Reclaimation And Reuse Of Ground Rubber Powder

Large amounts of rubbers are used as tires for aeroplanes, trucks, cars, and shoes etc. But after a long run when these tires are not serviceable and discarded, only a few grams or kilograms of rubber (<1%) are abraded out. This poses two major problems: the wastage of valuable rubber and the disposal of waste tires leading to environmental pollution.In this paper two kinds of ground rubber powder (GRP) which are ground tire rubber (GTR) and ground tread leftover (GTL) had been reclaimed by low temperature chemical process (LTCP) and microwave reclaiming process (MRP). LTCP recycles GRP at room temperature with a novel chemical mixture which is capable of initiating proton exchange in a controlled manner and thereby open up the vulcanized network. The novel chemical mixture is made up of the zinc salt of dimethyldithiocarbamate and mercaptobenzothiazole in the presence of stearic acid, zinc oxide and sulphur. In the GTR reclaiming process, the influences of reclaiming agent content, carbon black content, softener content and vulcanization process had been studied. The results have shown that a compound of rubber: 100, accelerator: 1, ZnO:2, stearic acid:2, sulfur:2 for the fast curing system and a compound of rubber: 100, accelerator DM:3, accelerator D:2, accelerator ZDEC:1,ZnO:2, stearic acid:2, sulfur:3 for the slowly curing system obtained good physical properties. The tensile strength was greater than 8.5MPa which increased by 50% to general reclaimed rubber. The elongation at break was greater than 280%. The GTL reclaiming process needed much more time to get feasible viscosity, about 30～50min. The ratio of accelerator ZDMC/MBT is 1:4～1:3 and the amount of accelerator is 3 parts per hundreds of rubber (phr). The tensile strength was greater than 6.5MPa and the elongation at break was greater than 420%.The microwave devulcanization had also been used to reclaim these kinds of rubber waste. The devulcanization process of GTR was fast. The best devulcanization time was 160s, the tensile strength was greater than 8MPa and the elongation at break was greater than 470%. The devulcanizating process of GTL was slow. The best devulcanization time was 8min, the tensile strength was greater than 8.8MPa and the elongation at break was greater than 570%. The vulcanizating system of reclaimed rubber which came from industry had been researched. A compound of rubber: 100, accelerator DM:1, accelerator D:0.5, ZnO: 2.5, stearic acid: 1, sulfur: 1 had good physical properties. The tensile strength was greater than 8.5MPa and the elongation at break was greater than 450%. Application of deodorants about 7.5phr could improve the odor of reused rubber.The rheometric characteristics, mechanical properties and microstructures of reused rubber had been studied. There was a minimum point of the scorch time when reclaimed rubber's content was 50phr in three kinds of blending systems. When the amount of reclaimed rubber increased in blend, the curing times, curing degrees and mechanical properties decreased gradually. Reclaimed rubber/NR/BR blend and reclaimed rubber/SBR/BR blend with good performance had been prepared. The ratio of 85/15/5 in reclaimed rubber/SBR/BR blend had the best equilibrium between the physical properties of reused rubbers and economic benefit.Based on the SEM photos, reclaimed rubber made the fracture process smoothly. Yield process became shorter than new rubbers which made the products had poor mechanical properties.