Adhesion Matters

From Rivets to Glue: How Adhesives Built Modern Trains

• Season 1 • Episode 28

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All aboard for a journey behind the scenes of modern rail engineering! In this enlightening episode of Adhesion Matters, we explore how adhesives have evolved from background players to central pillars in rail car design and construction.

What You’ll Discover:

  • A Revolution in the Rail Yard
    From a mere ~10 kg of adhesive per rail car in the 1980s to as much as 500 kg today—adhesives have surged in importance, helping phase out rivets, welds, and bolts.
  • Bonding vs. Fastening
    Adhesives offer smoother, lighter, and stronger construction by bonding large panels directly, enabling design flexibility, structural integrity, and sleek aesthetics.
  • Quiet, Durable, Weatherproof
    Advanced bonding solutions enable superior NVH (noise, vibration, harshness) damping, corrosion resistance, and thermal sealing—critical for high-performance passenger comfort and longevity.
  • Specialized Chemistry in Motion
    From fast-curing methacrylate structural adhesives and rock-solid epoxies to flexible polyurethane and MS sealants, modern rail systems deploy precise chemistries tailored for specific use cases—like direct glazing high-speed train windows that withstand extreme pressure and vibration.
  • Behind the Bond
    Industry leaders—Dow, DuPont, Henkel, Huntsman—drive innovation. Together with specialized technical distributors (think mobile labs with DIN 6701 and EN 455-452 certification), they ensure safety (fire, smoke, toxicity), performance, and installation expertise.
  • The Future of Rail Adhesion
    Innovation continues through development of dual-cure adhesives (think UV rapid set plus chemical cure), bio-based chemistry, and even debond-on-demand systems designed to advance recyclability—a critical challenge in reaching transport sustainability.

Why It Matters:

Next time you're on a train—whether gliding silently through countryside or ferrying goods across continents—remember that advanced adhesives are holding more than you think together. This episode shines a spotlight on the unsung high-tech materials shaping the future of rail travel.

Elena Bondwell:

You're stepping onto a sleek, modern train, maybe a high-speed bullet train zipping through the countryside, or perhaps a massive freight car hauling tons of goods. What do you imagine is holding it all together? You know, heavy-duty rivets, strong welds. Well, today we're taking a deep dive into the truly unsung hero of modern rail, adhesives and sealants. And believe me, it's not just about a bit of sticky stuff. It's about a revolutionary shift in how train are designed and actually built.

Lucas Adheron:

That's absolutely right. Our sources today are quite a fascinating mix. We've got historical accounts, in-depth industry analyses, and technical reports from some of the leading chemical companies.

Elena Bondwell:

So quite a range then.

Lucas Adheron:

Definitely. And we're going to uncover what we used to just call glue as utterly transformed rail car construction. We're talking about making trains lighter, stronger, quieter, and incredibly safe. Our mission here really is to show you just how indispensable these advanced bonding solutions have become and what a critical role they play.

Elena Bondwell:

Okay, let's unpack this then. Prepare to be surprised, I think, by the sheer ingenuity behind something as seemingly simple as a bond. So when we think of early trains, our minds probably go straight to massive steel structures, right? Joined by countless rivets.

Lucas Adheron:

Yeah, and for the most part, that image is pretty accurate.

Elena Bondwell:

But you're saying even way back, 19th, early 20th centuries, adhesives had a role. A small one, maybe.

Lucas Adheron:

Exactly. A small but significant role. Primarily, they relied on traditional animal glues.

Elena Bondwell:

Animal glues.

Lucas Adheron:

Okay. Yeah. But these had severe limitations. They were really only suitable for interior applications, bonding things like wood or canvas components.

Elena Bondwell:

Because they couldn't channel the elements.

Lucas Adheron:

Precisely. They would simply soften or dissolve exposed to heat or moisture. But what's fascinating here is that window glazing was an early exception.

Elena Bondwell:

Windows? How so?

Lucas Adheron:

Well, old steam era rail cars actually used these putty-like sealants to bed the glass into frames. So window sealing was genuinely one of the very first adhesive applications in rail cars.

Elena Bondwell:

Huh. So these early glues were pretty fragile then. What was the turning point? What allowed adhesives to move beyond just like interior decoration?

