Micromorphological studies of modified wood using a surface preparation technique based on ultraviolet laser ablation

Abstract

The objective of this paper is to demonstrate an ultraviolet (UV) laser ablation technique as a tool for sample preparation in microscopy studies of modified wood. Improved techniques for studying the microstructure of modified wood are crucial for a deeper understanding of many of their physical, mechanical and durability properties. The surface preparation technique is described in this paper. An illustration of micrographs of the micromorphology and polymer distribution in some examples of modified wood is also presented. It is clearly demonstrated that in contrast to conventional surface preparation techniques used for light microscopy and scanning electron microscopy, i.e. razor blade and microtome cutting techniques, UV laser ablation does not introduce any mechanically induced microcracks and redistribution of polymers or other mobile substances in the prepared surface. Results also show that, in particular, this technique seems to be suitable for studying polymer distribution in resin-impregnated wood, as well as detection of microcracks in modified wood cell walls.

Microstructure of chemically modified wood using X-ray computed tomography in relation to wetting properties

“…At the higher level of furfurylation (WPG 45%), even more tracheids are filled with furan polymers (Figure 1g) and the cell walls seem to be slightly thicker compared to those of pine furf28 . This is consistent with the finding of Wålinder et al (2009) concerning the higher filling ratio of lumens at higher WPG levels. Additionally, as illustrated in Figure 1h,i, the furfurylated tracheids are completely or partly filled.…”

“…For instance, acetylation was observed by electron microscopy (EM), and no evidence was found for cell wall damages or significant change in the microstructure (Sander et al 2003). In another scanning electron microscopy (SEM) study (Wålinder et al 2009), it was shown that some micro-structural changes may occur in situ polymerization during furfurylation, like polymer-filled lumen and microcracks in the cell walls. However, microstructural properties and remaining air-filled voids in acetylated and furfurylated wood samples are not yet quantified.…”

“…Mapping and visualization of these structural changes increase the understanding of the mechanism of chemical modification and facilitate the optimization of the modification parameters. Sander et al (2003), Kwon et al (2007) and Wålinder et al (2009) studied microstructural changes induced by chemical modification of wood. For instance, acetylation was observed by electron microscopy (EM), and no evidence was found for cell wall damages or significant change in the microstructure (Sander et al 2003).…”

Surface densification of acetylated wood

“…Previously, UV-laser ablation has been successfully used as a sample preparation technique for modified wood and wood-plastic composites (see e.g. Wålinder et al 2009;Laine et al 2014). …”

Reactive UV-absorber and epoxy functionalized soybean oil for enhanced UV-protection of clear coated wood

“…2. For more information regarding the UV excimer laser see literature [17]. Samples exposed to natural weathering were not analysed using SEM due to continued exposure, hence the samples needed to stay intact.…”