Devulcanization of ethylene–propylene–diene waste rubber by microwaves and chemical agents

Extensive use of rubber in industrial articles and their eventual disposal at the end of their useful service life has created a major concern for the environment. In automotive applications, ethylene–propylene–diene rubber (EPDM) is used to manufacture various parts which will be difficult to dispose of or scrap. A microwave oven was used as a heating source, and with the aid of some chemical agents and aromatic and aliphatic oils, cured EPDM waste powder was devulcanized at temperatures ranging from 200°C to 260°C. The devulcanized waste powder was then revulcanized with a sulfur cure system and its cure and mechanical properties were measured.

It emerged that with the aid of the chemical agents, the waste powder devulcanized more efficiently in the aromatic oil than it did in the aliphatic one. The chemical agents had different effects on the devulcanization of the waste powder and mechanical properties of the revulcanized compound. In addition, devulcanization was more efficient at higher temperatures. The hardness, tensile strength, and elongation at break of the revulcanized compounds were in the range of 49–79 Shore A, 2.0–3.7 MPa, and 34–211%, respectively. These properties were influenced mainly by the composition and devulcanization conditions of the waste powder. There is scope to recycle and reuse some of these compounds in automotive applications.