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Assessing and optimizing strand geometry and orientation to produce strengthened OSB

: Fur, X. le; Thole, V.; Plinke, B.

Fraunhofer-Institut für Holzforschung, Wilhelm-Klauditz-Institut -WKI-, Braunschweig; European Panel Federation -EPF-:
5th European Wood-Based Panel Symposium 2006. Proceedings : 4 - 6 October 2006; Maritim Airport Hotel, Hanover/Germany
Braunschweig, 2006
European Wood-Based Panel Symposium <5, 2006, Hannover>
Conference Paper
Fraunhofer WKI ()

As its production increased tenfold in the last ten years in Europe, OSB represents today more than a simple alternative to plywood. While it could be now considered as a well-established wood-based panel, oriented strand boards do not yet achieve optimal properties. Proof of this are the technological developments being carried out intensively in RTD for every process step, from flaking until pressing. This paper deals in two first parts with possibilities of assessing crucial parameters such as strand size and orientation using innovative off-line and on-line methods. The latter are based on image processing and were developed at the Fraunhofer insitute, Wilhelm-Klauditz-Institute for Wood Research (WKI) for answering both industrial and laboratory needs in matter of optimization of structure.
Particular attention was paid to the statistical characterization of a batch of strands: It was shown that main dimensions of a population of strands are mostly lognormally distributed and then may be described using a small set of suitable indices. Numerous batches were analysed and the influence of climatic and processing parameters on post-disintegration was investigated. For industrial applications, an on-line mat quality assessment system ready for use between the forming station and the press was developed.
To illustrate possibilities of structure optimization, results of investigations of strengthening of OSB with strands of optimal geometry will be presented. Thanks to additions of small quantities of veneer strips, the so-called "uniform strands", the bending properties of panels were highly increased. Advantages could be taken of that statement by saving on adhesive amounts so as to reach properties required by norms, or by putting on the market a strengthened OSB. The surface evenness that affects the suitability of OSB regarding painting and coating was also assessed using a measuring technique based on fringe-projection and image processing. The quantitative analysis shows how uniform strands close pores on surface and make the product more appropriate to coating.