Mechanochemical devulcanization of EPDM rubber waste. Correlation of process parameters with sol–gel analyses and revulcanization properties

• Published in: Journal of applied polymer science 2023-05, Vol.140 (17), p.n/a
• Main Authors: Gschwind, Larissa, Jordan, Carmen‐Simona, Vennemann, Norbert, Susoff, Markus L.
• Format: Article
• Language: English
• Subjects: Degradation; devulcanization; EPDM rubber waste; Materials science; Mechanical properties; Polymers; Process parameters; properties; Propylene; recycling; Rubber; Sol-gel processes; sol–gel analysis; Tensile strength
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.53768

Ethylene–propylene–diene rubber (EPDM) scrap was devulcanized in an internal mixer with varying amounts of dibenzamido diphenyl disulfide (DBD) at temperatures below 200°C. The devulcanization effect and sol–gel analyses of the devulcanizates, and the mechanical properties of the sulfur‐cured revulcanizates were studied. Residual DBD was still present in the sol at 160°C and degraded DBD at 200°C. DBD affects the curing leading to poor properties. So, the temperature must be adjusted according to the DBD concentration to obtain a superior recyclate for sealing systems. At 0.4 wt% DBD, the degradation reaction was already complete at 120°C, but only 52% and 61% of the tensile strength σ and strain at break ε of the virgin material were achieved. At 160°C and 2 wt%, the degradation reaction was complete, and the DBD effect on properties was small; 65% and 86% of σ and ε were recovered, respectively. To prevent property degradation, 200°C was required at 3.9 wt% DBD, resulting in 97% and 95% of σ and ε, but only 70% of hardness. Ethylene–propylene–diene rubber (EPDM) waste was devulcanized with dibenzamido diphenyl disulfide (DBD) below 200°C in an internal mixer. Chemical analyses of the devulcanizate were correlated with the mechanical properties of the revulcanizates and interpreted in terms of the devulcanization parameters. The DBD excess interacts with the curing system, resulting in poor properties. Thus, the DBD concentration and process temperature had to be adjusted to achieve properties suitable for reuse of the recyclate in sealing systems.