droxide and nitric acid. The wafers were stored for several days under these conditions and the changes were observed by measuring the water contact angle in air using a Gonionometer from Dataphysics (OCA 15+).

The Modulus of Elasticity (MOE) and the hardness of fibril reinforced hydroxypropyl cellulose films were determined by nanoindentation. In addition, the fibril alignment in the composites was analysed by Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The results show that the formation of fibril networks is of great importance for the mechanical properties of the nanocomposites.

-European beech (Fagus sylvatica L.) is a popular and major tree species in Europe. The economic value of its timber is greatly decreased by the red heart phenomenon. The cause of red heart formation is well understood. However, scientific investigations about the technological and mechanical behaviour of red heartwood are scarce. Our study aims to provide a sound scientific basis for the characterization of technological properties, adhesion-as well as colour-behaviour of red-hearted beech. The mechanical and technological properties of redhearted beech give no evidence of different behaviour in comparison with the normal beech wood. The adhesion behaviour shows equal results. In terms of colour stability, the difference between freshly processed normal and red beech wood diminishes after certain time of exposure. red heart / adhesion behaviour / colour stability / mechanical technological property / Fagus sylvatica Résumé -Le bois de hêtre (Fagus sylvatica L.) -Propriétés technologiques, comportement au collage et stabilité de la teinte du bois de coeur rouge. Le hêtre (Fagus sylvatica L.) est une espèce d'arbre populaire important en Europe. La présence du coeur rouge provoque une réduction notable de la valeur économique des grumes qui en sont atteintes. Les causes de l'apparition du coeur rouge sont bien connues mais les études scientifiques sur le comportement technologique et mécanique du hêtre à coeur rouge sont cependant rares. La présente étude a pour but d'établir des bases solides pour la caractérisation des propriétés technologiques du hêtre à coeur rouge que sont le comportement au collage et la stabilité de teinte. Il n'existe aucun indice selon lequel les propriétés technologiques et mécaniques du hêtre à coeur rouge diffèrent de celle du hêtre normal. Pour ce qui est du comportement au collage, les résultats sont identiques alors que pour la stabilité de la teinte la différence à l'état frais de sciage entre le hêtre normal et le hêtre à coeur rouge diminue après un certain temps d'exposition. coeur rouge / comportement au collage / stabilité de teinte / propriété technologique et mécanique / Fagus sylvatica

Determination of the fracture toughness of MDF hoardFracture toughness is a measure for the crack resistance of a material. This paper presents the results of an analysis on the infuence of density and moisture content on fracture toughness of MDF. Fracture toughness was measured using ASTM E 399 with CT-specimens (parallel to the board direction). Acoustic emission analysis and scanning electron microscopy (SEM) were used to assess the kind of fracture and the fracture surface. Higher fracture toughness values were found with increasing density. An increase in moisture content caused a decrease in fracture toughness. Acoustic emission analysis showed no clear results regarding the kind of fracture of MDF. According to SEM fibres were nearly torn out of the MDF board. Fractures of fibres, as they occur in particleboard, were not observed.

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