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.
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 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.
Anatomical features for Prosopis kuntzei Harms were studied by light and scanning electron microscopy. The wood is mainly diffuse-porous with indistinct growth ring boundaries. Vessel diameter ranges between 11 to 193 μm. The thick-walled fibres average 1275 μm in length. Parenchyma bands are 66 to 1066 μm apart. Heartwood extractives were studied in the vessels, rays and part of the fibres by means of scanning UV microspectrophotometry. The pyrolitic lignin content is 30.7%. The percentage of polyphenolic compounds, such as flavonoids, hydrolysable tannins and proanthocyanidins, is comparatively high at 5.8%. Total extract contents were determined after organic solvent extractions (23.2%) and water extractions (24.9%). The FTIR spectroscopy showed nearly identical spectra for the methanol and water extracts, with characteristic absorption bands for aromatic substances at 1615 and 1520 cm-1. The spectrum of the acetone extract differs only due to an additional but distinct absorption in the carbonyl range at 1695 cm-1. GC/MS analyses revealed that in the acetone and methanol extracts, tetrahydroxy-flavan-3-ols (isomers of catechin and epicatechin) were the main constituents with a ratio of 25.3 and 27.6%.
Full impregnation of modified wood with waxAbstract Acetylated timber, thermally modified timber (TMT) and timber modified with dimethylol-dihydroxyethylenurea (DMDHEU) was impregnated with wax. Subsequently, the influence of hydrophobic wax deposits on the capillary water uptake and the strength properties of the pre-modified timber were investigated. The water uptake in longitudinal direction decreased to 0.03 kg·m −2 ·h −0.5 for acetylated timber and 0.13 kg·m −2 ·h −0.5 for TMT. In tangential direction it was reduced to 0.02 kg·m −2 ·h −0.5 (acetylated wood) and 0.05 kg·m −2 ·h −0.5 (TMT). Thus, water uptake of acetylated timber was lowered by a maximum of factor 28 in longitudinal and factor 9 in tangential direction. For TMT, water uptake was reduced by factor 12 in both directions. For both cases, the pre-modified material without wax treatment was measured as reference. The bending and impact bending strength of TMT increased by a maximum of up to 45% and 64%, respectively. The Brinell hardness perpendicular to the grain rose by up to 420%. Consequently, strength losses due to thermal modification were partly compensated by subsequent wax impregnation. The compression strength increased by up to 47% and the modulus of elasticity by up to 66% for acetylated timber. For the same material, the hardness perpendicular to the grain peaked at 109 N/mm 2 . The longitudinal water uptake of timber modified with DMDHEU decreased by a maximum of 45% after impregnation with wax, whereas Brinell hardness perpendicular to the grain increased by 150%. Besides diminished water uptake, a reinforcement of wood structure degraded after preceding modification can be accomplished by wax treatment.
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