In rotor blade production, one obvious way of accelerating the process would be to use polyurethane-based adhesives for rotor blade bonding, although these represent a very recent development in the wind power industry. Traditionally, blade shells and spars have been bonded using two-component epoxy resins. While these materials reliably meet the extremely high mechanical specifications, they are rapidly reaching their limits when it comes to the automation of manufacturing processes. New technologies are therefore needed to speed up and automate production.
Henkel is now presenting a solution in the shape of its newly developed polyurethane adhesive Macroplast UK 1340. The specialist in high-performance polyurethane adhesives has succeeded in developing a PUR adhesive that satisfies the specific mechanical requirements for use in the wind power industry and, on top of this, makes rotor blade production more efficient.
Higher capacity utilization through faster curing
One of the major benefits offered by Macroplast UK 1340 is its accelerated cure speed. Polyurethane-based adhesives react much faster than the epoxy resins used up to now. Since it is not only highly reactive but also produces less reaction heat, this two-component adhesive considerably reduces both the duration and the temperature of the cure phase. Extensive tests have shown that substantial reductions can be achieved in bonding and tempering times. The lower cure temperature also has a positive impact on energy consumption in addition to reducing the risk of stress cracking due to excessive thermal loading. And heat-sensitive foam inserts also remain unaffected.
What is more, Macroplast UK 1340 satisfies the high mechanical demands for this application, as confirmed in a variety of tests. The key criterion for achieving the technology shift is described by Nicole Schlingloff, product developer at Henkel who played a major role in developing this product: “One absolute essential for wind energy plants is that they have to be in technically perfect condition. Rotor blades are among the most highly stressed components one can imagine. Even the tiniest flaws can have disastrous consequences, and that can result in high costs for repairs, downtime, or even replacement of complete rotor blades. For all of those reasons, we had to make sure that Macroplast UK 1340 would entirely satisfy the market’s high demands.”
GL approved and IWES tested
Macroplast UK 1340 fulfills all the key parameters specified by Germanischer Lloyd (GL) and is the first PUR adhesive in the world to have obtained GL approval. GL’s requirements for the adhesive primarily relate to its tensile shear strength, resistance to aging, creep behavior and glass transition. Rotor blades manufactured using Macroplast UK 1340 have already proven their worth in a field trial of more than twelve months.
Further evidence of the functional capabilities and fatigue strength of the processed adhesive was recently furnished when it successfully passed load tests performed by the Fraunhofer Institute for Wind Energy and Energy System Technology IWES. In a long-term test lasting some four months, an ENERCON rotor blade bonded with Macroplast UK 1340 was subjected in Bremerhaven to stresses and strains that would normally occur over a period of 20 years. The bonded joints of the 40-meter long blade passed the static and dynamic tests specified in the IEC 61400-23 standard to determine the rated load and fatigue behaviour of the blade. The test criteria specified for approval of wind energy plants were met without any problems. And ENERCON’s own specifications were also satisfied in this blade test.