Date on Master's Thesis/Doctoral Dissertation

5-2023

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemical Engineering

Degree Program

Chemical Engineering, PhD

Committee Chair

Willing, Gerold

Committee Co-Chair (if applicable)

Berson, R. Eric

Committee Member

Berson, R. Eric

Committee Member

Watters, James

Committee Member

Rockaway, Thomas

Author's Keywords

chloramine; devulcanization; rubber; carbon black

Abstract

The disposal of waste rubber, particularly tire rubber, continues to pose a challenge in the 21st century. As a result, most end-of-life tires (ELTs) are either dumped in landfills or burned as tire-derived fuel. Chloramine devulcanization may offer a viable solution to this problem. Chloramine devulcanization is a low-temperature, low-pressure, process that selectively breaks sulfur crosslinks while preserving the polymer backbone. Chloramine devulcanization enables the recovery of chloramine recovered carbon black (CrCB) and devulcanized rubber (CdR) as separate products. Initial analysis of CdR revealed that it was formable and malleable, suggesting that crosslinking was absent. Spectroscopy showed that CdR contained alkanes, alkenes, and aromatic groups, and double-bonded carbon functional groups, indicating that it could be revulcanized into new rubber compounds. Further analysis shows that the breakup of the rubber matrix into CrCB and CdR involves the diffusion of chloramine between carbon black aggregates, where most sulfur crosslink breakage occurs in gaps between these aggregates. This leads to crack propagation and the formation of small CrCB particles that break away from the larger rubber particle in solution. Use of CrCB as a replacement for virgin carbon black in rubber applications was also studied. Although CrCB demonstrated a decline in reinforcement against an N550 control, it showed consistent performance compared to the N650 carbon black control in dock fender applications. This suggests that CrCB could be appropriate for replacing virgin carbon black in certain rubber applications where N650-N990 carbon black is used. Overall, chloramine devulcanization has the potential to promote rubber sustainability.

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