VOLUME 59, ISSUE 5/2018

Wood, which is a natural raw material, shows great variations in the material properties even within one type of wood. Different location conditions and growth areas are important impact factors. A total of 119 spruce trunks (Picea abies (L.) Karst.) from North Tyrol and South Tyrol harvested from north and south hillside orientations at various sea levels (MSL) (810 m to 2,060 m) were investigated in order to determine the influence of exposure and sea level on the material properties. The equilibrium moisture content, the density, the bending strength, the modulus of elasticity, the compressive strength, the Brinell hardness and the maximum linear swelling were determined form clear defect-free specimens.

Traditionally, tropical wood species are used in musical instruments. Tighter protections and the inclusion of typical woods for musical instruments in the Appendices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and related trade restrictions are leading to a greater debate about tropical wood use. Therefore, there is an increasing need for the musical instrument industry to deal with substitution possibilities of protected tropical woods. This article describes ways to substitute protected, tropical wood species in musical instruments, but also further research and development needs. In a joint effort of manufacturers and research institutes, the capacity for innovation can be strengthened and thus marketable and accepted solutions might be establish.

The prevention of illegal logging and wood trade requires reliable methods for the identification of species and geographic origin of wood and wood products. Conventional microscopic analysis of wood anatomical structures has its limits, especially with regard to wood origin. An alternative is DNA analysis. Thereby, one of the most critical issues is the availability of analysable DNA in lignified cells. To determine appropriate markers for DNA analysis, the DNA structure in wood and corresponding green material was investigated. For spruce, fir and oak, it has been shown that DNA of the nuclear and plastid genome, but not of the mitochondrial genome, is present in the wood. Analyses of the DNA content in stem and branch wood showed that DNA can be obtained in all areas of the stem cross-section as well as in different stem heights.

Fracture-mechanical approaches are increasingly used for the testing of adhesive bonds. It is assumed that there are always defects in a component. The conditions for development these cracks are determined. This includes the fracture toughness Kc in the three modes I, II and III or the fracture energy. In the present paper, characteristic values for beech wood bonded with 1C-PUR and with PRF with variable wood moisture content and load angle between mode I and mode II are determined. The assessed fracture energy of PRF is in the range of solid wood, while the 1C-PUR without primer application lays significantly below. For 1C-PUR without primers usually adhesion failure occurs. The fracture energy increases with the moisture content of the wood. The fracture toughness Kc shows a clear influence of the angle between mode I and mode II as well as the wood moisture – Kc decreases with the moisture content of the wood. The fracture toughness KIc of PRF is higher than that for 1C-PUR.

In Sweden and other Scandinavian countries, wood waste materials are normally used for biofuel production or waste incineration. From environmental perspective, it is favourable to recycle wood material and use the concept of multiple sequential use than just burning it for short-term energy production. One of the objectives of this study was to investigate the feasibility of manufacturing environmentally friendly variants of particleboards with low formaldehyde emissions based on combination of tannin-formaldehyde (TF) resin, PMDI and wood waste to clarify the effect of the re-placement of PMDI by TF resin, on the formaldehyde release compared to particleboard board from wood waste bonded by urea-formaldehyde (UF) resin. In this study untreated wood waste material (type AI) was used to produce three-layered particleboards bonded by a combination of tannin-formaldehyde resin and PMDI resin (TF-PMDI hybrid resin) and UF resin. The particleboards were produced with a target density of 640 kg/m³. For each panel variant the extractable formaldehyde content and formaldehyde release were analysed. The results point out that it is possible to manu-facture ultra-low formaldehyde emission three-layered particleboard variants based on recycled untreated wood waste material (AI) bonded by a combination of TF and PMDI hybrid resin with ratios of 30 % : 70 % and 40 % : 60 %, which demonstrated, that the replacement of PMDI by 40 % tannin resin is possible. The produced particleboard still comply with the European standard EN 312 (2010) as well as show superior properties in formaldehyde release (3 h and 24 h) and extractable formaldehyde content comparable with particleboard bonded by UF resin. Also a significant reduction of formaldehyde release after 24 h with 25 % is obtained by replacing PMDI with TF from not only 30 % but 40 %.

The second part of the publication is about the laboratory production and the material properties of cement-bonded plywood (CBPly). The laboratory production of the new material can be done with the basic process steps of the cement-bonded particleboard (CBPB) manufacture. Only the application of the binder on a large and plane face is a fundamental different process step in comparison to the production of cement-bonded particleboards. Most properties of the new material are a combination of those of organic-bonded plywood and cement-bonded particleboard. In difference to organic-bonded plywood it was possible to improve the behaviour of CBPly in terms of its fire behaviour and its formaldehyde emission. In contrast to cement-bonded particleboards the density of CBPly can be decreased tremendously which leads to a better process ability. Furthermore, especially the strength of cement-bonded plywood exceeds the mechanical values of cement-bonded particleboards. Solely the resistance to moisture did not show the expected behaviour, as derived by the known behaviour of CBPB. The new material class allows an intensified use of wood-based panels for constructions with high resistance to fire.

Flammable surfaces made of wood, such as floor and wall coverings, are only widely accepted as flame-retardant products. For appropriate product developments the cone calorimeter (ISO 5660-1, 2015) is an established laboratory fire testing device. For the necessary large-scale fire classifications, flame propagation along the surface (flame spread) is to be evaluated, which is not possible in the cone standard configuration. Therefore the qualification of a modified, so-called RIFT arrangement with flame spread burn in the cone calorimeter was investigated. An experimental program with products of several types of wood, thicknesses and surfaces was implemented in order to develop significant RIFT parameters for suitable fire classification prediction models. As a result, due to the substantive equivalence of the RIFT parameters, which were proven to be significant in the multiple linear regressions, and the corresponding classification parameters to be calculated, models with high predictive accuracy could be derived.