Liquefied wood (LW) is a naturally based product which has the potential to beused as an adhesive. It can be used as a part of a polymer formulation, as apart of an adhesive mixture with commercial adhesives, or as an independent material for wood bonding. In this study, wood was liquefied at 180°C using ethylene glycol as the solvent and sulphuric acid as a catalyst. In the first part of research, LW with different pH values was used for the bonding of solid wood at 200ŽŽC for 15 min. In the second part, LW with an optimal pH value was used for bonding at different press temperatures for 15 min. In the third part, the minimum pressing time at the optimal pH value and at the optimal press temperature was determined. Unmodified LW with a negative pH value, a press temperature of 180°C, and a pressing time of 12 min was determined to be optimal (based on highest shear strength) for the bonding of 5 mm thick wood lamellas with the LW used in this study. At these conditions bonds exhibited shear strength of around 7N/mm2 which was too low to attain standard requirements. Despite this, high wood failure (100%) was observed as a consequence of low pH value and high press temperature which caused damage of the part of beech lamellas where LW was applied.
COBISS.SI-ID: 2034057
We investigated secondary changes in beech bark, which is gaining increasing attention as a raw material for various uses. The structure and secondary changes in the bark could be precisely identified by means of a combination of light microscopy, transmission electron microscopy and UV-microspectrophotometry. Non collapsed phloem which is transporting assimilates undergoes secondary changes characterized by a collapse of sieve tubes, inflation of axial parenchyma, and development of sclereids. Sclereid cell walls are thick and poly-lamellated and have similar spectral characteristics but distinctly higher UV absorbance values than xylem fibers.
COBISS.SI-ID: 1942153
The objective of this research was to investigate the effect of liquefied wood (LW) on the cure kinetics and network properties of melamine–urea–formaldehyde (MUF) resins by differential scanning calorimetry. The MUF/LW compounds exhibited two distinct cross-linking processes. It can be assumed that there did not appear to be a coreaction of the MUF with the LW. The overall apparent activation energies (E a) of the curing reactions were calculated using the Kissinger equation. An nth-order kinetic model was used to describe the cross-linking of MUF/LW compounds, of various compositions, cured at different heating rates. The E a values for the cross-linking process of the MUF/LW compounds predominantly tended to be approximately 80 and 71 kJ mol−1 for MUF and LW, respectively. The apparent reaction orders of the MUF cross-linking process of the MUF/LW compounds were in the range 1–2, whereas the n values of the LW were approximately unity or less, which hints to there being a more complex mechanism of this process.
COBISS.SI-ID: 2049161
Liquefied wood is of a dark-brown to black colour, what is limiting its applications, for instance in coatings. In the paper, we were among the first ones or even the first, who showed that liquefied wood can be discoloured by a proper selection of the hydrogen based activated system.
COBISS.SI-ID: 2064777
Wood is one of the most important construction materials. In Slovenia spruce wood is most commonly used in construction. Spruce wood does not have sufficient natural durability and thus must be properly protected. Unfortunately, spruce wood is not very susceptible to impregnation. We have investigated the effect of different fungi on the impregnability of spruce wood through different periods of exposure to fungi, and the resulting changes in the strength of the wood. Specimens were exposed to three different fungi for three different periods of time. Weight loss, preservative penetration, and compression strength were determined. Measurements have shown a 126,4 % ± 23,3 % increase of Silvanolin® penetration in moist specimens, when exposed to H. fragiforme for 15 days and treated with vacuum-pressure system, and a 325,5 % ± 331,5 % increase of Poligen® WE 1 penetration in moist specimens, treated in the same conditions. Compression strength remained unaffected. In this research it was shown that different fungi can dissolve encrusted pit membranes and thus improve preservative penetration into spruce wood, and keep the desired compression strength simultaneously.
COBISS.SI-ID: 1987209