Devulcanization and reuse of peroxide cured EPDM rubber for a greener world

Abstract: Waste management of vulcanized rubber is a serious environmental problem as the molecular structure formed during the process complicates recycling. Due to this, researchers have developed a process that can break the strong bonds and return the rubber to its original state. This process is called devulcanization and is developed for the tire industry due to the large amount of waste formed from this sector. This rubber is vulcanized with sulfurs like 90 % of other rubber products. However, there exist other products that are vulcanized with peroxides where much less research has been done. Due to this, it is unclear if devulcanization is possible as a different type of bond is formed in the vulcanization process. This work therefore investigates the possibilities with recycling by devulcanization of peroxide cured rubber where a collaboration is done with Roxtec International AB. The work also investigates the possibilities with reuse of the cooperating partner’s particular rubber and how everything can be implemented to understand the efficiency of these two waste management strategies and to share knowledge.  The used method for this work is a combination of the Participatory Action Research (PAR) and the Design thinking (DT) framework. A systematic literature review has also been conducted to collect relevant material for one of the research questions. The result showed that there exist many methods and possibilities with devulcanization of peroxides if sufficient energy is provided. However, the quality of the reclaimed rubber will be lacking as the bonds in the polymers main chain are degraded which affects the mechanical properties. Due to this only a small percentage can be reused by mixing it with virgin rubber. The efficiency for peroxides is therefore lower than for sulfurs. Regarding reuse many alternative usage areas were brainstromed but once the concepts were evaluated against the limitations with the material, the needs and the sustainability factor, only few solutions survived. The winning concept became a punching bag filled with granulated rubber crumbs. When investigating how everything can be implemented it turned out that a lot of effort is needed. For example, to get favorable results, the solution will require the punching bag company to also want to work towards sustainability by adapting take back systems. Devulcanization will then require that the waste is sorted which requires a big investment in both time and money to achieve. The conclusion of this work is that devulcanization and reuse is possible and the developed system solution can take care of parts of the waste. However, the possibilities are limited and to get rid of all the waste and develop a long-term solution that is both sustainable and further prepared for the future, more actions are needed. It is therefore of high interest to start investigating the possibilities with a new material that is easy to recycle or are degradable.