In this work, the suitability of nanofibrillated cellulose (NFC) as a novel component for wood coatings has been evaluated. NFC was prepared from two different wood pulps with a high pressure homogeniser and a grinder, depending on the initial fibre size of the two pulps. The fibrillation process was monitored using viscosity measurements and scanning electron microscopy. Viscosity measurements were found to be a suitable, reliable and especially fast and easy method for process monitoring, optimization and quality assessment of the NFC fibrillation process. NFC was mixed with four different waterborne acrylic polymer emulsions and analysed regarding its rheological behaviour. The viscosity of the acrylate-NFC suspensions was dominated by the NFC, whereas the polymer type was of minor importance at the tested concentrations. The viscosity increased exponentially after NFC addition and consequently the viscosity of such suspensions would be precisely adjustable in the considered shear range. During accelerated storage at elevated temperatures, the general flow behaviour did not change; only a slight viscosity increase was observed. The study shows that rheology is an important issue that has to be taken into account when applying NFC as additive in water based coating systems and that NFC is suitable as component for coating applications.
Inventory, emission factors, and total yearly emissions of
creosote, PAH, and phenols from the Swiss railway network
were determined based on the analysis of cross sections
of selected railroad ties which were in use for up to 46
years. Approximately 9 million wooden railroad ties
are installed in Switzerland, each being treated with
roughly 15 kg of creosote. During the service time of a
typical railroad tie of 20−30 years, about 5 kg of creosote
are emitted, corresponding to an emission factor of 208 mg/(m2 × day). PAH emissions occur as emissions of the volatile
2- and 3-ring PAH (such as naphthalene, acenaphthylene,
acenaphthene, anthracene, fluorene, phenanthrene;
boiling point up to 340 °C). PAH emissions for an average
railroad tie were found to be about 0.5 kg (sum of 16 EPA-PAH), corresponding to an emission factor of 20.3 mg/(m2 ×
day). Emissions of phenolic compounds were determined
to be in the range of 10 g for each tie, corresponding to an
emission factor of 0.58 mg/(m2 × day). According to our
study, about 1710 t of creosote components are being emitted
by the ties of the Swiss railway network, every year.
Based on the values reported above, yearly emissions of
2- and 3-ring EPA-PAH add up to 139 t. Cumulated emissions
of phenolic compounds are in the order of 4 t per year.
Wood, a natural and abundant source of organic polymers, has been used as a scaffold to develop novel wood-polymer hybrid materials. Through a two-step surface-initiated Atom Transfer Radical Polymerization (ATRP), the porous wood structure can be effectively modified with polymer chains of various nature. In the present study, polystyrene and poly(N-isopropylacrylamide) were used. As shown with various characterization techniques including confocal Raman microscopy, FTIR, and SEM/EDX, the native wood ultrastructure and features are retained and the polymer chains can be introduced deep within the wood, i.e. inside the wood cell walls. The physical properties of the new materials have been studied, and results indicate that the insertion of polymer chains inside the wood cell wall alters the intrinsic properties of wood to yield a hybrid composite material with new functionalities. This approach to the functionalization of wood could lead to the fabrication of a new class of interesting functional materials and promote innovative utilizations of the renewable resource wood.
-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
Composite films of nanofibrillated cellulose (NFC), derived from beech wood pulp, and 8 commercial acrylic and alkyd polymeric binders were prepared. Structural and mechanical properties of the composites were assessed by microscopy and tensile tests before and after aging. While the NFC was compatible with acrylate polymers, it formed undesired aggregates during processing with the alkyd polymers. Modulus of elasticity, tensile strength, and elongation at break of prepared films depended on the initial properties of the neat polymers. All composite films were stiffer, stronger, and less extensible than the corresponding neat polymer films. The reinforcing effect increased with increasing NFC content. Aging by artificial weathering strongly affected the mechanical properties of neat polymer and composite films. Alkyd films became, compared to the acrylate films, much stiffer and more brittle after artificial weathering. The results of the mechanical tests are regarded as promising step to use NFC as novel component in wood coatings.
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