WOOD RESEARCH Volume 68, Number 2, 2023
VLADIMÍR IHNÁT and HENRICH LÜBKE

Water retention of beech shavings heat-treated at lower temperatures

Water retention after 2 hours and 24 hours of soaking in water was determined for beech shavings subjected to heat treatment at temperatures of 120°C, 140°C and 160°C for 2 hours, 4 hours, 6 hours and 8 hours in order to reduce the equilibrium moisture content (EMC) of the wood shavings for use in wood based composites. EMC was determined after 14 days of air conditioning at 23°C and 55% relative humidity. The measured values were compared with the sample dried at 103°C. Water retention was determined after 15 min of centrifugation at 1400 rev.min-1 for a more objective assessment of the wood’s ability to retain water in the cell lumens. The results showed that heat treatment reduces the EMC of beech shavings heat-treated at 160°C for 8 hours in the given conditions from 8.7% to 6.19%. The reduction of EMC at lower temperature was not sufficient enough, especially in the shorter treatment duration of up to 6 hours. In parallel, the reduction of water retention from 65.53% to 47.79% was caused by heat treatment for 8 hours at 160°C.

WOOD RESEARCH Volume 61, Number 3, 2016
Mehmet Yeniocak, Mehmet Colak, Osman Goktas, and Ibrahim Koca

Fire resistance performance of wood materials colored with eco-friendly pomegranate skin (Punica granatum) extracts

The main goal of this study was to determine fire resistance properties of wood treated with pomegranate extract and mordant mixes. According to that wood materials Scotch pine (Pinus sylvestris L.), Oriental beech (Fagus orientalis Lipsky) were chosen. Aluminum sulphate (KAl2(SO4)3.18H2O) copper sulphate (CuSO2.5H2O) and vinegar were used as mordant agent and a synthetic dye was used for comparison. Ultrasonic assisted method were used for extractionthe plant dyestuff from pomegranate skin (Punica granatum) and then applied to wood blocks by immersion (classic) and immersion ultrasonic assisted methods. The combustion test was realized according to ASTM-E 69-02 (2002) standard. The mass losses release of gasses (CO, O2) and the temperature differences of samples were detected for each 30 seconds during combustion. The results showed that the aluminum sulphate mixes were showed the best results on all tests. Unfortunately test performances are not enough to retard the fire effect on the wood materials. Eco-friendly natural colorant might be developed to use them as fire retardant.

WOOD RESEARCH Volume 62, Number 2, 2017
Martin Sviták and Daniel Ruman

Tensile-shear strength of layered wood reinforced by carbon materials

This article deals with the influence of selected factors (wood species, used adhesive type, carbon reinforcement) on tensile-shear strength of glued layered wood. Tensile-shear strength was investigated on samples of European beech (Fagus sylvatica L.) and European spruce (Picea abies L.). The laminated wood was modified with carbon polymer or carbon fabric, and the tensile-shear strength values were compared with non-reinforced wood. Polyurethane and epoxide adhesives were used for the experiment. The highest tensile-shear strength values were found on non-reinforced beech wood glued by epoxide adhesive. As far as the tensile-shear strength concerns, each monitored factor as well as their mutual interactions were proven to be statistically significant.

WOOD RESEARCH Volume 63, Number 6, 2018
Jozef Kúdela, Ivan Kubovský, and Michal Andrejko

Impact of different radiation forms on beech wood discolouration

This study analyses beech wood surface discolouration induced through UV radiation during an accelerated ageing process and with radiation emitted from a CO2 laser beam operating under specific settings. The results show that the extent of beech wood surface discolouration was dependent on the amount and the type of the energy delivered and on the absorption performance of the main wood components. It was observed that increasing irradiation dose caused decreasing wood surface lightness in both UV radiation and CO2 laser-produced radiation scenarios. In most cases, the values of colour coordinates a* and b* increased, and the wood surface was gradually turning dark brown. At high irradiation doses from the CO2 laser, there were recorded decreasing trends in a* and b*, and the beech surface darkened substantially (up to black). To attain purpose-oriented wood surface discolouration under specific modification modes, there is necessary to carry out thorough chemical analyses of the treated wood surface and to express quantitatively the dependence between the energy supplied, colour, adsorption capacity of the main wood components and the ongoing chemical changes.

WOOD RESEARCH Volume 64, Number 5, 2019
Tatiana Vilkovská, Ivan Klement, and Igor Čunderlík

Longitudinal contraction of reaction and opposite wood during drying process

Reaction beech wood has different anatomical and also chemical characteristics than normal (opposite) wood. The difference in density is conditioned by percentage of G–layer. Fibers cells in reaction beech wood have a different cell wall structure and a different chemical composition, as well. Longitudinal contraction was noticeable in reaction (tension) samples, where it was several times higher, what could be expected considering the physical properties of reaction beech wood. Our measurements confirmed that drying time has remarkable effect on longitudinal contraction. Higher longitudinal contraction was measured in temperature 60°C and 120°C, which had almost identical drying time. The issue of variability initial moistures did not affect the drying process and samples reached approximately equal final moisture content. Reaction beech wood is a very serious problem in nowadays wood production.

WOOD RESEARCH Volume 64, Number 3, 2019
Pažitný Andrej, Albert Russ, Boháček Štefan, Monika Stankovská, VLADIMÍR IHNÁT, and Štefan Šutý

Various lignocellulosic raw materials pretreatment processes utilizable for increasing holocellulose accessibility for hydrolytic enzymes Part II. Effect of steam explosion temperature on beech enzymatic hydrolysis

Beech wood is one of the most abundant species and the most harvested hardwood in Slovak Republic. The structure and chemical composition predetermines beech wood for the second generation bioethanol production. Steam explosion of beech wood from industrial treatment was investigated as a suitable pretreatment method. The effect of steam explosion temperature on beech sawdust enzymatic hydrolysis was investigated. Optimum steam explosion temperature at around 180°C was determined based on concentration of monosaccharides in hydrolysates and concentration of enzymatic hydrolysis inhibitors such as formic acid and acetic acid from beech sawdust. This corresponds to creating conditions resulting in good disintegration to the lignocellulosic structure which leads to increased cellulose accessibility. Non-treated beech sawdust does not enable sufficient cellulose accessibility while excessively high temperature results in significant breakdown of monosaccharides and lignin and formation of inhibitors. The concentration of inhibitors was also determined for each studied steam explosion temperature. Based on steam explosion of beech sawdust, the effect of severity factors was investigated to find the optimum conditions of steam explosion pretreatment on cellulose and xylan recovery of beech wood. The obtained optimum steam explosion temperature corresponds to severity factor R0 = 3.36 (180°C, 10 minutes).