VOLUME 49, ISSUE 5/2008

Besides the traditional wet log storage methods several examinations have dealt with the working out of alternative storage methods recently, for example log storage under foil. The feasibility of the practical introduction of this method can be established with suitable economic calculations. The article is about the results of the comparative study of economic efficiency for the different methods of traditional log storage and that of under foil. The accounts are based on the comparison of the approximate investment expenses and the discounted operating expenses, suitable for the inflation, of the particular methods, with regard to the storage capacity of 500 m 3. The results show that the investment expenses of log storage under foil arealot lower (55 to 60 %) than those of the traditional wet storage. The operational expenses of the new method are also more favourable, but the difference is not that striking. On the basis of the results, storage under foil should be advised mostly in the case of new plants, due to the favourable investment expenses.

Laboratory trials have shown that the use of Substitute D instead of the so far conventionally industry-wide used accelerator (lithium carbonate) leads to a significant reduction of the pressing time of cement-bonded particleboards. Thus it is possible to increase the production capacity or to improve panel properties and achieve savings in energy with constant production volume, respectively. Since Substitute D shows good solubility, when compared to the hard to dissolve lithium carbonate, the property values are more evenly distributed (lower standard deviation) among other things. Apart from internal bond strength, which is tolerably decreased, the use of longer particles results in an improvement of the mechanical properties of cement-bonded particleboards. As a consequence it is possible to decrease the mean board density or the panel thickness, respectively. When using longer particles the proportion of cement can be increased, which results in savings in material costs

Over the last years there was an increase in interest of using WPC for constructive application, mainly related due the possibility of producing composites with tailor-made strength and stiffness. One of the main drawbacks of WPC is the relatively low impact strength, which excludes these materials from several applications. In this work two possible ways of impact modification are discussed for dissipating the impact energy throughout the composite (matrix modification and increasing the aspect ratio of the reinforcing material) for increasing the impact strength of the composites. The composites were produced via extrusion and injection moulding, respectively, with different amounts of modifiers, and were characterised via mechanical testing. It was shown that it was possible to increase the impact strength through the use of polyethylene as an additive as well as with the use of small amounts of natural fibres. With these results it should be possible to find new perspectives for structural application with these materials.

Beneath measuring techniques photographs are used to document the rating of machined wooden surfaces. This report shows, how the quality of these photographs can be improved by the use of tilt objectives, dark field illumination and 3D-macroscopic photographic methods.

It has successfully been proven for the first time that the modification of PF resins with protein containing components, which are by-products in wheat preparation, enable the manufacture of virtually formaldehyde-free wood-based panels with high moisture resistance. Upon condensing 10 to 30 % of this natural component, phenol-resin content could be equally substituted. This means that such a bonding system contains fewer synthetic components, which, in the long run, also contributes to preserving the limited fossil oil and gas resources. Phenol resins that are established and are available on today’s market make the manufacture of extremely low-formaldehyde wood based materials possible, which also, without any restrictions, meet the Japanese requirements of F**** quality. By applying the developed resin system, the formaldehyde content of the manufactured particleboards, OSB and MDF could additionally be reduced to about a tenth [1, 2, 3] when compared to traditional phenol systems. Both laboratory and industrial testing revealed that the addition of proteins did not result in obvious deterioration of any mechanical or hygric parameters

Choice of adhesive raw material is determined by the requirements of the adhesives user. Many requirements of modern adhesives can still be fulfilled through the use of traditional raw materials, such as those from renewable raw materials that are based on plant and animal resources: In 2006, nearly 15.5 % of all adhesives used were based on renewable raw materials. In addition to their use as basis materials, renewable raw materials are often used as additives or as monomers for polymerization in adhesives that are based on synthetic raw materials, because of specific benefits that they impart. However, some special requirements of modern adhesives cannot be fulfilled by traditional renewable raw materials, and it is necessary to modify these plant- and animal-based

substances to achieve desired specific properties in the formulated adhesive. Modified renewable materials are an interesting raw materials source for adhesives.

The correlations for the formaldehyde testing of OSB were determined using the common European test standards with the chamber method EN 717-1 as reference and the perforator test EN 120 and the gas analysis test EN 717-2 as derived methods. The determinations were done with nine OSB of industrial origin and six OSB produced in the technical lab of WKI. Additionally, the values from previous tests of 18 industrial OSB could be included into the statistical evaluation. The obtained results confirmed the suitability of perforator and gas analysis methods for product und production control over the full range of the emission class E1. Basing on the correlations, E1 threshold values for OSB formaldehyde testing can be calculated.

The detection of cracks and poorly glued wood bondings is an important but up to now not sufficiently solved task for the industry. Using high power ultrasound to activate vibrations within the solid wood leads toafast heating of the surface along the tiny cracks, around black knots and within poorly glued bondings. The increasing temperature can be detected by using thermography and the defect part can be repaired or separated from the process. First laboratory experiments show the capability of this technique on solid wood, OSB and particleboards.

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.