Effect of chemical and thermal modification, and material replacement on strand board properties

Abstract

The purpose of this paper was to analyze the effects of various OSB-strand modifications on physical and mechanical properties of strand board. Norway spruce (Picea abies L. Karst) strands were acetylated using acetic anhydride or thermally modified at 180 °C using atmospheric pressure and superheated steam environment. Strand boards made of acetylated strands (Acet), thermally modified strands (TM) and thermally modified strands used only at surface layers (TMSL) were produced. Furthermore, strand boards with 20% (Cork20%) and 40% (Cork40%) cork particles were manufactured. Wood-water relations, i.e., equilibrium moisture content (EMC), water absorption (WA), thickness swelling (TS), as well as mechanical properties, i.e., bending strength and internal bonding, were tested and compared to untreated reference strand board. The EMC for TMSL was no different than the reference boards, however, the other boards had a statistically significant decrease in EMC. Acetylated strand board and boards with cork particles had a significant increase in water resistance. The mechanical properties decreased for TM and Cork40%, but no difference was shown for Cork20%. Acetylation increased internal bond strength. The results provide a comparison between different modifications of strand boards and show a new possibility of reducing the water effects on OSB with cork particles.