Reclaiming waste tire rubber by an irradiation technique

Abstract

Tire rubber recycling reduces production costs, saves resources, and decreases the environmental issues. Waste tire rubber were devulcanized by a laboratory microwave oven with the aid of the devulcanizing agent and the oil. The effect of several devulcanizing agents, hexadecylamine (HDA), Diphenyl disulfide (DPDS), N-cyclohexyl-2-benzothiozyl sulfenamide (CBS) 2-mercaptobenzothiazole disulfide (MBTS) and two types of the oils, aromatic and paraffinic with various contents in different irradiation temperatures was studied. For homogeneous devulcanization, the waste rubber was ground to a median particle size of 319 μm before further treatment and subsequent irradiation process. The results showed that used waste rubber powder was devulcanized effectively. Among of the devulcanizing agents and based on Horikx analysis, formulated compound with DPDS with the sol fraction, crosslink density (CLD) and devulcanization percent of 16.5%, 85 mol/m3 and 48%, respectively, was the most suitable compound for devulcanization when compared with formulated compounds with other devulcanizing agents. Among of compounds with different DPDS content, compound with 30 phr aromatic oil and 6 phr DPDS in formulation with devulcanization temperature of 240 °C, had the best devulcanizing parameters. Paraffinic oil had an adverse effect on devulcanization of the DPDS formulated compounds. For selected studied compounds, during microwave irradiation, a part or total amount of the polysulphides crosslinks were broken and the structure of the remained sulphur crosslinks were mostly mono sulphide. In the morphology study of the most devulcanized compounds, a coarse morphology of the non-devulcanized rubber covered by the devulcanized rubber were observed. The effect of the oil content was also obvious.