In this paper, phenol-formaldehyde (PF) resins with different average molecular weight (Mw) oligomers were used, to evaluate the effect of molecular size on the allocation of impregnated chemicals in wood microstructure at different hierarchical levels (from wood tissue to single cell wall layers). Light microscopy (LM) and various other alternative instrumental methods, as UV microspectrophotometry (UMSP) and micro X-ray computed tomography (µXCT), have been used and to determine, as well visualize, the micro-distribution and penetration depth of resin into wood matter. Therefore, European beech wood (Fagus Sylvatica L.) blocks of 25x25x10 mm³ were vacuum impregnated with different molecular sizes at three aqueous solutions concentration of 9, 18 and 27%. Due to different procedure and physical back ground of methods, obtained micro-images passed certain level of image processing and comparison between methods were performed (Fig 1).
The presence of chemical agent in the wood, in terms of LM, was detected by way of their identification on the specimen cross-section as result of different intensity of safranin staining, but in UMSP, based on UV light absorbance at 278 nm by phe- nolic-based compounds. While, the incorporation of resin into wood can be measured and visualized by using µXCT, only based on porosity changes between one and the same volumes of interest (VOI) selected from one and the same sample before and after the treatment. Despite of so such distinctness between techniques, our results appears stronger or weaker positive correlation between the methods.
Based on roughly estimation of obtained results, might be that LM could be useful to give first expression (quantitative) on resin distribution into wood tissue and in some cases could substitute more complicated method as UMSP. Concerning to X-ray CT, our preliminary results shows, that it might be the promising technique to evaluate and visualize resin distribution into wood at different hierarchical levels and 3D.
Keywords: Phenol-formaldehyde resin, light microscopy, micro X-Ray CT, UMSP
Authors
Biziks V.
Wood Biology and Wood Products, Burckhard Institute, Georg-August University Göttingen, Göttingen, Germany
Bicke S.
Wood Biology and Wood Products, Burckhard Institute, Georg-August University Göttingen, Göttingen, Germany
Koch G.
Thünen-Institut, Hamburg, Germany
Van den Bulcke J.
UGCT – Woodlab-UGent, Laboratory of Wood Technology, Department of Forest and Water Management, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
UGCT, University of Ghent Center of X-ray Tomography, Ghent
Van Acker J.
UGCT – Woodlab-UGent, Laboratory of Wood Technology, Department of Forest and Water Management, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
UGCT, University of Ghent Center of X-ray Tomography, Ghent
Militz H.
Wood Biology and Wood Products, Burckhard Institute, Georg-August University Göttingen, Göttingen, Germany
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