Understanding H₂O₂-Induced Thermo-Oxidative Reclamation of Vulcanized Styrene Butadiene Rubber at Low Temperatures

Abstract

Recombination reactions often occur in the process of chemical, thermal, or mechanical degradation of vulcanized styrene butadiene rubber (SBR), which hinders the recycling efficiency of waste tire rubbers. In this work, we developed an effective method to transform solid vulcanized SBR into reclaimed rubber with 100% sol fraction through a hydrogen peroxide (H 2 O 2 )-induced thermo-oxidative reclamation process at 100 °C with the assistance of soybean oil. The structural evolution of the vulcanized SBR and the role of H 2 O 2 and soybean oil in the reclaiming process were investigated by sol−gel analysis, gel permeation chromatography (GPC), attenuated total reflectance− Fourier transform infrared spectroscopy (ATR−FTIR), and 13 C nuclear magnetic resonance ( 13 C NMR) spectroscopy. The results showed that vulcanized SBR underwent severe oxidative scission, the sol of the reclaimed samples increased from 20.4 wt % up to 100 wt % with a decreased molecular weight to 1.378 × 10 4 g/mol. Multiple functional groups such as carboxyl, hydroxyl, and ether groups were generated in the polymer chains as confirmed by 13 C NMR and FTIR spectroscopy. Moreover, the reaction pathway of the oxidative reclamation was quantified by density functional theory (DFT) calculations, suggesting that hydroxyl radicals were generated from a homolytic cleavage reaction of H 2 O 2 with SBR by hydrogen abstraction and accelerated the rate-determining step of the SBR oxidation. The apparent activation energy (E a ) of the initial stage of the oxidative reclamation decreased from 223 to 160 kJ/mol according to the model-free kinetics results.

Efficient thermo-oxidative reclamation of green tire rubber and silanized-silica/rubber interface characterization

“…And the mechanism of oxidative reclamation has already been reported by our previous reaserch. 13 The r-SS210 and r-SS230 contained relatively low ratio of residual rubber which indicates the high reclamation degree of the waste green tire rubber and high silica proportion in r-SS. to silica, the exist of bound rubber formed a week peak at 40° and which is weakened with the increase of reclamation degree.…”

“…Moving forward, a more efficient, energy-saving and environmental-friendly method is needed for recycling of fillers from waste green tire rubber . According to our previous studies on the thermo-oxidative reclamation of waste tire rubbers 12,13 , with the assistance of a small amount of vegetable oil, a high reclamation process of waste tire rubber under low temperature (150 o C) was achieved within xx (how long?). The vegetable oil can effectively swell the rubber matrices thus facilitates the penetration of oxygen and thermo-oxidative degradation.…”

4R of rubber waste management: current and outlook

“…The mixed sample was then heated in a drying oven at 100 °C for 4 h with consistent air supply. After 4 h, the experiment yielded 100% sol fraction, suggesting complete devulcanization of the rubber [ 89 ]. Another study by Sabzekar et al in 2015 investigated the effect of reaction time, temperature, and the amount of benzoyl peroxide as devulcanizing agent on the devulcanization efficiency of sulfur-cured NR.…”

Reinforcing and plasticizing effects of reclaimed rubber on the vulcanization and properties of natural rubber

“…Biodegradable and low toxicity soybean oil is a natural softener, 33 and has the ability to penetrate and swell the cross‐linked network of GTR, which is helpful to promote the degradation of GTR. Zhang et al 34 made vulcanized SBR completely degraded at a lower temperature (100°C) by a hydrogen peroxide‐induced thermo‐oxidative reclamation process with the assistance of soybean oil. Song et al 35 also prepared the RR with a higher reclamation degree by thermo‐oxidative reclamation method with the synergistic effect of the soybean oil and the obtained RR might be used as a reinforcing filler for tires.…”