Bonding with Loctite

Loctite adhesives have been used in manufacturing for decades, but the rapid change in the way materials are used mean the German firm that owns Loctite is on a never-ending quest to ensure manufacturers have a range of adhesive products that are effective and environmentally safe.

Nick Peters visited Henkel AG’s main adhesives R&D and Loctite production plant near Dublin.

The classic Loctite application – securing vibration-prone threads.
The classic Loctite application – securing vibration-prone threads.

It’s never a great idea to demonstrate research results to a journalist in the lab, the consequences of failure being all too obvious.

But that’s what Henkel research chemists Aine Mooney and Ray Tully did for me – nervous grins on their faces – as they applied squirts of Loctite HY4070 adhesive onto two smooth steel plates, then clamped them together.

We waited a few minutes while the glue cured, chatting about the dangers of getting too attached to their work (glue puns are rather too easy to come by, I’m afraid) and then, the moment of truth.

Each plate had been attached to a rope, so Aine and Ray took an end each and started to pull, hard. I gritted my teeth, but it was OK. The glue held like a charm. Smiling with relief, we all acknowledged this was strong stuff. Except, of course, it had stood up to a much stronger test than this.

Going loco

The adhesive used in the lab tug-of-war was Loctite HY4070, a hybrid that combines cyanoacrylate (CA, what consumers know as Superglue) with methacrylate (MA). The fast-curing qualities of CA meld with the flexibility and staying power of MA to provide a best-of-both solution, strong enough to pull, well, a train.

It was in Düsseldorf last year that the Loctite locomotive, dressed in a very fetching red livery with the logo across its nose, was hooked up to a 208-ton freight train via two steel plates, onto which was applied a scant three grams of Loctite HY4070.

This article first appeared in the June issue of The Manufacturer magazine. To subscribe, please click here.

Just 15 minutes were allowed for the cure, and then, nerves a-jangle, the order was given for the locomotive to advance – in front of 200 VIP guests from manufacturing and retail.

Advance it happily did, the adhesive providing sufficient grip to drag 208 tons of railway wagons behind it, a load that must have been magnified by the considerable friction and inertia that had to be overcome.

“Imagine if this didn’t work,” Dr Kourash Bahrami, corporate VP of Henkel Adhesive Technologies said on the day of the trial. “It would be a disaster, right?”

Perhaps, but it is hard to imagine that they hadn’t trialled this dozens of times before exposing it to so many outsiders. When it comes to a product that, for instance, keeps most of the world’s cars on the road in one piece, nothing is left to chance.

Since then, the Loctite loco has starred in this industrial version of the man-pulls-bus- by-his-teeth show all over the world, and you can see the feat in action in the video below:

Stuck, in the past

The journey to this ‘Loctite moment’, as it has been dubbed, started in 1953 in a research laboratory at Trinity College in Hartford, Connecticut. Dr Vernon Krieble, an entrepreneurial professor there, discovered how to make an anaerobic sealant using methacrylate.

‘Anaerobic’ means the substance will harden in the absence of air. This sparked a massive demand from engineers across the globe, who had since the dawn of the age of nuts and bolts endured endless issues with nuts that worked loose under pressure or vibration, or even just time.

Apply a few drops of Krieble’s Loctite threadlocker to the bolt, then, when the nut hits the liquid, air is driven out and the liquid hardens, forming a seal strong enough to keep the join tight. The savings in maintenance time were huge, thanks to a few drops of Krieble’s wondrous invention.

Engineers from car mechanics through to advanced manufacturing engineers are likely to have a tube or bottle of Loctite threadlocker to hand.
Engineers from car mechanics through to advanced manufacturing engineers are likely to
have a tube or bottle of Loctite threadlocker to hand.

To this day, engineers from car mechanics through to advanced manufacturing engineers are likely to have a tube or bottle of Loctite threadlocker to hand.

(If you have ever indignantly questioned why your new bottle of Loctite is less than full, then it’s anaerobic nature is the answer – it needs that air at the top of the bottle to keep it in its uncured liquid state.)

It was in the 60s that Krieble made the next major leap forward that was to change the world of adhesives forever. He licenced a product that had been developed in 1942 by the Eastman corporation – cyanoacrylate – and began to market it as as Superglue.

‘Make it by the ton, sell it by the drop!’ became the mantra. Therefore, the triumph of that locomotive pull is directly down to him: Loctite HY4070 uses both of these key ingredients.

