Effect of Deep Eutectic Solvent Pretreatment on Devulcanization of Waste Rubber Powder

Abstract

The recycling of waste rubber is very important for environmental protection, but the compatibility problem restricts the recycling and application of waste rubber powder. Devulcanization of waste rubber powder (WRP) has been proven to be an effective method to improve the solubilization effect. The use of environmentally friendly non-toxic solvents can not only improve the devulcanization effect, but also avoid secondary pollution. Thus, in this paper, 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. Firstly, adsorption and removal of sulfur- containing low molecular compounds. Secondly, destruction of the crosslinking structure and improvement of the fluidity. The microstructure observation showed that the rougher the surface of the desulfurized rubber powder was, 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 cross-linking reaction with the matrix material. Finally, the optimum process conditions for the decrosslinking effect are determined by orthogonal test as follows: liquid-solid ratio 15∶1, temperature 120°C, time 0.5 h.