It’s often the case that the simplest solutions can be overlooked when trying to solve a problem. Sometimes the answer is so obvious it’s staring you in the face. According to Bob Goss, senior technology specialist at Henkel, that solution can often be glue.
Goss has worked with adhesives for more than 30 years, researching and developing different formulas and applications to help clients in almost every sector throughout the country find the right adhesive for their needs. Attaching two components together is one of the most basic operations in manufacturing. To Goss, adhesives are often overlooked as a joining solution to the detriment of a product or machine.
“Our biggest competition is tradition,” he says. “There’s still people out there that don’t believe in adhesives. Awareness is low of modern adhesives and the many possible applications they are suitable for among engineers.
“Adhesives aren’t taught in universities, in mechanical engineering courses, as a production solution.”
The Henkel site in Hemel Hempstead, Hertfordshire was the UK production plant for Loctite adhesives. German company Henkel acquired the site and the Loctite brand 15 years ago and it is now an R&D and customer service centre. Henkel has 170 manufacturing and 17 R&D sites in 120 countries around the world. It owns consumer brands such as Persil and Schwarzkopf hair spray as well as industrial adhesive brands such as Loctite and Technomelt. Henkel has a long history in adhesives – it started out 90 years ago producing ‘hot melts’ for cardboard boxes.
Colin Chapman, marketing manager at Henkel, says: “We supply solutions. People don’t use adhesives because they want to. They are using them because they provide a simple and cost-effective solution compared to other methods.”
Free of fixings
The firm works in sectors including transport, primarily supplying coatings for cars and aircraft. Adhesives are used throughout modern vehicles, from the fixing of interiors to things such as flanges in gearboxes. “For example, without adhesives you wouldn’t have loudspeakers like you do today, which have no mechanical fixings, no bolts,” says Chapman.
Around 16% of Henkel’s adhesive sales are in what the company terms ‘general industry’, eve-rything from syringes to coffee tables. The company provides solder and adhesives for electron-ics and also supplies to builders, consumers and craftsmen. This is part of the adhesives story – glue is in fact used everywhere, and, without it, many things we use every day would simply become unstuck. “There’s even adhesives in car engines,” says Goss.
There are several different types of adhesives, including butyls, silicones and epoxies. Each has its own characteristics and qualities that make it more or less suitable for different applica-tions. Recently, R&D at Henkel has focused on ‘hybrid adhesives’ that marry two different types together to produce an adhesive with the most desirable qualities for certain applications.
Technology specialist Goss says that different adhesives are suitable for different applications and materials. Recommending the best adhesive for an application, by far the most common request from customers, is therefore difficult. “There are so many different applications, you can’t say for this you need to use Loctite A, B or C,” he says. The key consideration, he adds, is the type of stress in the joint – whether it is a tensile, shear, compressive, peel or cleave load.
Dispensing made easy
Another important aspect of adhesives technology is how it is dispensed in a manufacturing process. At Henkel in Hemel Hempstead there is a small team of engineers and technicians dedicated to developing bespoke adhesive dispensing systems, from small table-top ones to large boiler-sized machines, “up to basic robotic systems,” says Goss.
If the company is not able to supply a complete equipment solution, Henkel will work with ma-chine tool and equipment makers and just handle the dispensing end. The use of adhesives can often provide a simpler, more efficient and effective manufacturing solution, he says. “A robot may not be able to screw bolts into a flange or gasket, but it can often easily apply a ring of adhesive.”
The firm’s engineers work closely with a wide variety of engineering and manufacturing com-panies. Henkel is involved in the development of Dyson’s next generation of motor to power its range of hand and hair dryers and vacuum cleaners. “You wouldn’t be able to have those mo-tors without adhesives,” says Goss.
Henkel also develops and supplies bespoke adhesives, which could include, for example, prod-ucts with special UV curing properties for electronics manufacturers. “We aim to get people on the standard grades, but there is a team of chemists who modify the standard products. It’s a process that can take from three months to three years,” says Goss.
“We aim for a close relationship with our customers, to help them improve their processes and products with new technology, so we are often out on site visits,” adds Chapman.
Company-wide, areas of innovation in adhesives naturally focus on materials science and chemistry. Recent developments include magnesium coatings, which protect from friction and wear. ‘Teroson’ sound-deadening materials have been developed as an adhesive, and are also available as foam and matting to fill hollow spaces in vehicles and buildings.
Researchers are looking into improving the health and safety aspects of many adhesives – re-ducing odour and using less ‘risky’ chemicals in their formulation. Engineers are also working on the inclusion of adhesives in 3D printers, to give the parts produced added strength. And the joining of metals, such as aluminium and steel, is an active area of research. Goss says: “Inno-vation can come from customer-driven applications, where they are looking for a particular product. It also comes internally, from our chemists and engineers.”
Lasting bonds
Engineers in manufacturing will often opt for fastening or welding because they are tried-and-trusted methods that likely don’t require any additional training or process changes. But adhesives can provide tough, durable bonds to a wide variety of surfaces. They can improve assembly strength, design flexibility, corrosion protection, and can save you money.
There are pockets of engineering expertise all over the UK and it’s easy to overlook them. One such place is the Henkel adhesives centre. Stick around for a while and you might learn a thing or two about adhesives that proves useful in a future project.
Stick with it: Know your adhesives
Cyanoacrylates: These instant adhesives are characterised by their very rapid curing at room temperature, and are ideally suited for bonding small parts and where one of the materials in the joint is an engineering plastic or rubber. Cyanoacrylates will also bond metals, wood, leather and fabrics. The moisture on the surfaces neutralises the stabiliser to initiate the cure.
Anaerobics: These adhesives are widely known as thread-lockers but they are also used for thread sealing and for high-strength bonding of co-axial metal-to-metal machined joints. They are also used for flange sealing. The adhesive cures owing to the presence of metal and the absence of air. The parts can be handled in 10-30 minutes, but will take 24 hours to reach full strength.
Epoxies: These adhesives are used for structural bonding and require a resin and a hardener. A wide range of epoxies are available, including electrically and thermally conductive grades. Their toughness, durability and chemical resistance mean they are used in a variety of applications, from small devices to wind-turbine blades and Formula One cars.
Methyl methacrylates (MMAs): Often used for plastics and glass but also for many other substrates, MMA adhesives are typically less sensitive to variations in mix ratio and variations in the degree of mixing. The cure profile of MMA adhesives can be adjusted more readily than with other types of two-component adhesives. Most MMA adhesives are formulated with modifiers to provide tough bond lines that resist peel and cleavage stresses as well as impact.
UV reactive acrylic adhesives: Used especially in the medical industry and for optical components for bonding clear plastics and glass. A UV lamp of the correct wavelength and intensity is required. The major benefits of these adhesives are the rapid cure, optical clarity, and the ‘cure-on-demand,’ as they will not cure until exposed to ultraviolet light.
Hot melts: Used in the packaging industry and in products such as shoes but also used for overmoulding, which uses elements of casting and injection moulding technologies to encapsulate and protect components such as PCBs and connectors.
Polyurethanes: Very adaptable products used for vehicle windscreen bonding, caravan construction, and composite bonding, among many other structural applications.