Green gluing of two tropical timbers part ii: mechanical performance of resorcinol-phenol-formol (rpf) and one component polyurethane (1c-pu) adhesives using ayous (triplochyton scleroxylon) and frake (terminalia superba) substrates

Green gluing of ayous (triplochiton scleroxylon) and frake (terminalia superba) from Cameroon was investigated. Two room temperature curing glues namely resorcinol-phenol-formaldehyde (RPF) and one component polyurethane (1C-PU) were used. Each wood species was conditioned at various moisture contents and their influence on bond linesshear strength assessed. Block shear specimens for RPF were tested dry (in tropical conditions). Wood glued with 1C-PU was tested dry, cold soaked and vacuum- pressure treated. Delamination rates were measured.Results showed a high wood failure rate and a good ultimate shear strength with RPF when the wood moisture content (MC) is below the saturation point (13- 25% MC). The shear strength of both samples decreased with increasing moisture content. A trend of good compatibility of the two woods (single and mixed) is observed with 1C-PU for high moisture content. Slightly delamination of 2.4% was observed (minimum requirement 10%) and all species specimens developed high shear strength with high wood failure percentage.The 1C-PU appeared to be the most qualified adhesive for tropical green wood.