that subjecting the materials to thermal aging for a longer time decreased the elongation at break and tear strength and increased the hardness, while tensile strength exhibited different behavior and followed a different trend. The spectroscopy analyses indicated that there is a decrease in the amount of C=C present in the polymer as the aging time increased, which could be identified by the decrease in peak intensity at 1537 and 1600 cm⁻¹ in the FTIR and Raman spectrum, respectively. These results were attributed mainly to an increase in cross-link density, which caused degradation of the material, essentially by a loss of ductility. A good linear relation (R² approximately 0.95) between changes in the intensity of FTIR peaks for the C=C signal and changes in elongation at break and hardness was found, concluding that these are good indicators of degradation in elastomers.