Lucas Adheron:

Well, a major breakthrough arrived in 1911. There was a report of a waterproof glue.

Elena Bondwell:

Okay, waterproof. That sounds promising. A synthetic marvel.

Lucas Adheron:

Not quite, actually. It was still an animal glue, but mixed with formaldehyde.

Elena Bondwell:

Formaldehyde. Interesting.

Lucas Adheron:

Yeah. And crucially, it could be applied cold, and most importantly, it could withstand wet conditions.

Elena Bondwell:

Ah, that's the key.

Lucas Adheron:

That innovation meant adhesives could finally be considered for exterior parts or parts exposed to the weather It really paved the way for much broader adoption in train manufacturing later on. A subtle shift, but it opened up enormous possibilities.

Elena Bondwell:

Right. So fast forward to today, and we're obviously not talking about a few pounds of animal glue anymore. Not

Lucas Adheron:

even close.

Elena Bondwell:

And this is where the story gets, well, really compelling. The amount of adhesive in modern rail cars has absolutely skyrocketed. Just how dramatic is this increase we're talking about?

Lucas Adheron:

It's quite remarkable, really. An average rail car built back in the 1980s contained only about 22 pounds Maybe 10 kilograms of adhesive.

Elena Bondwell:

Okay, 22 pounds.

Lucas Adheron:

In stark contrast, some state-of-the-art rail cars today use up to 1,100 pounds. That's 500 kilograms of adhesives in their construction.

Elena Bondwell:

500 kilos? That's a 50-fold increase.

Lucas Adheron:

A 50-fold increase in just a few decades. And this isn't just a simple material substitution. This represents adhesives replacing hundreds, maybe even thousands, of rivets, bolts, and welds.

Elena Bondwell:

That's an astonishingly So why? What makes adhesives so much more appealing than those traditional mechanical fasteners? What's justifying this massive shift?

Lucas Adheron:

Well, it comes down to a really compelling array of benefits. They fundamentally reshape how trains are designed and how they perform.

Elena Bondwell:

Okay, like what?

Lucas Adheron:

First off, light weighting and energy efficiency. Adhesives let manufacturers use lighter materials like composites.

Elena Bondwell:

Ah, composites instead of just steel?

Lucas Adheron:

Exactly. And that directly translates to significant weight reduction. For instance, there are European regional trains, the AD Trans ones, that use large fiberglass sandwich panels. These are bonded with polyurethane adhesive instead of being welded.

Elena Bondwell:

And the result?

Lucas Adheron:

A lighter, stiffer car body. For you, the passenger, this means better fuel efficiency for diesel trains, better energy efficiency for electric ones, which reduces operational costs, and importantly, CO2 emissions.

Elena Bondwell:

Makes sense. Less weight, less energy needed. What else?

Lucas Adheron:

Then there's noise, vibration, and harshness reduction NVH.

Elena Bondwell:

Right, making the ride smoother.

Lucas Adheron:

Much smoother. NVH isn't just some technical term. It's really what differentiates a relaxing journey from a jarring, tiring one. Traditional fasteners, like rivets and bolts, they transmit every bump.

Elena Bondwell:

Turning the train into a big drum, basically.

Lucas Adheron:

Pretty much, yeah. But flexible industrial adhesives, like those from the leading brands, they act like tiny shock absorbers. They absorb vibrations, minimize acoustic intrusion. It just creates a much quieter, more comfortable environment inside.

Elena Bondwell:

I can appreciate that. What about strength? Are they really as strong as welds or rivets?

Lucas Adheron:

That's a great question. It's about enhanced structural integrity and durability. See, instead of concentrating stress at individual points like a rivet does, adhesives provide a continuous bond line.

Elena Bondwell:

Spreading the load out.

Lucas Adheron:

Exactly. Distributing stress evenly across the entire joint area. This leads to significantly enhanced overall structural strength and longevity. Think of it this way. An adhesive sealant might replace dozens of rivets when securing a floor panel to the chassis.

Elena Bondwell:

Okay.

Lucas Adheron:

It spreads the load uniformly across the whole surface, not just at those specific points. It makes the entire structure much more robust.

Elena Bondwell:

Interesting. What else is driving this?

Lucas Adheron:

Well, there's aesthetics and design flexibility. Adhesives create clean, weld-free joints. That dramatically improves the visual appearance, both outside and inside the train.

