Investigation on wax-impregnated wood. Part 2: Study of void spaces filled with air by He pycnometry, Hg intrusion porosimetry, and 3D X-ray imaging

Abstract

The quantification of wax and remaining voids filled with air in wax-treated wood has not been described in detail in the literature, although such products are commercially available. In this paper, Scots pine (Pinus sylvestris L.) and beech (Fagus sylvatica L.) samples were impregnated with a hot melting amide wax and characterized. The apparent densities were measured with helium pycnometry and mercury intrusion porosimetry. The pore size distribution was determined by means of mercury intrusion porosimetry and samples were visualized with 3D X-ray tomography. The remaining void spaces were calculated based on the data of all three methods. The apparent densities range from 1.18 to 1.19 g cm-3 for treated pine and from 1.21 to 1.23 g cm-3 for treated beech. As a result of the wax impregnation, the pore volume decreases from 65–68% to 12–13% for pine and from 53–58% to 7–9% for beech. The pore size distribution shifts to smaller pores. The amount of the micropores measured by mercury intrusion porosimetry is overestimated. On the one hand, blocked large pores are compressed by the movement of wax deposits under high pressure during the mercury intrusion porosimetry (“movement-effect”). On the other hand, large pores remain inaccessible or are only accessible via smaller openings (“bottle-neck-effect”). Non-invasive 3D X-ray imaging detects such macropores but the size of the detected pores is limited by the given resolution of the method. Therefore, mercury intrusion porosimetry and X-ray tomography are complementary techniques.

Effect of thermo-hydro-mechanical densification on microstructure and properties of poplar wood (Populus tomentosa)

“…The pore characteristics of THM wood with CR75 showed that microcapillaries were created in cell walls, which made up the remaining minor pores and cracks. The results are consistent with those reported previously [37].…”

Effects of Moisture on Diffusion in Unmodified Wood Cell Walls: A Phenomenological Polymer Science Approach

“…Some of these cell wall porosity measurements were made in wood dried through solvent-exchange or supercritical CO 2 methods, which introduces cell porosity not present in unmodified dry wood [120,124,125]. Although Stone and Scallan concluded that unmodified wood cell walls are essentially non-porous in their nitrogen adsorption experiments [124], more recent mercury intrusion and helium pycnometry measurements report pore diameters as small as a few nanometers in a wide variety of wood species under dry conditions [126,127]. The more recent work claimed the small pores were in the wood cell walls.…”

X-ray computed tomography of wood-adhesive bondlines: attenuation and phase-contrast effects

“…7b) are narrower and show less overlap. Additionally, these images have not been filtered, and median filtering would help with image sharpness and clarity while preserving material edges Russ 2011;Scholz et al 2010).…”

“…Some studies have already demonstrated their effectiveness at generating contrast in various wood and fiber tomography analyses (Betz et al 2007;Mayo et al 2003Mayo et al , 2010. One recent study was even able to segment air, wood, and a low density, untagged wax in wood lumens from XCT data reconstructed with a phase retrieval algorithm (De Witte et al 2009;Scholz et al 2010). The QPR data shown in Fig.…”