**4. Conclusions**

The use of bio-based plasticizers (EESO, EECO), a conventional plasticizer (TDAE), and a synthetic plasticizer (Mesamoll®) in the compounding of NBR vulcanizates were studied. It was shown that bio-based plasticizers can advantageously be used as processing aids instead of conventional oils. Throughout the complete process chain, from preparation of the raw mixture and characterization of the kinetics of the crosslinking reaction to the final properties of the resulting elastomers, positive aspects of the use of bio-based plasticizers were observed, or at least a comparable level of the properties as for the use of mineral oil-based plasticizers. As an example, when using the bio-based plasticizers, there is a certain cure-accelerating effect, and also the crosslinking itself seems to be influenced. The mechanical properties are, generally, a result of the network development during vulcanization, and an improvement or at least a constancy in these properties is one of the main aims of material development. Based on the results shown in this paper, it can be concluded that for the investigated polymers, the use of such sustainable products is possible without noticeable loss in property levels. Future work will focus on other technical elastomers and on understanding of the influence of the plasticizer on the network development.

**Author Contributions:** Conceptualization, M.M.R. and K.R.; methodology, M.M.R. and K.O.; sample and specimen preparation, M.M.R.; experiments and analysis, M.M.R.; writing—original draft preparation, M.M.R.; writing—review and editing, M.M.R., K.R., K.O. and B.L.; supervision, K.O., K.R. and B.L.; project administration, K.R. and B.L.; funding acquisition, K.R. and B.L.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the German Federal Ministry of Education and Research (BMBF) in the framework of the ZIM project: ZF4429401SL7.

**Acknowledgments:** The authors thank the Federal Ministry of Education and Research (BMBF)for financial support in the framework of the ZIM project: ZF4429401SL7. We would like to thank Glaconchemie GmbH for their bio-based plasticizer supply. Further, we thank Lanxess Deutschland GmbH for supplying the Mesamoll®.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
