Primerjalna analiza površinskih lastnosti navadne in termično modificirane bukovine v procesu parjenja

Frlic, Zoran (author), Žigon, Jure (mentor), Kržišnik, Davor (comentor)

Namen magistrskega dela je bil proučiti vpliv parjenja lesa na površinske lastnosti navadne in termično modificirane bukovine (Fagus sylvatica L.). Ovrednotili smo vpliv stopnje termične modifikacije, temperature parjenja in začetne ravnovesne vlažnosti lesa na dinamiko segrevanja in navlaževanja ter na mehanske, kemijske in barvne lastnosti površine. Preizkušanci iz nemodificirane bukovine ter bukovine, termično modificirane pri 180 °C in 220 °C, so bili uravnovešeni pri 65 % in 85 % relativne zračne vlažnosti ter parjeni pri temperaturah 75 °C, 85 °C in 95 °C. Vlažnost lesa smo določili gravimetrično in z meritvami električne upornosti, mehanske lastnosti pa ovrednotili z metodo krožnega razenja, konfokalno lasersko mikroskopijo in metodo odtrgovanja pečatov. Kemijske spremembe smo analizirali z ATR-FTIR spektroskopijo, barvne pa v CIELAB barvnem prostoru. Termična modifikacija je zmanjšala higroskopnost lesa in povzročila izrazitejšo potemnitev z višanjem temperature modifikacije. Parjenje je povečalo vsebnost vlage v naravni bukovini za 3,3–3,4 %, pri lesu, modificiranem pri 180 °C, za 1,9–2,9 %, pri lesu, modificiranem pri 220 °C, pa za 1,1–1,6 %. Meritve z elektrouporovnimi senzorji so pokazale višjo ravnovesno vlažnost naravne bukovine kot termično modificiranega lesa, vendar razlik v dinamiki segrevanja in sprememb vlažnosti zaradi omejitev merilne opreme ni bilo mogoče zanesljivo ovrednotiti. Preizkus krožnega razenja je pokazal večjo občutljivost površin termično modificiranega in vlažnejšega lesa na mehanske poškodbe. Metoda odtrgovanja pečatov zaradi prevladujočih adhezijskih porušitev med lepilom in aluminijastim pečatom ni omogočila zanesljivega vrednotenja kohezijske trdnosti površinskih slojev lesa.

• Language: Slovenian
• Keywords: bukev (Fagus sylvatica L.), hidrotermična obdelava, les, površina, relativna zračna vlažnost, parjenje, termična modifikacija
• Work type: Master's thesis/paper
• Organization: BF - Biotechnical Faculty
• Year: 2026
• PID: 20.500.12556/RUL-187687
• Publication date in RUL: 13.09.2026

Secondary language

• Language: English
• Title: Comparative analysis of the surface properties of untreated and thermally modified beech wood during the steaming process

Abstract

This study investigated the effects of steaming on the surface properties of unmodified and thermally modified beech (Fagus sylvatica L.), with an emphasis on the influence of thermal modification intensity, steaming temperature, and initial equilibrium moisture content on moisture uptake, heating dynamics, and surface mechanical, chemical, and colour properties. Unmodified beech and beech thermally modified at 180 °C and 220 °C were equilibrated at 65% and 85% relative humidity and subsequently steamed at 75 °C, 85 °C, and 95 °C. Moisture content was determined gravimetrically and by electrical resistivity measurements, while mechanical properties were evaluated using scratch testing, confocal laser microscopy and peel strength. Chemical changes were analysed using ATR-FTIR spectroscopy, and colour changes were assessed in the CIE L*a*b* colour space. Thermal modification reduced the hygroscopicity of the wood and caused darkening as the modification temperature increased. Steaming increased the moisture content of unmodified beech wood by 3.3–3.4%, of wood modified at 180 °C by 1.9–2.9%, and of wood modified at 220 °C by 1.1–1.6%. Measurements using electrical resistance sensors showed a higher equilibrium moisture content in natural beech than in thermally modified wood; however, due to limitations in the measuring equipment, it was not possible to reliably assess differences in heating dynamics and moisture content changes. Scratch resistance testing revealed that the surfaces of thermally modified and moister wood were more susceptible to damage. Peel strength testing, due to predominant adhesive failures between the adhesive and the aluminium seal, did not allow for a reliable assessment of the cohesive strength of the wood surface layers.

• Keywords: European beech (Fagus sylvatica L.), hydrothermal treatment, wood, surface, relative humidity, steaming, thermal modification