Study of rubber compounds with recycled rubber obtained by different methods

The most common way to eliminate rubber wastes is to deposit them in a landfill: these stocks represent a serious problem for the environment (fire danger) and for people’s health (rodents, mosquitoes and other plagues). Different methods have been developed in order to overcome this situation: however, because of the inherent structure network of rubber compounds, the strength of sulfur/rubber bonds (vulcanization process) and the different formulation, the recycling is currently a challenge. Several grinding, ultrasonic, biological, chemical, thermomechanical and thermochemical devulcanization processes have been studied: the latter ones are the most used in industry. These two methods are different: in the thermomechanical process, the material is submitted to high shear strain, at a controlled pressure and temperature, stretching the network of the rubber and some additives, such as oils or reclaiming agents, can help the devulcanization stage. The thermochemical process involves the use of chemical agents that break C-C or S-S bonds. Devulcanizing chemical agents could be disulfides, hydroxides, chlorinated hydrocarbons or thiol-amine reagents. Starting from this consideration, two compounds realized with rubber waste previously treated with thermomechanical and thermochemical devulcanization processes have been characterized and their properties have been evaluated in a chemical, physical-mechanical and applicative view.