Durable and Modified Wood
Create the best bond
Whether outdoor furniture, patio decking or facades and bridges: The fields of application are constantly increasing for the modified wood species which have been highly demanded for several years. The great challenges in manufacturing are met with special adhesives.
Specialists for the bonding of treated wood
Wood species which are naturally less durable undergo a chemical or thermal modification procedure to increase the moisture and heat resistance and to make the wood suitable for outdoor use. After a thermal treatment during which the wood is heated to a defined temperature and then cooled down, the water absorption speed of the wood is reduced significantly. This process changes the appearance of the wood, making it darker. Alternatively, the wood may be impregnated and given water-repellent properties through a chemical modification process.
However, modified wood with a higher resistance to weathering is also more difficult to bond. Adhesives used for bonding these materials face a great challenge and have to be significantly more powerful than products used for bonding untreated wood. The substantially reduced moisture absorption and release as well as the added ingredients have a huge impact on the bonding properties of the substrate. This may lead for instance to chemical interactions with the added chemicals, which can have a detrimental effect on the bonding result. In addition, the use of water-based adhesives is usually also uneconomical. Due to the hydrophobic treatment of the wood, the water becomes trapped in the glueline and dries slowly leading to much longer pressing times.
For bonding modified wood, we provide special, chemically crosslinking adhesives which optimally meet the superior requirements. EPI (Emulsion Polymer Isocyanate) adhesives which are processed as two-component systems and mixed with isocyanate crosslinkers, ensure a fast setting of the adhesive even on durable wood with reduced water absorption. In addition, the chemical reaction of the crosslinking agent leads to a bond with high heat resistance. Therefore, EPI adhesives are optimally suitable for gluing hardwood, wood with a high resin content, and tropical wood species even with direct exposure to weathering. On the other hand, the setting time of one-component PUR prepolymers is not affected by the reduced water absorption of the wood due to 100% solid content. Both adhesive systems enable bonds with a moisture resistance considerably superior to the requirements for the durability class D4 of the EN 204 and reach tensile shear resistances > 7 N/mm² at 80 °C in heat resistance tests according to EN 14257.