Effects of strands geometry on the physical and mechanical properties of oriented strand boards (OSBs) made from black spruce and trembling aspen

INTRODUCTION

The Eastern Canadian softwood lumber industry is exploring alternative uses for softwoods’ primary processing residues considering the overcapacity of softwood chips traditionally produced for the pulp and paper industry. Trembling aspen is the more standard species used for oriented strand board (OSB) production in Canada. Therefore, the use of softwoods for OSB manufacturing, including black spruce, is not common in Canada. It is known that the physical and mechanical properties of OSB, a multi-layer structural board, mainly depend on the species, the strands geometry, the adhesive, the adhesive content, the hot-pressing time, the hot-pressing temperature, and the closing rate of the press (Winandy and Kamke 2003). The inner structure of this type of strand-based product is formed of many micropores and voids because of the complexity of the strand geometry and the randomness of the strand distribution within the panel (Zhang et al. 2005). The strand geometry is an essential factor that affects the panel structure. Therefore, it impacts the panel performance and manufacturing costs (Suchsland and Xu 1989; Marra 1992; Lenth and Kamke 1996; Geimer et al. 1999; Dai et al. 2007; Li et al. 2008, 2009).

As one of the main parameters for strands geometry, the strand length significantly impacts panel performance. Some researchers (Nishimura et al. 2001; Barnes 2001; Chirasatitsin et al. 2005; Beck et al. 2009; Iswanto et al. 2019) studied the influence of the strand length on the properties of OSB panels. These studies indicated that the strand length has a significant impact on the bending properties of OSB panels. However, the strand length has no significant effect on other properties, such as the internal bond (IB). Another report (Febrianto et al. 2012) analyzed the influence of the strand length on the properties of three-layer OSB and found that it affects the bending properties in the parallel and the perpendicular directions. In addition, the strand length did not influence the thickness swelling (TS). Oriented strand boards made from long strands have better parallel bending properties than those made from short strands because of their better alignment and greater overlap (Suzuki and Takeda 2000; Meyers 2001; Nishimura et al. 2004; Chen et al. 2008).

Brochmann et al. (2004) investigated the...