Strength of Adhesive Joints of Thermally Modified Ash Wood Glued With Polyvinyl Acetate-Based Adhesives

Adhesives for gluing thermally modified wood were analyzed.The methods for conducting experimental studies to determine the strength of adhesive joints of thermally modified ash wood and unmodified pine wood, using polyvinyl acetate (PVAc)-based adhesives of durability class D4 were described.According to the results of experimental studies based on the proposed methodology, it was established that the strength of adhesive joints of thermally modified ash wood and unmodified pine wood stretched along the fibers after the first stage of testing is 6.21 MPa, after the second stage 4.56 MPa, and after the third stage 3.90 MPa.The average strength of the adhesive joints of the control specimens is 7.12 MPa.According to the obtained research results, the nature of destruction of the adhesive joints of thermally modified ash wood and unmodified pine wood was determined depending on the test stage.The greatest destruction occurred on the adhesive line, and the least on the pine wood.It was assumed theoretically that during the thermal modification of ash wood, hemicellulose decomposes and acetic acid is released, leading to the formation of furfural, which impairs wood surface wetting and affects the adhesive strength of PVA-based adhesive joints.