Investigation of articifial weathering and decay resistance properties of polystrene and polycaprolaktone methods with modicication of wood

Biological degradation of lignocellulosic materials is one of the most important processes in nature. Growing microorganism activity in wood cause reduction of wood density, failure of mechanical strength and aesthetic quality which consequently negatively affects and lowers economic value of wood. On the other hand, it is known that UV-light sources degrade lignin on the surface of wood in a short time and wood becomes gray which is an undesirable feature. Traditional methods of wood conservatives and impreganation chemicals have long been used efficiently to protect wood from biodegradation, however many of those metal based chemicals have toxic effects and can be leached out from wood in time. In developing world, more effective, environmentally friendly and stable(unleachable) wood conservation methods are always needed. Some of the traditional wood impregnating agents are water or oil-based inorganic copper-, chromium-, arseniac-salts, boron derivatives, chlorinated chemicals, phenolics. Recently, especially environmental concerns and leaching problems cause the restriction to use conventional wood preservatives. The chemical modification of wood as an alternative wood protection method aim to react wood hydroxyl groups by the additional chemicals has growing in recent years in both laboratory studies and in industrial scale. Acetylation, furfurylation and dimethyloldihydroxylethyleneurea (DMDHEU) are chemical modification methods nowadays has commercial importance. On the other hand novel, more effective and cheaper methods and optimization of those studies are still needed. In this study, two different methods of chemical modification applied to Scotch pine to evaluate resistance to artificial weathering conditions and fungal decay. Already reported two new chemical modification methods via modification of spruce wood samples; polystyrene and polycaprolactone modification. The mentioned two modification methods were took place for the first time in the literature and indicate systematically that hydrophobic molecules and polymers can be impregnated in wood cell walls and reduce water uptake of wood (40-55%) and increased dimensional stability up to 40%. Also mechanical properties of the modified samples determined for the three methods by nanoindetation method. Modifications have no negative effect on mechanical properties, even modulus of elasticity increased (10%) for some methods, whereas the hardness also increased up to 15%. In this thesis, modified scots pine wood samples with polystyrene and polycaprolactone were exposed to fungal degradation tests in the laboratory to evaluate their durability; modified samples were also exposed to UV-light and water in an artificial weathering chamber to measure color changes of the surface, and changes in surface chemistry (ATR-FTIR), hydrophobicity (contact angle measurement), and the morphology (SEM), dimentional stability and water uptake rate were also investigated.