Scots pine sapwood (Pinus sylvestris L.) and beech (Fagus sylvatica L.) were impregnated with five waxes. The experiments indicate deep penetration into pine sapwood. Besides the viscosity, an influence of the wax polarity is presumed. Wax penetrates pine wood deeply via the cross-section, but not sufficiently enough to impregnate longer construction elements. However, the radial wax uptake exceeds the uptake via the tangential orientation and guarantees complete soaking of the sapwood tissue. The lateral wax penetration within beech is quite low and irregular. In addition to the temperature, a prolonged process procedure is decisive for an increasing wax uptake. As such, beech wood vessel elements seem to be fully impregnable via the longitudinal surface after a longer process procedure.
The migration and deposition of hot melting wax in wax-treated wood is not described in detail in the literature, although such products are available on the market. In the present study, this topic was investigated based on pine sapwood (Pinus sylvestris L.) and beech (Fagus sylvatica L.). The behavior of three different waxes was studied by means of 2D X-ray measurements and scanning electron microscopy observations. The three waxes did not show distinct differences in their deposition patterns. An intensive wax deposition could be observed within the vessels, tracheids, and fibers. In P. sylvestris the ray tracheids were penetrated with hot melting waxes, therefore there is a lateral wood penetration from the outer to the inner wood. In general, no wax penetration was visible within the parenchyma tissue and epithelium cells. Cracks were detected within the wax deposits as well as secondary microcapillaries, which were visible between the deposits and the cell walls.
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.
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