The Study on the Mechanical Properties of the De-Vulcanized Waste Rubber by a Mechanical Technique

Recycling of waste rubbers is developing due to environmental concerns and continuous increasing raw materials price. The EPDM (ethylene-propylene-diene rubber) rubber is the rubber base of the non tire automotive rubber articles and their recycling is necessary for resources saving and the environment protection. A mechanical recycling technique, a twin screw extruder with the aid of a de-vulcanizing agent, TMTD (tetramethylthiuram disulfide) was used to de-vulcanize waste rubber powder from discarded EPDM automotive parts. The de-vulcanized rubbers, subsequently, re-vulcanized in a semi-efficient (SEV) curing system and correspondent curing and mechanical properties including hardness, tensile strength and elongation at break were measured and the results were compared and discussed. The results showed that the waste rubber de-vulcanized with used technique efficiently. The direct relationship was observed between increasing de-vulcanization percent and also the crosslink density reduction of the waste cured rubbers with improving the curing and mechanical properties of re-vulcanized compounds. The optimum de-vulcanization operating conditions were obtained by a design of experiment software at rotor speed of 180 rpm at a constant operative temperature, 220 . The main challenge for using the outcomes of this study in commercial scale was the difference between waste rubbers composition because they provided from various sources.