Elena Bondwell:

Sleeker look.

Lucas Adheron:

Yeah. And beyond just looks, they make it easier to bond to similar materials like metal to composite or metal to plastic. Things that are difficult or impossible to weld.

Elena Bondwell:

Opening up design possibilities.

Lucas Adheron:

Totally. It gives engineers entirely new options. And then there's cost-effectiveness.

Elena Bondwell:

Really? I'd assume high-tech glues are expensive.

Lucas Adheron:

The materials themselves are specialized, yes. But adhesives can lead to some Okay, that makes sense from

Elena Bondwell:

a manufacturing perspective.

Lucas Adheron:

And there's corrosion, prevention, and sealing. Adhesives and sealants provide excellent protection against moisture getting in and against corrosion. That's crucial for parts constantly exposed to harsh weather. They create a continuous, impenetrable seal.

Elena Bondwell:

Preventing water getting under the floor, for example.

Lucas Adheron:

Exactly. Stopping that kind of hidden corrosion you might find in older designs. And finally, these materials are engineered for harsh conditions.

Elena Bondwell:

Right. They're not just craft glue.

Lucas Adheron:

Definitely not. They're specially formulated to endure constant vibration, shock, extreme weather, think freezing, minus 40 Celsius, up to scorching, plus 80 Celsius. Plus, they often provide critical electrical insulation in sensitive areas, adding another layer of safety.

Elena Bondwell:

Wow. Okay. So it's a whole package of benefits driving this.

Lucas Adheron:

Oh, yes.

Elena Bondwell:

So it's clear these adhesives are everywhere now, but some of their applications are genuinely unexpected. You might not even realize where this glue is doing the heavy lifting. What are some of the most surprising places we find them?

Lucas Adheron:

Oh, absolutely. And thinking about the bigger picture, adhesives contribute in ways that fundamentally change how the train performs, often invisibly.

Elena Bondwell:

Like where?

Lucas Adheron:

Well, Take glued train windows. In modern high-speed trains, the windshields and the side windows are often glued directly to the body structure. It's a technique called direct glazing.

Elena Bondwell:

No frame.

Lucas Adheron:

Essentially, yes. And it's not just for looks, though it does look cleaner. It actually means the window itself becomes a structural part of the train body.

Elena Bondwell:

Wow. Strong enough for high speeds.

Lucas Adheron:

Strong enough to withstand incredible pressure pulses, like when entering tunnels at 300 kilometers per hour. Plus, it drastically improves aerodynamics and cuts down wind noise inside.

Elena Bondwell:

Okay, that's impressive. What about inside the train?

Lucas Adheron:

Yeah, seats and interiors. It's not just the exterior. Lots of interior elements are held by adhesives. Flooring and passenger coaches, for instance. is frequently glued down

Elena Bondwell:

why glue the floor

Lucas Adheron:

for a seamless finish mainly and to eliminate any loose screw heads that could become trip hazards over time even seat components

Elena Bondwell:

the seats themselves

Lucas Adheron:

from the foam cushions bonded to the frames to the fabric or leather covers often attached with high strength glue instead of visible bolts or staples

Elena Bondwell:

advantages

Lucas Adheron:

cleaner look definitely a quieter ride, because there are fewer things to rattle, and importantly, enhanced safety by removing hard metal fasteners from passenger areas where you might bump into them.

Elena Bondwell:

Huh. Never thought about glued seats. What else is quirky?

Lucas Adheron:

Well, here's a slightly quirky one. Attaching auxiliary equipment... Like

Elena Bondwell:

antennas and stuff.

Lucas Adheron:

Exactly. Antennas, GPS units, cable housings. Using adhesive avoids drilling holes through the roof.

Elena Bondwell:

Ah, preventing leaks.

Lucas Adheron:

Precisely. No holes means no potential water ingress. It simplifies installation and maintenance, too, and keeps the train absolutely watertight, even at high speeds and in rough weather.

Elena Bondwell:

Clever. Anything safety critical.

Lucas Adheron:

Definitely. Think about brake pads bonded. Not riveted. This is a critical safety application.

Elena Bondwell:

Brakes. They glue brake pads on.

Lucas Adheron:

They do now. In the past, brake shoes were riveted. Today, the friction material for train brakes is usually bonded with high-temperature adhesives, like phenolic or epoxy types, to the steel backing plate.

