Hyperspectral imaging and chemometrics reveal wood acetylation on different spatial scales
- PDF / 3,409,300 Bytes
- 14 Pages / 595.276 x 790.866 pts Page_size
- 82 Downloads / 179 Views
Hyperspectral imaging and chemometrics reveal wood acetylation on different spatial scales Mikko Ma¨kela¨1,2,*
, Michael Altgen3, Tiina Belt3,4, and Lauri Rautkari3
1
VTT Technical Research Centre of Finland, Ltd, PO Box 1000, 02044 VTT Espoo, Finland Department of Forest Biomaterials and Technology, Swedish University of Agricultural Sciences, Skogsmarksgränd, 90183 Umeå, Sweden 3 School of Chemical Engineering, Department of Bioproducts and Biosystems, Aalto University, PO Box 16300, 00076 Aalto, Finland 4 Natural Resources Institute Finland (Luke), Tietotie 2, 02150 Espoo, Finland 2
Received: 30 October 2020
ABSTRACT
Accepted: 17 November 2020
Acetylation is a chemical treatment method commonly used to improve the hygroscopic properties of wood. Although acetylation has been industrially used for decades, its effects on the different hierarchical structures of wood are still poorly understood. In the laboratory, acetylation is generally measured gravimetrically. Weighing a sample before and after the modification procedure provides an indirect measure of the degree of acetylation within the entire sample but does not provide detailed information on the different structural regions of wood. Here, we determined acetylation of wood surfaces using hyperspectral near-infrared image regression. Our results show significant differences in the acetylation of earlywood and latewood, which suggests different durations for complete acetylation of earlywood and latewood cells. We have also illustrated our findings on the wood cell level based on the chemical differences in earlywood and latewood cell walls using cluster analysis of Raman images. These findings are an important step in understanding how chemical treatment affects the different hierarchical structures of wood on different spatial scales.
Ó
The Author(s) 2020
Handling Editor: Stephen Eichhorn.
Address correspondence to E-mail: [email protected]; [email protected]
https://doi.org/10.1007/s10853-020-05597-0
J Mater Sci
GRAPHICAL ABSTRACT
Introduction Wood structure, which is made up of cellulose fibrils embedded in a matrix of hemicelluloses and lignin, provides a high strength to weight ratio but makes wood vulnerable to hygroscopic changes and dimensional instability. These weaknesses can be compensated by various chemical and thermal treatments routinely used to improve wood properties for different applications. One alternative is wood acetylation, where acetic anhydride is used for replacing accessible hydroxyl groups (–OH) on wood polymers with acetyl groups (–CH3CO) generating acetic acid as a by-product [1]. Acetylation decreases the number of primary sorption sites for water molecules and limits the accessibility of unmodified hydroxyls due to the larger size of the acetyl groups [2, 3]. The degree of wood acetylation is generally measured gravimetrically by weighing a sample before and after the modification procedure. The obtained weight percent gain (WPG) provides an
indirect measure of acetylation of the entire sample and is highly co
Data Loading...
