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
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...
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
The variations on the ratio of filling (RoF) were investigated on Norwegian grown Scots pine (Pinus sylvestris). The samples were taken from 10 different stands in south-east Norway, and treated with furfuryl alcohol and a copper-containing wood preservative. Both within tree variations, between tree variations and variations between stands were investigated for significant differences. Factors like horizontal and vertical positioning of the stem, annual ring width, density, tree height, tree age and latitude were tested. Samples of 20 x 20 x 60 mm were impregnated with a mild treatment scheme to avoid full penetration, which made it possible to distinguish the RoF. A significant variation was found between copper impregnated a furfuryl treated samples, favouring the copper impregnated samples. Within tree variations show a positive significance of the first log compared to the other logs, and a higher RoF in younger sapwood. The latitude of the stand gave a strong correlation, favouring southern stands.
Abstract
An easier penetrability and a more even uptake of wood protection agents is aimed for the two most common wood species in Europe, namely Norway spruce (Picea abies) and Scots pine heartwood (Pinus sylvestris), particularly when there is a great difference in absorption behavior of sapwood and heartwood. Microwave conditioning can improve permeability, reduce density and heat conductivity and change dimensional stability of wood. It could also improve the permeability of refractory wood species. This study deals with the evaluation of different parameters of a microwave treatment and their influence on the penetrability of water during dipping and impregnation of Scots pine heartwood and Norway spruce. Microwave irradiation lead to an increased water uptake after a submersion test, and after vacuum and pressure impregnation of the tested samples. This effect was more pronounced for Scots pine heartwood samples than for spruce wood samples. A short process with high microwave energy is recommended in order to reduce the development of large cracks but to increase the sorption behavior due to small checks in wood.
Abstract
Wood is a unique building material, but is by nature designed to deteriorate. A detailed understanding of the factors and interactions involved are important when working with service life prediction of wooden components in buildings. Wood may experience exponential fungal degradation caused by variation in the climatic factors within a small limited area and by minor imperfection in the wooden component. In this paper we put forward a new term: critical in-situ conditions (CIC). This is meant to bring the attention to the importance of looking into details in the construction design, the specific climatic factors and interactions involved. Gaining realistic and useful data for prediction of service life is only possible by controlling and understanding the factors that are target specific for a wooden component or even only a part of it. Performing measurements in a right way and in the proper part of the wooden component are vital for getting useful data for further processing. The objective in this paper is to exemplify the CIC in inservice situations and to describe the factors and interactions that control the service life. Case studies were performed on a building at Bryggen in Bergen, on a hunting cabin on Svalbard, on several wooden windows in the southern part of Norway and on an external wall of a residence house in Ås.