Effects of gluing conditions for formaldehyde-free tannin adhesive on the oriented bamboo scrimber board properties

The formaldehyde-free tannin adhesive (AcBTanGlu) was synthesized by bark extractives of Acacia confusa and hexamethylenetetramine, and was further used for production of the oriented bamboo scrimber board (OBSB) in this study. When Acacia bark extract tannins are mixed with 2% hexamethylenetetramine, the OBSB pressed at a hot pressing temperature of 150 degrees C for 15 min can obtain the maximum mechanical strength. The tap tone velocity (V-t), ultrasonic-wave velocity (V-u), dynamic modulus of elasticity (DMOEu), dynamic modulus of tap tone velocity (DMOEt), screw holding strength (SHS), and dimensional stability of AcBTanGlu glued OBSB are significantly higher than those of UF and PF glued ones. AcBTanGlu glued OBSB also has higher modulus of elasticity (MOE)((//)) and modulus of rupture (MOR)((//)) values than the parallel structure laminated bamboo board (LBB) and laminated beams made with whole moso bamboo (Phyllostachys pubescens). The 12-week decay test with L. betulina and L. sulphureus showed no significant difference between OBSB glued by AcBTanGlu and UF (p > 0.05). The results of this study will help the bamboo processing industry to gain an understanding of the properties of AcBTanGlu glued OBSB.