Performance of one-component polyurethane (1C-PUR) adhesives in the production of finger-joints fabricated from four planted forest species

The adhesives used in the production of engineered wood products mainly influence the mechanical performance of structural elements. In this context, the present paper aims to evaluate the bonding performance of two different one-component polyurethane adhesives (1C-PUR-A and 1C-PUR-B) in the production of finger-joints made from four planted forest species (Tectona grandis, Eucalyptus grandis, Eucalyptus urograndis and Pinus spp.). Tensile tests were performed to evaluate the strength and failure modes of seven combinations of structural adhesives and wood species from planted forests in Brazil. The finger-joints made from hardwood species (T. grandis Group 1: 35.1 MPa, E. grandis: Group 2: 45.5 MPa; Group 3: 55.8 MPa, E. urograndis: Group 4: 37.9 MPa; Group 5: 43.0 MPa) presented greater mean value of tensile strength than those made from softwood species (Pinus spp.: Group 6: 21.9 MPa; Group 7: 24 MPa). Therefore, the feasibility of using these hardwood species in the production of engineered wood products becomes evident. Moreover, the tensile strength of finger-joints with one-component polyurethane depends on the wood species utilized in the production. One-component polyurethane presented good adhesion in finger-joints made from T. grandis and Pinus spp. given that 90% and 80% of failure mode did not occur on the bondline respectively. On the other hand, the failure mode of finger-joints made from Eucalyptus spp. occurred mainly on the bondline of one-component polyurethane adhesives.