Study on Preparation of Rubber Reinforcement Filler by Air-flow Classification and Modification of Coal Gangue

Purposes As a coal based solid waste rich in silicon and aluminum oxides, utilization of coal gangue is crucial for the sustainable development of coal industry. Methods Integrated grinding modification of calcined coal gangue and aluminate coupling agent to prepare rubber reinforcement was proposed. The influences of grinding time and the amount of modifier on the surface modification were investigated. Ultrafine particles were obtained through air flow classification, and the influences of modification or not and particle size on the reinforcing and filling properties of rubber were analyzed. Findings The results show that the best comprehensive modification effect is achieved when the duration of ball milling is 30 min and the amount of aluminate coupling agent is 2%. The characteristic functional groups of aluminate coupling agent appear on the surface of coal gangue. Compared with the rubber filled with commercial silica, the rubber filled with the air-flow graded modified filler possesses higher hardness and crosslinking density, its vulcanization performance is better, the tensile strength, elongation at break and permanent deformation at break are reduced, and the fixed extension stress is increased. The particle size distribution of the filler has an obvious effect on the properties of rubber, with the decreases of the particle size of the filler, the vulcanization property is improved, and the tensile property is also improved. The reinforcement performance of modified superfine coal gangue as filler is close to that of silica, which has the potential to replace silica.