Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2009
Abstract
Information given in EN 350-2 on natural durability of different wood species against wood destroying fungi is mainly based on heartwood tested in ground contact. The objective of this study was to test and compare durability of many different wood species in a field test in ground contact. The material consisted of Norwegian wood species able to give sufficient sawn wood dimensions (commercial and less utilised species, indigenous and introduced species) and imported species (Larch from Russia; Oak, Douglas fir and Western Red Cedar from North America; Merbau and Teak from Asia). Additionally, modified wood (thermally modified and tall oil treated) and preservative treated wood (CCA- and Cu-preservative) were included in the test. The wood types, 31 in total, were tested according to EN 252 and EN 350-1 at NTIs test site in Sørkedalen, Norway. Results after five years exposure show that most of the Norwegian grown wood species have low durability. This study also provides information on durability of four species not included in EN 350-2: Juniperus communis, Salix caprea, Sorbus aucuparia and Populus tremula.
Abstract
A range of studies the last decade have shown that modified wood can provide excellent protection against a range of wood deteriorating organisms, including decay fungi. However, we still lack information about why the modified wood is protected from microbial attack. Several hypotheses have been put forward e.g. inhibition of action of specific enzymes, but they still need testing. An understanding of the mechanisms utilized by decay fungi when exposed to modified wood is important for further optimisation of new modified wood products. In this study gene expression of the brown rot fungus Postia placenta has been monitored after 2, 4 and 8 weeks of colonization in furfurylated Scots pine and control samples. Preliminary results are given. The main finding was that genes related to oxidative metabolic activity was higher in furfurylated wood compared to untreated Scots pine, and that carbohydrate metabolism related expression was lower in furfurylated wood compared to untreated control.
Abstract
Mechanical strength properties are the most important feature of wood in constructions. In decaying wood strength loss can precede mass loss. Hence, both in laboratory and outdoor applications non-destructive measurement methods for early decay detection are in demand. The aim of this study was to evaluate the applicability of ultrasonic pulse propagation as a tool for decay detection in different laboratory setups. A dynamic MOE (MOEdyn) strength test device based on measurement of ultrasonic pulse propagation was used for non-destructive strength evaluation in different exposure situations for Scots pine sapwood. Two different test setups were used. In the first test MOEdyn was measured above fibre saturation. A range of different wood protection treatments were tested according to the terrestrial microcosms (TMC) test, a modified ENV 807. Three different soil types were used: forest soil dominated by white rot, Simlångsdalen test field soil dominated by brown rot and compost soil characterised by a mixture of bacteria and soft rot. Before strength testing the samples were water saturated and MOEdyn was measured above the fibre saturation point at time intervals (0, 8, 16, 24, 32 and 40 weeks) using ultrasound. Comparisons of strength loss were performed between treatments in the different soil types, and strength loss was also compared with mass loss. In the second test MOEdyn were measured below fibre saturation. Ultrasound measurements were performed on 0.5 m pine logs sampled from five trees from the same stand in central Southern Norway. Logs from two of the trees had varying amounts of discoloration due to an incipient attack by the white rot fungus Phlebiopsis gigantea during storage. Amount of visible discoloration had effect on MOEdyn values from measurements on log ends. Transversal measurement of MOEdyn was not successful. In a subsequent water uptake test, logs with discoloration absorbed substantially more water than the rest of the sample. The conclusion of this study was that the use of ultrasonic MOE is applicable as an evaluation tool in early decay detection.
Abstract
Wood is a traditional building material but in general it underlies restrictions in outdoor applications due to its respective durability against microbiological decay. To face this problem, different impregnation systems are applied to enhance the materials\" servicelife. Scots pine (Pinus sylvestris) is the most widely distributed pine in Eurasia and hence easily available. Despite of the previously defined good treatability of Scots pine sapwood, large differences in treatment performance are reported from industry. As process parameters are always adjusted to the material most difficult to treat, permeability variations in wood material are an economical problem. Therefore, it is important to understand the material in order to make a more reasonable material selection possible.....
