The recycling of waste rubber is very important for environmental protection, but the compatibility problem restricts the recycling and application of waste rubber powder (WRP). Devulcanization of WRP has been proven to be an effective method to improve the solubilization effect. The use of environmentally friendly nontoxic solvents can not only improve the devulcanization effect but also avoid secondary pollution. Thus, in this article, an environmentally friendly deep eutectic solvent (DES) is first prepared and then applied to the devulcanization treatment of WRP. The results show that the prepared DES has a positive devulcanization effect, and the devulcanization rate can reach 50%. The devulcanization mechanism can be divided into two aspects: (1) adsorption and removal of sulfur-containing low-molecular compounds and (2) destruction of the crosslinking structure and improvement of fluidity. Observation of the microstructure showed that the rougher the surface of the desulfurized rubber powder, the more conducive to the crosslinking reaction with the matrix material to form a uniform whole. The devulcanization mechanism of DES is divided into destroying the sulfur-containing cross-linked structure and adsorbing the sulfur-containing low-molecular compounds. The surface of WRP after DES treatment is rougher and more porous, which is beneficial to the crosslinking reaction with the matrix material. Finally, the optimum process conditions for the de-crosslinking effect are determined by orthogonal test as follows: liquid-solid ratio 15∶1, temperature 120°C, time 0.5 h.
Massive production and consumption of ground tire rubber (GTR) for transportation have led to significant waste rubber accumulation, posing a serious environmental threat. Rubber devulcanization technologies, as a promising strategy for rubber recycling, still face several challenges, including high consumption, pollution concerns. This study proposes an innovative method for rubber devulcanization using dielectric barrier discharge (DBD) plasma. Experimental results demonstrate a significant reduction in crosslink density, decreasing from 2.1 × 10 −4 mol/cm 3 to 0.8 × 10 −4 mol/cm 3 , after plasma treatment at a discharge voltage of 18 kV for 30 min. This reduction is accompanied by a decrease in gel content from 96.79 to 90.54%, indicating the effective cleavage of S-S and C-S bonds within GTR. Notably, after plasma treatment, the tensile strength and elongation at break of the regenerated rubber reached 10.2 MPa and 357.7%, respectively, meeting the standards for high-grade rubber. These mechanical properties meet the standards for high-grade rubber, rendering the devulcanized rubber suitable for reuse in industrial manufacturing processes. However, when the discharge voltage surpasses a critical level, the electron energy attains a magnitude sufficient to cause extensive structural damage to the rubber backbone of GTR. Consequently, this degradation results in a significant reduction in the molecular weight of the regenerated GTR, which ultimately leads to a decrease in both tensile strength and elongation at break. Based on a comprehensive analysis of experimental data and characterization results, a plausible mechanism for plasma-assisted devulcanization is proposed, highlighting the significant potential to enhance environmental sustainability and support circular economy initiatives.
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