How to choose an adhesive20 October 2017

How to choose an adhesive How to choose an adhesive

There has been a surprising number of mishaps with glue over the years. People commonly mistake the adhesive for eye drops or lip balm, leading to trips to A&E. When choosing their adhesive, engineers don’t need to be quite as concerned as the general public, but should avoid making any costly mistakes to avoid bonded surfaces from failing.

The majority of industrial adhesive jobs can be covered by three main adhesive categories. Cyanoacrylate adhesives, commonly known as super glues, structural adhesives or acrylics and anaerobic adhesives are all used to bond surfaces, known as substrates, together. However, these adhesives all have different properties, meaning that engineers must be able to accurately differentiate between them.

“The main point for choosing an adhesive is to look at the substrates being joined,” Peter Crossen, VP of the maintenance and partsmaster innovation platform at NCH Europe, said. “Of course, the same adhesive will not always have the same effect when joining metals as it will when joining two pieces of wood.

“The way that the two substrates are joined and the stress on the joint also affects the adhesive that should be used. An angled join increases the bond area and strength between the two substrates, but a thin section of join can be prone to breaking, meaning a stronger adhesive should be used. If the join is also exposed to a lot of tensile or peel forces, a structural adhesive should be used to maintain the strength of the bond.

“NCH Europe has recently developed super structural technology (SST), which uses nanoparticles to strengthen the bond of metal, standard plastics and composites. Low NRG plastics are traditionally very difficult to bond, so engineers should look for adhesives that feature nanoparticles to help them to securely fix these pieces together.”

The required strength of the bond also impacts the choice of adhesive. Some users must regularly disassemble components as part of the maintenance schedule, meaning that they should choose a lower strength anaerobic adhesive to bond two substrates together.

However, if a low strength adhesive is used on other parts, this could lead to a serious structural failure for a piece of vital equipment as cyanoacrylate adhesives generally have poor peel and impact strength. In such cases, structural adhesives should be used, which have a high level of tensile and peel strength with an excellent resistance to impact.

“Cure time should also be considered when choosing an adhesive,” Crossen added. “If a quick fix is needed, a cyanoacrylate should be used, which takes seconds to cure. If more time is available, then a stronger bond can be achieved with structural adhesives, although they can take up to two hours to cure. In this case, users must decide whether the strength of the adhesive or the speed of the cure time is more important.”

When choosing an adhesive, how it will be applied is important. Some products require mixing a base and an activator however, this can lead to being improperly mixed and subsequently ineffective adhesives. By using a product that can dispense the two parts of the adhesive at the same time through a mixer nozzle, this can avoid any errors in the formulation. “By choosing the right adhesive, companies can also avoid buying large amounts of inventory,” Crossen continued. “Opting for adhesives that can be used on a wide variety of materials and surfaces, ensures that each adhesive is cost effective and is not only used occasionally on one material.

“Mistaking eye glue for eye drops is not an everyday occurrence, but careful consideration should be taken when deciding on what is the best adhesive to bond substrates. Getting it right can reduce time to maintain or, increase the life of item.”

Mark Venables

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NCH Europe Ltd

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