Devulcanization of ethylene‐propylene‐diene monomer rubber waste. Effect of diphenyl disulfide derivate as devulcanizing agent on vulcanization, and devulcanization process

Abstract

A systematic study was performed to understand the effects of the devulcanizing agent dibenzamido diphenyl disulfide (DBD) on the vulcanization and devulcanization process of a sulfur‐cured ethylene‐propylene‐diene monomer (EPDM) rubber. The influence of DBD on vulcanization was investigated by mixing DBD with virgin rubber and curative system. The devulcanization of rubber waste was achieved with varying amounts of DBD ranging from 0.4 to 13.8 wt% and temperatures from 150 to 200°C. The quality of vulcanizates and devulcanizates was evaluated by rheometer tests, temperature scanning stress relaxation measurements, and analysis of mechanical properties. During vulcanization, DBD acts as an accelerator in the presence of sulfur. When accelerators are added, the scorch time increases, and the cure rate decreases. Thus, DBD acts as a retarder. In the presence of activators, DBD leads to a significant reduction of crosslink density. This results in composites with high elongation at break and poor compression set values. The efficiency of the devulcanization of rubber waste depends strongly on DBD concentration and temperature. The monosulfidic crosslinks are cleaved by low concentrations of DBD, while polysulfidic crosslinks require higher concentrations. These results show that DBD is effective as a devulcanizing agent and degrades the network below 200°C.

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

“…The initial torque level of the isothermal rheometer curves confirm the storage modulus values (Figure 1b). P2 and P3 devulcanized at 120°C show compared to the other samples a sharp drop at the beginning of the curves which relates to the network degradation reaction of DBD 39 . Whether polymer or crosslink scission occurs cannot be determined from the results, it can however be assumed that crosslink scission happens since EPDM has a saturated backbone.…”

“…Meyer GmbH) originated from post‐industrial waste generated during the production of sealing systems. The particle size of EPDM RWP is smaller than 1 mm 39 . The main components are EPDM rubber Keltan 9650Q®, paraffin oil 500 MSN, and carbon black type N550, which are used to make the reference material with a sulfur‐based curing system.…”

“…The main components of the RWP are EPDM rubber, paraffinic oil, and carbon black. The rubber in the RWP is about one third, 39 and the curing system was not adjusted for possible residues in the RWP. The composition of the RWP resembles that of the reference.…”

“…The first is important to produce a new product, and the second is a key step to obtaining a useful product. The process parameter and especially the concentration of devulcanizing agents influence the chemistry and the kinetics of the revulcanization process 39 . Studies about the influence of the devulcanizing agent residues in recyclate on the revulcanization process and their relationship with the mechanical properties of the composite materials are lacking.…”

Recycling NR/SBR waste using probe sonication as a new devulcanizing method; study on influencing parameters

“…Diphenyl disulde (DPDS) were used as a conventional and effective chemical devulcanizing agent at 1.2 phr [38][39][40] in this study. It was added directly to the NR/SBR powder on a two roll mill.…”