## 1 Introduction  
Oriented strand board (OSB) are known as 'Sterling board' in the UK and 'Aspentie' in the US and Canada, and they represent tri-layered boards with high mechanical properties used for construction (shacks, temporary construction, sheepfold, false floors, etc.) and are made of long strands of about 80-120 mm. The starting point for their achievement was the wafer-board and flake-board, boards obtained from wide chips with large gluing surfaces, at which the length and orientation of the strands and tri-stratification was performed. The surface of these boards is rough, reason why it is used less often in furniture production. The superior properties and the low price of these boards make it possible to replace the plywood in constructions, even under conditions of high humidity (there are OSB boards for exterior and interior use, according to EN 300 [1]). The United Nations Economic Commission for Europe (UNECE) [2] showed that the level of plywood and OSB in 2015 was higher in North America than in Europe and CSI, but the production of OSB and MDF (medium-density fiberboard) was much higher in Europe than those two comparison regions (Figure 1). Also, if we compare the production capacities for the countries of Europe and Asia (United Nations Economic Commission for Europearea), it can see that on the top there are countries like Germany, Romania, and Russia, and countries like France and UK are only in positions 8 and 10, respectively (Figure 2). Some authors [5] studied the influence of the thickness of the strands on the properties of the OSB boards in the lab from cut veneers, finding that the properties of the boards with 0.38 mm thickness of strands were similar to those of the solid wood from which the veneers were cut. The authors did not take into account the fact that in industrial technology the strands are irregular at the ends and thickness, they are aciform, dimensionally varied, and very rough, characteristics that have a positive effect on compaction and densification, obtaining properties much better than in the case of strands obtained from veneers. Other authors [6] analysed the influence of 80 mm long strands of _Pimus taeda_ L. on the properties of tri-stratified OSB with the ratio of 1:2 on layers and the density of 0.75 g/cm\({}^{2}\). It was found that all mechanical properties exceed the requirements of the standards in the field. Another study [7] showed that the influence of the fineness of the strands observing that the resistance to internal bond (IB), the modulus of rupture (MOR), and the modulus of elasticity (MOE) increased to a level of fineness of 20%. It is also shown that the fine strands have a beneficial influence on the mechanical properties of the OSB boards by  
Figure 1: OSB production compared to plywood, particleboard, and MDF in UNECE region [3]. Figure 2: Top 10 countries referring to OSB capacities in UNECE zone [3; 4]. interposing them between the large strands, increasing the cohesion of the layers and compaction of the boards. In reference [8] the influence of three different strand lengths on the properties (MOR and MOE) of OSB boards was examined. The obtained results showed that the obtained properties met the minimum requirements of standard [1] and the length of the strand influenced these properties positively and significantly. Other authors [9] examined the influence of three strands lengths of 78, 105, and 142 mm and two thicknesses of 0.55 and 0.75 mm to observe the influence of strand geometry on the properties of OSB boards. Their conclusion is that a correlation must be made between the long length of the strand that offers good bending resistance and the small length of the strand that offers good compressive strength. The research [10] established that the heat treatment of OSB boards had a positive effect on thickness swelling and equilibrium moisture content (EMC).