Izguba mase termično modificiranega lesa in njegova odpornost proti lesnim glivam : diplomsko delo - univerzitetni študij

Šušteršič, Žiga (author), Pohleven, Franc (mentor), Humar, Miha (reviewer)

Termična modifikacija lesa povzroči v oleseneli celični steni vrsto kemijskih sprememb, ki izboljšajo dimenzijsko stabilnost in odpornost lesa proti glivam, poslabšajo pa nekatere mehanske lastnosti. Les rdečega bora smo termično modificirali v prisotnosti dušika pri temperaturah 220 °C, 240 °C in 250 °C. Po koncu modifikacije smo vzorcem z gravimetrično metodo določili izgubo mase. Z mini blok testom smo ugotavljali odpornost modificiranega lesa proti beli hišni gobi (Poria placenta). Z metodo GC-MS smo spremljali kemijske spremembe v lesu med modifikacijo in po njej. Analizirali smo vsebnost C, H in O ter izračunali razmerje O/C. Ugotovili smo, da so izgube mase večje pri višji temperaturi in daljšem času modifikacije. Odpornost lesa se s stopnjo modifikacije povečuje. Pri 15 % izgubi mase so bili vsi vzorci popolnoma odporni proti glivi, ne glede na temperaturo. Vzrok izboljšanja odpornosti je razgradnja glavnih lesnih komponent, predvsem hemiceluloze, ki je glivam glavni vir hrane. Posledica termičnega razkroja je zmanjšanje deleza O/C po modifikaciji. Razmerje O/C se spreminja linearno s stopnjo modifikacije, kar omogoča posredno določanje izgube mase.

• Language: Slovenian
• Keywords: les, rdeči bor, termična modifikacija, odpornost, lesne glive, razmerje O/C
• Work type: Undergraduate thesis
• Typology: 2.11 - Undergraduate Thesis
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: [Ž. Šušteršič]
• Year: 2009
• Number of pages: X, 36 f., [5] f. pril.
• PID: 20.500.12556/RUL-451
• UDC: 630*84
• COBISS.SI-ID: 1778569
• Publication date in RUL: 11.07.2014

Secondary language

• Language: English
• Title: Mass loss of thermally modified wood and its resistance against wood decay fungi : graduation thesis - university studies

Abstract

Thermal modification of wood causes several chemical changes in wood cell walls, leading to improvement of dimensional stability and durability against fungal attack, and a decrease of some mechanical properties. Scots pine (Pinus sylvestris) samples were thermally modified in nitrogen atmosphere at 220 °C, 240 °C and 250 °C. After modification, the samples were weighed to determine mass loss. A small block test was used to test durability against white rot fungi (Poria placenta). Using GC-MS, the chemical changes occurring during thermal modification were observed. C, H and O content variation was analyzed, and O/C ratio calculated. The results show positive correlation among mass loss, temperature and time of heat treatment. Wood durability is in positive correlation with the degree of modification. The samples with 15 % mass loss were completely resistant against the fungus, irrespectively to temperature. The reason for better durability is degradation of main wood components, mainly hemicellulose, the main nutrient for fungal growth. Thermal degradation decreases O/C ratio. This value is in linear relationship with the degree of modification, allowing the determination of mass loss indirectly.

• Keywords: wood, Scots pine, thermal modification, resistance, wood decay fungi, O/C ratio