Devulcanization of Sulfur-Cured EPDM: A Critical Review of Selective Crosslink Scission, Its Measurement, and Continuous Processing
- 1Exterior & Closure Materials Development Team, Hyundai Motor Company, Hwaseong-si 18280, Republic of Korea
- 2Sustainable Materials R & D Center, Korea Automotive Technology Institute, Cheonan-si 31214, Republic of Korea
Abstract
Sulfur-cured ethylene–propylene–diene monomer (EPDM) sealing scrap cannot be melt-reprocessed; devulcanization recovers rubber only if it cuts crosslinks selectively. This review separates EPDM-direct findings from tire, natural rubber (NR) and styrene–butadiene-rubber transfers. Metrics have converged on swelling, crosslink density, sol fraction, Horikx selectivity analysis, and a rheological proxy, without a grading standard. Two EPDM studies favored milder temperatures; extrusion selectivity depended jointly on thermal profile and screw speed, and excessive severity can cause re-crosslinking. Thermomechanical and agent-assisted extrusion have run continuously on EPDM in more than one laboratory; one group’s agent-assisted devulcanizate met the tensile, compression set and hardness limits of a non-automotive seal specification, the last two only after blending with 25 wt% virgin rubber. In the only direct comparison, ethylidene-norbornene EPDM was much less reactive toward disulfides than NR, which its authors attribute to a denser, more monosulfidic network less prone to main-chain scission. A single EPDM process life cycle assessment (LCA) identifies energy as the main environmental lever. The review contributes maturity classes, scission pathways labeled proposed or demonstrated, and a minimum LCA reporting set. Closing five EPDM-direct gaps (grading standards, green-route data, in-line selectivity sensing, joint throughput–energy–quality reporting, feedstock sorting) would make continuous agent-assisted extrusion a specifiable route.
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BibTeX
@article{nam2026devulcanization,
title = {{Devulcanization of Sulfur-Cured EPDM: A Critical Review of Selective Crosslink Scission, Its Measurement, and Continuous Processing}},
author = {Ki-Dong Nam and Yeon-Jee Cho and Ho-Dong Kim and Jeong-Hwan Yoon},
journal = {Polymers},
year = {2026},
month = oct,
doi = {10.3390/polym18202477},
url = {https://www.mdpi.com/2073-4360/18/20/2477},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Devulcanization of Sulfur-Cured EPDM: A Critical Review of Selective Crosslink Scission, Its Measurement, and Continuous Processing
AU - Ki-Dong Nam
AU - Yeon-Jee Cho
AU - Ho-Dong Kim
AU - Jeong-Hwan Yoon
PY - 2026
DA - 2026/10/01
JO - Polymers
DO - 10.3390/polym18202477
UR - https://www.mdpi.com/2073-4360/18/20/2477
AB - Sulfur-cured ethylene–propylene–diene monomer (EPDM) sealing scrap cannot be melt-reprocessed; devulcanization recovers rubber only if it cuts crosslinks selectively. This review separates EPDM-direct findings from tire, natural rubber (NR) and styrene–butadiene-rubber transfers. Metrics have converged on swelling, crosslink density, sol fraction, Horikx selectivity analysis, and a rheological proxy, without a grading standard. Two EPDM studies favored milder temperatures; extrusion selectivity depended jointly on thermal profile and screw speed, and excessive severity can cause re-crosslinking. Thermomechanical and agent-assisted extrusion have run continuously on EPDM in more than one laboratory; one group’s agent-assisted devulcanizate met the tensile, compression set and hardness limits of a non-automotive seal specification, the last two only after blending with 25 wt% virgin rubber. In the only direct comparison, ethylidene-norbornene EPDM was much less reactive toward disulfides than NR, which its authors attribute to a denser, more monosulfidic network less prone to main-chain scission. A single EPDM process life cycle assessment (LCA) identifies energy as the main environmental lever. The review contributes maturity classes, scission pathways labeled proposed or demonstrated, and a minimum LCA reporting set. Closing five EPDM-direct gaps (grading standards, green-route data, in-line selectivity sensing, joint throughput–energy–quality reporting, feedstock sorting) would make continuous agent-assisted extrusion a specifiable route.
SN - 2073-4360
ER -