Influence of microwave plasticization, high temperature treatment and areal compression on modulus of elasticity and bending strength perpendicular to the gain in radial direction at Spruce (Picea abies (L.) Karst.)

Abstract

MERENDA, L., NIKL, K.: Infl uence of microwave plasticization, high temperature treatment and areal compression on modulus of elasticity and bending strength perpendicular to the gain in radial direction at Spruce (Picea abies (L.) Karst.). Acta univ. agric. et silvic. Mendel. Brun., 2009, LVII, No. 5, pp. 205-212 Nowadays wood modifi cation is very-discussed and its importance is growing up. Wood plasticization alias a temporary change of wood properties makes subsequent processing possible. Plasticization is very suitable for subsequent mechanical compressing of wood. Instead steaming and boiling there is a microwave heating for wood plasticization. This kind of heating cuts down the time of plasticization from hours to seconds and also reduces energy consumption. Pressing of wood perpendicular to the gain in radial direction causes change of wood structure, increases wood density and due to this the wood has increased mechanical properties as bending strength and Young's modulus of elasticity. Modifi cated wood has many positive properties, but also has number of negative properties. The high-temperature treatment eliminates these negative proeprties to the large extend. The high temperature causes changes in chemical structure and reduces number of soprtion places. Due to this the wood has lower equilibrium moisture content. Moisture content greatly aff ects physical and mechanical properties. The wood that was treated by high temperature (200 °C) has lower moisture content coresponding to the equilibrium moisture content than the wood without high-tepmerature treatment (the wood only microwave plasticizated and mechanicaly compressed). Lower moisture content makes rising bending strength and Young's modulus of elasticity. The aim of this article is to compare bending strength perpendicular to the gain in radial direction and Young's modulus of elasticity of Spruce wood that was microwave, mechanical and modifi cated in high-temperature.Picea abies (L.) Karst., microwave plasticization, pressing of wood, bending strength, Young's modulus of elasticity, wood density Modifi kace představují procesy, které se používají ke zlepšení materiálových vlastností dřeva. Posledních 50 let je ve znamení velkého rozvoje studia cíle-ných změn vlastností dřeva. Spolu s rozvojem vědy a techniky dochází k tlaku na změnu již známých technologických postupů a vývoj nových postupů tvořících materiály se změněnými vlastnostmi.Plastifi kace neboli dočasná změna vlastností dřeva umožňuje jeho následné zpracování. Plastifikací se dřevo stává plastičtější a v důsledku uvolnění mezibuněčných vazeb je tento druh úpravy dřeva