Adhesive joint formation between porous wood adherends with one-component polyurethane part 1

Modern timber engineering is based on homogenised, strength-graded timber elements, mainly bonded with different types of adhesives. The actual development and increasing meaning of the wood construction would not have been possible without the adhesive technology. The following paper presents some of the results of a comprehensive study of the impact of a number of selected process parameters on the formation, quality and performance of glue lines. To ensure consistent production quality, the bonding geometry (glue line thickness) should be kept constant. The tested adhesive joint quality based on tensile shear tests according to EN 302–1, supported by microscopic analyses, shows that the pressing pressure leads to the overpressing of unevenness, compaction of the adhesive and suppression of blistering in one-component polyurethane adhesives. The penetration depth of the adhesive is not affected by the variation of the pressure. Delamination tests according to EN 302–2 to assess durability in combination with the prevailing pressure distribution show no obvious correlation. However, it does provide an indication that the surface preparation and treatment exert a crucial influence on the bond geometry and therefore on durability.