Vienna, Austria
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Forsthuber B.,Holzforschung Austria | Schaller C.,BASF | Grull G.,Holzforschung Austria
Wood Science and Technology | Year: 2013

A study of the surface discolouration of clear coated wood during artificial and outdoor weathering and its prevention using clear coatings comprising organic UV absorbers (UVA) and mineral UV screeners was carried out. It was shown that the use of UVA and UV screeners in clear coatings was very effective in reducing photodegradation of the wood surface. Preliminary irradiation trials with Xenon arc light showed that the UV screener TiO 2 led to the least discolouration of the coated wood surface, closely followed by UVA of the hydroxyphenyl-s-triazine class (HPT). The artificial and outdoor weathering trials indicated that UVA of the HPT class stabilised the colour of the wood surface better than UVA of the 2-(2-hydroxyphenyl)- benzotriazole class (BTZ). Comparison of different artificial weathering methods indicated that Xenon arc light weathering showed the best match to the proceeding discolouration of the clear coated wood panels during outdoor weathering. © 2012 Springer-Verlag.


Forsthuber B.,Holzforschung Austria | Muller U.,Wood us Competence Center for Wood Composites and Wood Chemistry | Teischinger A.,University of Natural Resources and Life Sciences, Vienna | Grull G.,Holzforschung Austria
Polymer Degradation and Stability | Year: 2013

In this study, we hypothesized that the use of UV absorber of the hydroxy-benzotriazole class (BTZ) and micronized TiO2 (NTiO 2) as mineral UV screener could stabilize the chemical and mechanical properties of clear wood coatings based on a high Tg/low T g multiphase acrylic binder dispersion. The photooxidation rates were compared using ATR-FTIR techniques and tension tests. For qualitative and quantitative chemical analysis and correlation to the mechanical properties, multiple linear regression (MLR) was used, which was a suitable method to monitor the chemical changes of the polymeric binder and to investigate the influence of these light stabilizing additives on the photooxidation behavior. The analysis of mechanical properties of the acrylic binder during exposure to Xenon arc light showed that both BTZ and NTiO2 stabilized the Young's Modulus and the elongation at break during the whole cycle. BTZ showed better results. However, it led to a strong decrease of the initial Young's Modulus whereas NTiO2 showed no comparable effect. We concluded that BTZ was very efficient in reducing the photooxidation and the accompanied change of the elastic properties of the acrylic binder. NTiO2 only stabilized the high Tg component of the multiphase acrylic binder whereas the photooxidation of the low Tg component was accelerated. This may be explained by a photocatalytical activity of NTiO2. © 2013 Elsevier Ltd. All rights reserved.


Stefko J.,Technical University In Zvolen | Bednar J.,Holzforschung Austria
Key Engineering Materials | Year: 2016

The paper deals with laboratory air tightness testing of wood based construction materials with the focus on the proportion of air infiltration through the building envelope in the air exchange of the building. Results of the specific materials testing - cross laminated timber (CLT), OSB and other structural materials are analysed in the paper. Moreover, the effect of production technology, material, its thickness and surface treatment are studied. Results of laboratory testing provide valuable data for detailed computer modelling of air exchange through the infiltration, especially in vapour diffusion-open elements of building envelope. © 2016 Trans Tech Publications, Switzerland.


Denzler J.K.,Holzforschung Austria | Koppensteiner J.,Holzforschung Austria | Arthaber H.,Vienna University of Technology
International Wood Products Journal | Year: 2013

An important aspect in machine strength grading of timber is the direction of the grain and deviations from the main axis, which can cause a dramatic loss of strength. Therefore, an essential requirement of the wood industry is to find the direction of wood fibres in a fast and noninvasive way. For three decades now the use of polarised microwave radiation has been investigated, revealing the main direction of wood fibres in a non-contact and non-destructive way. The development of new small sized patch antennas now allows the detection of grain deviations on a local scale using a free microwave transmission method. This paper presents experimental results on accuracy and resolution for spruce specimens of different dimensions. Local signal variations, as well as boundary effects are discussed, particularly in view of possible industrial implementation. © 2013 IWSc, the Wood Technology Society of the Institute of Materials, Minerals and Mining.


Forsthuber B.,Holzforschung Austria | Muller U.,University of Natural Resources and Life Sciences, Vienna | Teischinger A.,University of Natural Resources and Life Sciences, Vienna | Grull G.,Holzforschung Austria
Polymer Degradation and Stability | Year: 2014

We investigate the influence of TiO2 in the anatase (ATiO 2) form on the chemical and mechanical properties of clear wood coatings based on a high Tg/low Tg multiphase acrylic binder dispersion. The photooxidation rates were compared using ATR-FTIR techniques and tension tests. The partial least square regression (PLS-R) used showed to be a suitable method to monitor the chemical changes of the polymeric binder and to investigate the influence of the photocatalyst on the photooxidation behaviour. The results obtained by comparing the relative photooxidation rates of the coating systems with and without ATiO2 showed that ATiO2 led to higher photooxidation rates, especially at the beginning of the exposure cycle. Tension tests proved that samples containing ATiO2 are characterized by a significant change of the elastic behaviour at the initial phase of the Xenon arc exposure. After 150 h of Xenon arc exposure, the change of the Young's modulus, which can be attributed mostly to the high Tg component of the multiphase binder, increased at a higher rate. We conclude that the photooxidation of the acrylic binder was strongly accelerated by ATiO2, whereas the effect of increasing concentration of ATiO2 is limited. © 2014 Elsevier Ltd. All rights reserved.


