Analyzing the effects of thermal stress on insulator papers by solid-state 13C NMR spectroscopy

Paul Jusner, Markus Bacher, Jonas Simon, Florian Bausch, Hajar Khaliliyan, Sonja Schiehser, Ivan Sumerskii, Elisabeth Schwaiger, Antje Potthast, Thomas Rosenau*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

15 Citations (Scopus)
37 Downloads (Pure)

Abstract

Million tons of cellulosic paper have been used for insulating coils in oil-filled electrical power transformers, thereby assuring the electricity supply for our societies. The high working temperatures in transformers constantly degrade paper insulators throughout their service life of up to 40 years. We approached the structural changes in oil-immersed cellulosic paper samples upon thermal stress in a study that compared unbleached softwood Kraft paper used as insulator paper with pure cotton cellulose paper. The model experiments used a thermal treatment in transformer oil at 170 °C for up to 14 days. The samples were characterized by means of 13C CP/MAS NMR spectroscopy, mainly based on deconvolution of the C4 resonance. An automated, fast, and reproducible C4 resonance deconvolution employing the “Peak Analyzer” tool of OriginPro 2020 (OriginLab Corporation, USA) was developed and used to exploit 13C CP/MAS NMR spectroscopy for the characterization of thermally stressed paper samples. Our results show that thermally induced structural changes depend heavily on the composition of paper, that hornification and coalescence of fibrils take place, and that the allomorph composition of cellulose crystallites is altered under the given conditions. Graphical abstract: [Figure not available: see fulltext.]

Original languageEnglish
JournalCellulose
Volume29
DOIs
Publication statusPublished - 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • Cellulose
  • Insulator paper
  • Paper aging
  • Solid-state C CP/MAS NMR spectroscopy
  • Solid-state structure
  • Thermal stress

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