Sensitivity of offline and inline indicators for fiber stretching in continuous polyacrylonitrile stabilization

Research output: Contribution to journalResearch articleContributedpeer-review



In carbon fiber (CF) production, the stabilization process step is the most energy- and time-consuming step in comparison with carbonization and graphitization. To develop optimization routes for energy and productivity, the stabilization needs to be monitored continuously via inline analysis methods. To prognose the evolution of high-performance CF, the density of stabilized fibers has been identified as a robust pre-indicator. As the offline analysis of density is not feasible for inline analysis, a density-soft sensor based on the stabilization indices of Fourier Transform Infrared spectrum (FTIR)-analysis and Electron Paramagnetic Resonance (EPR) Spectroscopy could potentially be used for inline monitoring. In this study, a Polyacrylonitrile-based precursor fiber (PF) stabilized in a continuous thermomechanical stabilization line with varying stretching profiles was incrementally analyzed using density, FTIR-based relative cyclization index (RCI), and EPR-based free radical concentration (FRC). Our findings show RCI and EPR dependencies for density, correlated for RCI with sensitivity by stretching to cubic model parameters, while FRC exhibits linear relationships. Therefore, this study identifies two possible soft sensors for inline density measurement, enabling autonomous energy optimization within industry 4.0-based process systems.


Original languageEnglish
Article number68
Number of pages17
Issue number8
Publication statusPublished - 4 Aug 2023

External IDs

Scopus 85169077877
Mendeley 83cd10d4-fd61-30ad-be85-aefd53125241
ORCID /0000-0003-1370-064X/work/142243867
WOS 001057131500001


DFG Classification of Subject Areas according to Review Boards

Subject groups, research areas, subject areas according to Destatis


  • carbon fiber, polyacrylonitrile, cyclization, density, free radical concentration, stabilization

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