In 1997, the German company Henkel, which numbered among its wide portfolio of holdings many different types of adhesive (including the Pritt Stick), bought Loctite, to create the Henkel Adhesive Technologies unit.

It then set about turning the company’s Dublin facilities into the centre of advanced adhesive R&D, creating many more variations to meet the continuing demands of industry for adhesives that will work under all conditions.

The development of hybrid adhesives, mixing cyanoacrylate with either methacrylate or epoxy, was a direct response to the challenge of bonding different substrates, such as metal to plastic, with joints that are not completely flush, as Patricia Cullen, AG Henkel’s director of global product development told me.

“Our products have to be a lot more robust and a better able to deal with a higher level of variability than we saw in the past, and they need to be able to bond metal and plastics, at gap, very robustly and consistently.

“We found many new applications in the automotive sector and in general industry for hybrids in terms of being able to bond different substrates and parts that don’t fit perfectly. If you have a gap, or you have parts that don’t fit well together, hybrid adhesive is the best solution.”

A degree of flexibility is important too. As anyone who has used consumer Superglue to mend breaks will confirm, the result can be quite brittle and if dropped, can break. Certain Hybrid adhesives absorb shocks and vibration so that seals and joins in manufactured goods can easily withstand daily knocks and jolts.

Sustainable bond

Not just glue – Henkel’s deep knowledge of applying thin layers of materials to substrate surfaces means they also supply gasket products, such as oil-resistant Loctite 518.
Not just glue – Henkel’s deep knowledge of applying thin layers of materials to substrate surfaces means they also supply gasket products, such as oil-resistant Loctite 518.

Patricia Cullen oversees an R&D operation that would be the envy of many. At least 45% of the people working at Henkel R&D in Dublin are science PhDs, such is the attraction of working on these vital products that hold our world together.

And it is not just the demands of manufacturers for ever-more effective ways of bonding materials that researchers like Aine Mooney and Ray Tully need to satisfy. They face environmental demands too, as does any manufacturer using chemicals, to remain compliant with changes to environmental legislation.

“More and more we find our end users come to us with a black list of chemicals,” Patricia told me. “We will work with them to take those particular chemicals out of our products, because sustainability is very important.

“Plus, of course, we have people making our products in our production line, so we have to protect them as well as making sure, as a company, that our solutions are compliant.”

Patricia added that there is a hidden sustainability dividend in using adhesives because every joint that is bonded with one of their products doesn’t have to be welded or brazed, obviating the obvious environmental impact of those two processes.

A 3D future

Where next? Not surprisingly, given the considerable overlaps, the Henkel Adhesive Technologies unit is getting very involved in 3D printing. It already provides extremely precise drop-by-drop delivery systems to customers, a process that is not a million miles from 3D printing.

Therefore, the company is working with two partners, developing new delivery systems with Carbon and new 3D materials with HP.

With Carbon, Henkel is working on specialised dispensing equipment for polymerisation-based 3D printing technologies. Between them, they have developed a meter mix and dispense device (MMD), a resin dispensing system and an accessory to Carbon’s SpeedCell manufacturing system that allows for proper dispensing of Carbon’s materials in bulk quantities.

Loctite adhesives are used throughout manufacturing industry wherever parts need to be reliably secured.
Loctite adhesives are used throughout manufacturing industry wherever parts need to be reliably secured.

With HP, Henkel is working on materials for their powder fusion-based Jet Fusion technology. In addition, the company has become the first global reseller of HP Jet Fusion 3D Printing solutions to enable qualifications among industrial production.

Henkel is a choice partner for these 3D printing stars because of the width and depth of its global supply chain, which Patricia Cullen says gives them all a tremendous opportunity.

“We have a very diverse range of customers across the world,” she said. “It started off, I suppose, when Loctite was a drop-by-drop product, and we had small users of our products, so we work closely with distributors, but, we also have a lot of feet on the street as well.

“We have a lot of our sales people who are out there in ‘golden sales’, as we call them, which are the sales units positioned all over the world who visit the large OEM customers.”

A new building has been added to Henkel’s Tallaght campus just outside Dublin, and when opened later this summer will act as a demonstration-cum-learning centre for the advancement of 3D printing technologies.

The buzz of excitement was palpable when I visited during its early stage development, demonstrating the deep commitment of the company’s long-standing and unusually loyal workforce to the quest for ever-more efficient adhesives and associated applications.

It’s as if they are imbued to this day with the spirit of the American genius who started it all 65 years ago.