Abstract
No abstract has been registered
Abstract
There is a need to establish new objective and sensitive methods for early detection and quantification of decay fungi in wood materials. Molecular methods have proven to be a useful tool within wood protection issues, however, this field is still poorly explored and so far relatively few have used these methods within the field of wood deterioration. Among the techniques used in the indirect quantification of fungi in decayed wood and building material are chitin and ergosterol assays. DNA-based methods are rarely used for identification in connection with quantification. Access to knowledge about fungal colonisation paterns in different wood substrates would allow further improvement of new products. The aim of this study was to investigate the colonisation pattern of decay fungi in wood samples after six years in soil exposure, in an EN252 test.....
Authors
Rastislav Solár Miroslav Mamo Janka Dibdiakova Jarmila GeffertováAbstract
A series of comparable specimens of spruce wood were submitted to chemical pre-treatments. Chemical pre-treatments were carried out with diluted sodium hydroxide, or sodium hydroxide and then by hydrogen peroxide, or per-acetic acid. All pre-treatments modified the chemical composition of wood and led to its weight loss. The pre-treatments resulted in a complete deacetylation, and partial delignification of wood and did not cause apparent loss of cellulose. Chemical alterations of the pre-treated spruce wood were markedly reflected in its improved digestibility under conditions of kraft cook. The obtained pulps were characterized with apparently reduced content of residual lignin, lower yield, moderate drop in DP, higher brightness and better optical properties (colour and lightness) of both unbleached and bleached pulps.
2008
Abstract
Norway spruce (Picea abies) is widely used not only in Norway but in many other European countries. Due to its refractory behavior after drying it is difficult to impregnate with wood protecting agents that makes it suitable for outside applications. In this research spruce wood samples are exposed to microwave radiation in order to improve the impregnability. The strength properties are evaluated after both microwave and impregnation treatment. The results show, that microwave treatment on spruce wood samples improves the uptake of impregnation agents. With increasing energy absorption due to microwave radiation the impregnability is improved. No differences could be found between the microwave treatments in radial or tangential direction, neither in uptake of wood preservative nor in strength properties. The uptake of impregnation agents in spruce wood is increased by using a pre-treatment with microwave radiation. However, some microwave treatments lead to cracks and a reduction in tangential strength. Most of the values of the process parameters used were obviously too high, which resulted in a distinct crack development.
Abstract
New restrictions draw governments, industry and research towards new and environmental benign wood protective agents. These agents often come from a natural source, and are also a waste product. One of these is chitosan. Chitosan is a derivative from chitin, mainly found in the exoskeleton of crustacean. Some research has been conducted on chitosan and wood. Chitosan has earlier proven good antifungal effectiveness, but to achieve a good protection, a 5 % concentration is needed, which makes the end product quite expensive. In recent research, a way to make chitosan treated wood hydrophobic has been invented. The objective of the research presented in this paper, is to describe the effectiveness of the following compounds: Chitosan, chitosan/copper, chitosan/boron and chitosan/Scanimp (a commercial wood preservative). Results show that chitosan works well alone, but has a fixation problem. Chitosan and boron give good fixation, and reduced amounts of chitosan and together give good protection against wood destroying fungi. The fire protection agents are promising, but needs higher concentration and/or better fixation to give a sufficient protection against wood destroying fungi
Authors
Erik LarnøyAbstract
To evaluate the decay resistance of wood, treated or untreated, for hazard classes 3, 4 and 5, the mass loss due to fungal exposure needs to be calculated. The standards for calculating mass loss in wooden test samples (i.e EN 113 and ENV 807) require that the samples used in the test are pre-dried to 0 % moisture content, m0, for determination of the initial dry mass. The standards describe that the samples should be dried at 103±2°C for 18 hours. When drying wood samples to 103 °C the samples are altered. Literature describes that extractives are influenced at temperatures as low as 60 °C, and redistribution and/or evaporation of these, will change the characteristics of the wood samples...