Article

Cellulose

, Volume 17, Issue 2, pp 231-243

First online:

Carbon-13 solid state NMR investigation and modeling of the morphological reorganization in regenerated cellulose fibres induced by controlled acid hydrolysis

  • Roger IbbettAffiliated withChristian Doppler Laboratory for Fibre and Textile and Chemistry in Cellulosics, University of ManchesterSchool of Biosciences, Division of Food Sciences, University of Nottingham Email author 
  • , Dimitra DomvoglouAffiliated withChristian Doppler Laboratory for Fibre and Textile and Chemistry in Cellulosics, University of Manchester
  • , Franz WortmannAffiliated withChristian Doppler Laboratory for Fibre and Textile and Chemistry in Cellulosics, University of Manchester
  • , K. Christian SchusterAffiliated withLenzing AG, Innovation and Business Development Textiles

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Abstract

CPMAS carbon-13 NMR has been used to follow structural changes affecting regenerated cellulose fibres during hydrolysis by mineral acids. The C4 envelope of regenerated cellulose was deconvoluted into separate peaks, for ordered (crystal), part-ordered (surface) and disordered (non-crystal) polymer, which allowed calculation of average crystal lateral sizes, in good agreement with WAXD data. A geometrical model has been used to describe recrystallisation at lateral crystal faces, occurring within a disordered boundary surrounding the crystal interior. A one-dimensional relaxation-diffusion model has also been constructed, appropriate to the spinodal structure of lyocell. This has provided estimates of proton T relaxation times for pure crystalline (cellulose II) and non-crystalline cellulose, around 24 and 4.5 ms, respectively, at a 45 kHz B1 field. From the model, crystalline and non-crystalline regions in lyocell are estimated to each be around 2.5 nm thickness for a material of 50% crystallinity, consistent with the 2–3 nm dimensions derived from C4 peak devonvolution.

Keywords

Cellulose Carbon-13 NMR Regenerated fibres Recrystallization Structure Hydrolysis Acid Depolymerisation