Elena Bondwell:

Is that better than riveting?

Lucas Adheron:

It provides more uniform stress distribution across the pad. And you can utilize the entire pad surface for braking, not just the area around the rivets. So yes, it contributes significantly to railway safety and reliability.

Elena Bondwell:

Okay, that's a big one. Are freight cars using this tech, too? Or is it mostly passenger trains?

Lucas Adheron:

Oh no, freight cars use adhesives, too. Even those heavy freight rail cars, which you might think of as purely mechanical beasts, they benefit as well. Newer refrigerated cargo box cars, for instance, they use bonded composite insulation panels.

Elena Bondwell:

For better insulation.

Lucas Adheron:

Exactly. Saves weight and improves thermal efficiency. It creates a continuous insulated shell without any bolt penetrations that could cause cold leaks. And specialized sealants are used to weatherproof seams and joints on things like hopper cars, protecting cargo-like grain from rain and contamination.

Elena Bondwell:

So it really is across the board from high-speed passenger trains to heavy freight.

Lucas Adheron:

It is indeed.

Elena Bondwell:

So these clearly aren't just variations of superglue we're talking about. It really sounds like there's a highly specific adhesive chemistry for every single job. A real marvel of materials. You're

Lucas Adheron:

absolutely right. The choice of adhesive is finely tuned to each specific application. It's like picking exactly the right specialized tool for a particular task.

Elena Bondwell:

So what kind of chemistries are we talking about?

Lucas Adheron:

When we talk about advanced chemistries, the rail industry relies on some pretty powerful compounds like methacrylate structural adhesives or MMAs. Think of MMA as the sort of speedy, versatile glue, good for quick, strong bonds on large surfaces. They offer high strength, strength, flexibility, and they cure rapidly at room temperature, which helps manufacturing speed.

Elena Bondwell:

Okay, what else?

Lucas Adheron:

Then you have epoxies. They're kind of the heavy-duty, rock-solid choice. You use those for critical structural points that demand very high strength and extreme resistance to weather and chemicals. Right. And then things like polyurethane-based adhesives or MS polymer sealants. They're valued more for their elasticity, their flexibility. So they're perfect for areas like ceiling window glass or expansion joints where you need some movement, but also a continuous seal.

Elena Bondwell:

A whole toolbox of glues. And who makes this stuff?

Lucas Adheron:

Well, behind these innovations are several leading manufacturers. These are the real pioneers in the field. The companies like Dow, DuPont, Hankel, Huntsman, they're at the forefront.

Elena Bondwell:

Big chemical names.

Lucas Adheron:

Exactly. They develop these specialized adhesive chemistries for pretty much every rail application imaginable. You'll find the products used for everything from sound damping and anti-slip flooring.

Elena Bondwell:

We talked about noise

Lucas Adheron:

reduction. Right. To crucial protection for electronics on board. And many of their formulations are specifically engineered to meet those really strict fire safety standards we'll probably talk about. They develop high-performance structural adhesives that actually replace mechanical fasteners, specialized solutions to reduce that noise and vibration, the NVH.

Elena Bondwell:

Henkel's Terrasin, you mentioned.

Lucas Adheron:

Exactly. And advanced fiber-resistant composite resin systems, which are vital for lightweighting things like battery housings on electric trains. Their collective innovation is really what drives the capabilities of modern rail.

Elena Bondwell:

So it's clearly not just about the chemical companies inventing these amazing glues, is it? There must be a whole support system. And you mentioned strict rules ensuring these trains are fundamentally safe. How does that whole ecosystem work.

Lucas Adheron:

Yeah, it's a highly specialized market. You're right.

Elena Bondwell:

Yeah.

Lucas Adheron:

And the pivotal role of technical distributors, it's absolutely critical here.

Elena Bondwell:

Distributors, like the wholesalers.

Lucas Adheron:

They are far more than just logistics providers, actually. Think of companies like Bodo Möller Chemie. They are specialist solution providers. They act as trusted partners for those major manufacturers we just mentioned, Dow, DuPont, Huntsman, Hankel. They basically bridge the gap between the cutting edge chemical development and the practical needs of the train manufacturers on the ground.

Elena Bondwell:

So they're the experts making Precisely.

