12/03/2014

www.gupta-verlag.de/polyurethanes

GL-certified adhesives technology for rotor blade production

[image_0]With a new adhesive technology for the production of rotor blades, Henkel has made its entry into the wind power market. The portfolio of adhesives engineered under the Loctite brand is based on polyurethane technology. According to the manufacturer, the new adhesives come with a variety of benefits: They can reduce the energy required for bonding rotor blades, shorten the production time and thus reduce overall costs. In addition, as a result of their ability to fully cure at room temperature, they combine utmost process reliability with automation potential, particularly in bonding applications involving small components or poorly accessible joints.[image_1_right] Although new to wind turbines, polyurethane adhesives have long been demonstrating their remarkable performance potential in other industrial sectors, says Henkel. In shipyards, for example, they have been exhibiting resistance to temperatures as low as -180 °C in marine applications for about 40 years. In refrigerated superstructures on truck semitrailers they provide additional structural strength. And the solvent-free polyurethane adhesives are also used to manufacture mobile homes and snowboards. Henkel says it has invested around four years of research in this technology which is totally new to the wind power sector. The outcome so far is five Loctite-brand adhesives, all of which have been tested by Germanischer Lloyd under various criteria and are now certified.[image_2] A decisive advantage of polyurethane adhesives for production processes is the reduced exothermy of their reaction, and hence low shrinkage, compared to the established epoxy resin technology, says Henkel. Although polyurethane adhesives are capable of curing without any additional energy, the process is usually accelerated by applying external energy. While epoxy resin adhesives need a relatively high heat input, polyurethane adhesives cure at a lower heat, thus substantially reducing energy needs and taking less time. The speed of curing and thus of production can be varied via the amount of heat introduced. As a rule of thumb, an increase of 10 °C in temperature cuts the curing time by half. This rapid, catalysis-controlled setting behaviour is now being exploited in repair and component bonding. In addition, the setting behaviour of Loctite products can be flexibly adjusted, and polyurethane bonds can be relied on to fully cure, says the company. The comparatively low curing temperatures and the low exothermic reaction temperature are kind to the bonded materials. For example, rotor blade half-shells bonded with polyurethane adhesives show less stress cracking in the course of time. The adhesives' elasticity also has an appreciable supportive effect. Polyurethane technology also exhibits superior fatigue and ageing behaviour, according to Henkel.

www.gupta-verlag.de/polyurethanes