VOLUME 49, ISSUE 6/2008

Many forest companies aim at converting poorly structured forest into nature-oriented forests, because of rising social and economic demands, as well as to encounter the anticipated climate change. Beech (Fagus sylvatica) is being considered because it is the potential natural vegetation. Silvicultural strategies building up mixed cultures – including selected neophytes species – are expected to provide an economic base for forest companies. Because of its high yield, favourable wood properties and compatible ecological attributes, increasing cultivation of the North American grand fir (Abies grandis) has been suggested. The development of new production processes for wood products from these novel species is crucial regarding the utilization of beech and grand fir wood. In the following articles the utilization of grand fir solid wood are being introduced, as well as innovative proc

The research paper introduced here is intended to promote information about sawn timber characteristics of the Abies grandis and to gather data with regard to possible uses of the sawn timber. This will make it possible to establish future uses of the sawn timber and to ascertain to what degree the broad spectrum of sawn timber can be complemented with this fast growing variety. Using approximately 1 000 samples visual sorting according to DIN 4074 [5–8] was done. A comparison with results obtained by sorting with the aid of the “Timber Grader” manufactured by Brookhuis Micro Electronics and then performing a destructive bending test according to DIN 408 [4] showed that the visual sorting greatly underestimated the load capacity potential of the wood. In addition to examining important technological characteristics the research continues for uses for which the typical characteristics of this light wood are advantage and which lead to its independent uses.

The production of OSB does not exclusively depend on fresh cut round wood. As an example of low value beech and grand fir it is well documented that maxi chips as well are appropriate for the production of high value planar strands. The portion of big planar strands will considerably rise if the maxi chips are pre-treated thermo-hydrolytically before chipping in a knife ring flaker. The gross density of the wood is an important influence factor regarding the mechanical properties of the OSB. Consequently the grand fir is a more preferable OSB raw material to beech.

Wood of beech (Fagus sylvatica L.) and grand fir (Abies grandis (Douglas ex D. Don) Lindl.) was used for production of sandwich boards with beech particles in the intermediate layer and grand fir particles in the overlay. Changes of wood properties due to the production process were detectable by FTIR-ATR spectroscopy. In particular, an influence of the additives, such as urea-formaldehyde resin and paraffin were identified. Using principal component analysis and cluster analysis for spectral evaluation, significant differences between the samples were found, which could be related to the particular production step. The results document that FTIR-ATR spectroscopy combined with multivariate statistical methods has the potential to determine product composition and is suitable for quality control.

The aim of these investigations was to develop new processes for the production of high valuable sandwich boards. Basically the suitability of beech timber and grand fir timber should be ascertained for the production of particleboards. Thereby grand fir and beech have been combined in such a way that harmful beech swarf could be avoided. The method of resolution was a spatial separation of the timbers in middle layer and surface layer. Thereby beech particles were only used in the middle layer. These novel boards already achieve the European standards at low densities. Regarding to the mechanical-technological properties sandwich boards were superior to the reference boards made of industrial particle compositions.

By molecular DNA methods, 24 different fungal species, mostly ascomycetes and related mitosporic fungi, were identified on dead wood collected from the station of the forestry office Ahlhorn. Two isolates were white-rotting basidiomycetes. Baiting fungi by wood bars in soil contact revealed sensitivity towards brown rots. Decay tests after EN 113 confirmed a high sensitivity of Abies grandis towards brown rot and a certain degree of resistance towards white rot and especially against soft rot.

The detection and reconstruction of fungal damages on wood in buildings require increasingly a precise identification of the fungi. In particular this applies to the doubtless determination of the dry rot fungus Serpula lacrymans, which is the most frequent and at the same time the most dangerous wood destroyer in buildings in Central Europe. In the last years molecular-biological methods are used increasingly for the diagnostics of wood destroying basidiomycetes. DNA analytics ensure an objective and safe identification. Their application is particularly meaningful in damaged wood without visible fungal mycelia or with insufficient fungal morphological characteristics. In the IHD routinely DNA analytic methods for the detection of S. lacrymans and other important fungi were developed by using the internal transcriped spacer regions ITS 1 and ITS 2 of the ribosomale DNA. The most quickly and most economical analysis method at present is the Species-specific Priming Polymerase chain reaction (SSPP). The security of the findings can be increased by additional employment of the Amplified Ribosomal DNA-Restriction Analysis of the ITS-Region (ARDRA-ITS). The identification by sequencing of the rDNA-ITS region with following alignment to primary genetic databases is the most universal method. Due to the high costs their employment for the routine diagnostics is currently not meaningful in the wood preservation field yet.

Particle board enjoys great importance within the industry of derived timber products and has evolved to become an extremely differentiated product since the 1950s. Meanwhile, the particle board market displays both a tendency to generalise, i.e. developing products for a variety of applications, and to specialise by developing niche products. This article draws on selected examples to demonstrate the interplay between the most important influential factors and the ensuing product extensions, and provides an outlook as regards the foreseeable developments in the near future.

The present article initially gives an overview on the emission categories and their historical and legal context from the first set of criteria in the late Seventies to the modern well toxicologically-risk assessed benchmarks of today. The second part describes the implementation of hot gel time test for reactivity measures of F4star resins. The latter part depicts the aging behaviour of F4star resins in respect to the reactivity. The properties of urea-melamine-formaldehyde resins for composite boards change with ongoing storage time. This effect is especially visible in reactivity of investigated products, which allow to reach F4star emission category. Due to reduced formaldehyde content the curing is slow, notably with Ammonia salts. This reduces obtainable press times in industrial production of composite boards compared to conventional E1 resins. Mostly the F4star products production parameters are at limits of resin reactivity. Just under these aspects the influence of storage time has to be regarded. It was shown, that storage has positive implications on the reactivity of low emission resins, which expects a higher performance of this resin system in production of composite boards.

The paper highlights the main events related to the formaldehyde release of wood-based panels over the last decades and updates on what has happened and what may happen in the near future. Thereafter, it discusses the formation of formaldehyde in the atmosphere. Formaldehyde can be formed by oxidation of hydrocarbons in the atmosphere; the decomposition of formaldehyde in the atmosphere can take different pathways including photochemical and chemical reactions. The emission of formaldehyde from wood-based panels has been reduced dramatically over the last years. This process has been promoted by the “Guide line for use of particle board with respect to the reduction of unacceptable formaldehyde concentration in the room air” (ETB-Richtlinie 1980/1981) and the DITB-Richtlinie 100 (1994). Nowadays, wood-based panels can be produced industrially with formaldehyde emission well below the limits prescribed by the DITB-Guideline (100) and matching more or less the formaldehyde release of wood itself. The paper dwells upon the formaldehyde release from wood itself and its dependence on different factors. Discussion on the health effects of formaldehyde emitted from wood-based panels of the E1-class and lower is expected to fade away as it seems to have no sound scientific background.

Due to a wide variety of design options and the high quality, powder coating is an attractive technology for wood based panels. UV-curing powders are particularly suitable, because the high speed curing process can be operated at a temperature of about 120 'C, having low impact on the heat sensitive panel substrate. For the rapid powder melting before UV-curing, gas-infrared transmitters are used. With the state-of-the-art powder coating techniques, productive processes with velocities up to 100 m/min, like in horizontal liquid painting lines for wood based panels, are not possible. A new gunless powder application technique now enables high speed powder coatings in compact horizontal lines.