Dolezal F.,Holzforschung Austria | Spitzbart-Glasl C.,Holzforschung Austria
Energy Procedia | Year: 2015

Several initiatives have been launched to increase sustainability in building industry. All of them contain a shift in focus from energy consumption to a wide variety of indicators for the full life cycle. This implies a broader view, not only based on the ecological, but on the economic and social performance of buildings as well. A closer look on internationally acting Green Building Labels reveals that acoustic performance and noise protection is seen as an important part of the social sustainability aspects of a building. Thus, the approach of how to consider the acoustic performance and impact on rating results vary heavily. © 2015 The Authors.


Weidenhiller A.,Holzforschung Austria | Denzler J.K.,Holzforschung Austria
Computers and Electronics in Agriculture | Year: 2014

This paper deals with pattern recognition based on colour and texture. The aim is to detect areas of bark and wood on images of spruce logs taken in the industrial environment of a sawmill. Bark is a material with high natural variability in texture and colour even in a single tree species such as spruce and is a challenging subject for pattern recognition. The study compares three algorithms based on colour, texture and an integrated combination of colour and texture, respectively. Relevant sources of variation between and within logs are identified: colour variations on bark and wood, dirt, and traces of the bark beetle. Modifications of the algorithms with the potential to further improve the bark detection performance are discussed. © 2014 Elsevier B.V.


Sikkema R.,University Utrecht | Junginger M.,University Utrecht | Pichler W.,Holzforschung Austria | Hayes S.,National Energy Foundation NEF | Faaij A.P.C.,University Utrecht
Biofuels, Bioproducts and Biorefining | Year: 2010

The European wood pellet market is booming: concerns about climate change and renewable energy targets are predominant drivers. The aim of this analysis is to compare typical wood pellet chains from the purchase of the feedstock from sawmills to the conversion into heat or electricity. Cost structures, primary energy inputs and avoided greenhouse gas (GHG) emissions are reviewed. Three cases are defined: pellets for district heating (DH) in Sweden (replacing heavy fuel oil); bagged pellets for residential heating in Italy (natural gas); and Canadian pellets for electricity production in the Netherlands (coal). Supply may cost €110-€170 per tonne of delivered pellets, with the main cost factors being feedstock collection, drying and long-distance ocean transportation (for Canadian pellets only). Largest avoided emissions are for power production (1937 kg CO2eq/tonne of pellets), followed by district heating (1483 kg). In relative terms, the GHG reduction varies from 81% for residential heating (with pre-dried feedstock) to 97% for DH. Based on a wood-pellet consumption of 8.2 million tonnes, the EU27 plus Norway and Switzerland avoided about 12.6 million tonnes of CO2 emissions in 2008. Concluding, wood pellets can achieve substantial GHG savings, especially when substituting coal for power production. However, wood pellets are relatively expensive, especially compared to coal. Only in the case of high oil prices, can the substitution of heating oil for DH be commercially viable. In most other cases, substitution is only possible with financial support from national governments, for example, feed-in tariffs or carbon taxes. The commercial markets for CO2 emission rights may cover some costs, but their impact is still limited. © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd.


Denzler J.K.,Holzforschung Austria | Weidenhiller A.,Holzforschung Austria | Golser M.,Holzforschung Austria
Scandinavian Journal of Forest Research | Year: 2015

This paper summarises the comparison between log properties and resulting structural timber properties. The establishment of these relationships is a first step to place the grading as early as possible in the production process, if possible directly on the log. To find out what should be detected on the log, the modulus of elasticity (MOE) based on longitudinal frequency, the number of resin pockets and the value for spiral grain were detected. Relationships are established to the corresponding properties on the structural timber produced out of it and to visual log grades commonly used in Austria. This paper discusses advantages and disadvantages of these properties on 85 spruce logs. The MOE based on longitudinal frequency showed high potential whereas the number of resin pockets and the value of spiral grain only helped to identify timber unsuitable for construction. © 2015 Taylor & Francis.


Forsthuber B.,Holzforschung Austria | Grull G.,Holzforschung Austria
Polymer Degradation and Stability | Year: 2010

A study of the photocatalytic degradation of an acrylic dispersion based coating and its prevention using hindered amine light stabilizers (HALS) was carried out on solid films by exposing them to Xenon arc light. The degradation rates were compared using FTIR-ATR techniques by plotting the differential build up of the hydroxyl and hydroperoxide bands as function of exposure time. UV-Vis spectroscopic studies were carried out as well to obtain data about the light stabilization of organic UV Absorbers (UVA) and inorganic UV screeners by HALS. The effectiveness of an aqueous primer comprising a specific lignin stabilizing HALS in combination with clear topcoats with UVA or UV screeners in the prevention of photo-induced discolouration of wooden surfaces was investigated by measuring the colour change during exposure time. It was shown, that the usage of HALS was effective in reducing the degradation speed of clear coats with UVA and UV screeners. Results obtained by UV-Vis spectroscopic analysis during the exposure cycle showed an inhibition of the photo-degradation of the UVA themselves, while no positive effect occurred on inorganic UV screeners. A lignin stabilizer containing aqueous primer with a specific HALS as active component, showed some promising results in combination with transparent topcoats comprising organic UVA and inorganic UV screeners, except ZnO, where a strong antagonistic effect occurred. © 2010 Elsevier Ltd. All rights reserved.

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