Pulverization of end-of-life tires by ultra-high pressure water jet process

Abstract

Abstract Crumb rubber (CR), as a final product from end-of-life tires through size reduction process, has proved an appropriate end product for accumulated discard waste tires all around the world. Unlike pre-existing pulverization methods, such as ambient or cryogenic grinding and solid-state shear extrusion, an entire cool pulverization process utilizing ultra-high pressure water jet (UHPWJ) was proposed in this paper. Pulverization experiments under various processing parameters were designed and conducted. The particle size distributions of produced CR were obtained using laser particle analyzer. Microscopic morphologies of CR and rubber fracture surface were observed under scanning electron microscopy. The crosslink density and gel fraction of produced CR were experimentally determined. Influence of four main processing parameters as pump pressure, transverse velocity, standoff distance and impacting angle was discussed in detail, and the most suitable processing parameters were recommended. The results show that the particle size distribution of produced CR with UHPWJ is between 45 μm and 200 μm, and the surface of CR is coarse and porous. High compressive shear effect and erosion are the main mechanisms in UHPWJ pulverization. Besides, the produced CR has already been partly devulcanized after UHPWJ pulverization, and polymer degradation occurred in the meanwhile.