Bonding of wood-plastic composites (WPC)—material and surface modification for special applications

As part of the current research at the Kunststofftechnik Paderborn (KTP), foundational experiments are being conducted on adhesive bonding of wood-plastic composites (WPC) with dispersion adhesives. The setting mechanism of this type of adhesive is characterized by the evaporation of the dispersion medium (water). The challenge is therefore to remove the water in the adhesive fluid from the joining plane. In conventional applications, dispersion adhesives are used to bond wood, paper, or other porous materials. Wood-plastic composites, however, which consist of wood particles in a polymer matrix, cannot absorb the necessary amount of water within the required time period, as they do not possess a similarly porous structure. Part surfaces are treated in various processes in order to expose the wood fibers. This is intended to improve the material’s capacity to absorb water, which should lead to more rapid setting. In addition to surface treatments, the WPC formula is modified by the addition of hygroscopic additives. A further approach is to drill holes at regular intervals into the joining plane as additional points where evaporation can occur. The water in the adhesive layer migrates towards these holes through diffusion processes and then evaporates into the ambient atmosphere.