Dresden 2020 – scientific programme

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BP: Fachverband Biologische Physik

BP 3: Biopolymers, Biomaterials and Bioinspired Functional Materials (joint session CPP/BP)

BP 3.7: Talk

Monday, March 16, 2020, 11:00–11:15, ZEU 114

Viscoelastic AFM characterization of the S2 layer of wood pulp fibers — •Caterina Czibula^1,3, Christian Ganser^1,3, Tristan Seidlhofer^2,3, Ulrich Hirn^2,3, and Christian Teichert^1,3 — ¹Institute of Physics, Montanuniversitaet Leoben, Austria — ²Institute of Paper, Pulp and Fibre Technology, TU Graz, Austria — ³CD Laboratory for Fiber Swelling and Paper Performance, TU Graz

Wood fibers consist of several cell wall layers which differ in thickness, chemical composition, and alignment of cellulose microfibrils. The S2 layer is the thickest layer, and dominates the mechanical behavior of the fibers. Several investigations with depth-sensing methods have so far focused on the characterization of the mechanical properties of the S2 layer. However, studies on the influence of relative humidity (RH) and the viscoelastic behavior of this layer are still missing. This work focusses on the viscoelastic behavior of the S2 layer at different RH by implementing an atomic force microscopy (AFM) based method. Here, wood pulp fibers have been prepared by microtome cutting, and a possible penetration of the embedding material in the cell wall layers has been ruled out by Raman spectroscopy. The evaluation of the experimental AFM data combines contact mechanics and viscoelastic models. It will be demonstrated that the Generalized Maxwell model yields reasonable results for the S2 layer measured at different RH. With increasing RH, the S2 layer shows a decrease in elastic and viscous parameters. The effect of different load rates will be discussed, and the viscoelastic results will be compared to AFM based nanoindentation data.