Thermo-oxidative degradation of vulcanized SBR: A comparison between ultraviolet (UV) and microwave as recovery techniques

This study reports a comparison of thermal-oxidative vulcanized SBR degradation caused by Ultraviolet (UV) or Microwave (MW) irradiations. The surface modifications of the rubber samples were explored by instrumental techniques. The cross-linking degree of the rubber was determined via leaching method and the contact angles with water were measured at room temperature. By increasing the exposure time, the UV-treated v-SBR kept 83.24, 62.65, 39.86 and 33.32% of crosslinks, while the MW-treated samples kept 94.78, 88.85, 86.98 and 80.40%. Besides that, the contact angle was decreased drastically after the UV treatment registering 83.70°, 52.45°, 34.75°, 6.0°, while the MW-treated samples had no significant change in the contact angles values. Fourier Transform Infrared (FTIR) findings indicate that part of the polymeric chain was altered through C–C and C-S bond scissions (softening mechanism) calling the attention to a degradation beside the devulcanization phenomenon (regeneration), corroborated by the total carbon and sulfur mass balance. Assuming that the same energy is applied, the UV irradiation present a very strong regeneration effect comparing to MW irradiations. The results are promising, highlighting UV irradiations as a very strong regeneration tool of rubber which is considered a beneficial for the rubber residue problem facilitating its insertion in new composites.