Lucas Adheron:

They provide crucial technical advice, training for the assembly workers. They even conduct customer-specific application tests in their own labs.

Elena Bondwell:

They have labs for this.

Lucas Adheron:

Oh, yes. Like the one Bodo Möller Chemie has in Poland, which is certified to a key standard, DIN 6701-2. They ensure global reach, but with local presence and expertise. Their commitment to quality and safety is underlined by certifications like ISO 9001 and that industry-specific DIN 67012 for adhesive bonding in rail vehicle manufacturing.

Elena Bondwell:

Okay, DIN 67012. That sounds important.

Lucas Adheron:

It is. And that brings us to another paramount aspect, the criticality of fire safety standards, specifically EN 455-452.

Elena Bondwell:

Ah, the fire standard. You mentioned it earlier.

Lucas Adheron:

Yes. This European standard is mandatory, absolutely mandatory for all materials and components used in rail vehicles across Europe and widely influential elsewhere. It was introduced to unify standards and really raise the level of protection against onboard fire incidents.

Elena Bondwell:

Okay. And how do these standards directly impact our safety as passengers. You mentioned hazard levels. What do those actually mean for us sitting on the train?

Lucas Adheron:

It's designed specifically for your safety. Railway vehicles get classified into three hazard levels, HL1, HL2, HL4. HL1,

Elena Bondwell:

2, and 3. Based on?

Lucas Adheron:

Based on their design and how they operate. For example, a key factor is how frequently and for how long they spend running through tunnels.

Elena Bondwell:

Ah, because escape is harder in a tunnel fire.

Lucas Adheron:

Exactly. So if you're on a long distance high speed train that frequently goes through lengthy tunnels, that vehicle and every single material in it from the seat fabric to the window adhesive, the flooring, everything must meet the highest standard hazard level three.

Elena Bondwell:

Got it. Highest risk, highest standard.

Lucas Adheron:

Right. And materials are also categorized into 26 distinct product requirements, R1 to R26, depending on where they are used. R1 might be for interior wall surfaces, R26 for small electronic components.

Elena Bondwell:

So adhesives have to meet specific R numbers too.

Lucas Adheron:

Absolutely. Adhesives must undergo rigorous testing. They look at things like flame spread, smoke opacity, how much smoke it produces, and the toxicity of that smoke. They have to meet these very precise fire, smoke, and toxicity criteria for their specific application And

Elena Bondwell:

this isn't optional.

Lucas Adheron:

Not at all. Compliance isn't merely a suggestion. It's a strict prerequisite for selling trains or components in Europe. And this pressure drives continuous innovation towards inherently safer materials.

Elena Bondwell:

Okay, that's reassuring. So looking ahead then, what does all this mean for the future of rail transport? What are the next big leaps we might see in adhesive technology? And what challenges still need to be tackled?

Lucas Adheron:

Yeah, the rail industry is definitely transforming rapidly. It's driven by innovation, the push for sustainability, and constant demands for enhanced performance.

Elena Bondwell:

So what's next for the adhesives themselves?

Lucas Adheron:

In terms of technological advancements, we're seeing ongoing innovation in high-performance adhesives, things with even better durability, better multi-substrate adhesion, sticking different things together even more reliably, especially with materials like those MMAs we talked about for joining mixed materials like composites and metals.

Elena Bondwell:

Any really futuristic stuff.

Lucas Adheron:

While there's cutting-edge research into nanomaterials being incorporated into adhesives, bio-based polymers, trying to move away from purely petrochemical sources, and things like dual cure systems.

Elena Bondwell:

Dual cure.

Lucas Adheron:

Yeah, systems that might use UV light for a quick initial hold, rapid fixturing, and then a secondary chemical cure for full strength. That could enable even faster assembly lines.

Elena Bondwell:

Interesting. What about sustainability? That seems key now.

Lucas Adheron:

Absolutely. A significant trend is the push for sustainable and eco-friendly adhesives. We're seeing more bio-based formulations using natural materials, and an increased focus on using recycled content in the adhesives themselves.

Elena Bondwell:

Like the trains themselves using recycled material.

Lucas Adheron:

Exactly. Allsman's Metropolis Metro Trains, for example, already incorporate about 28% recycled materials overall. The adhesives need to follow suit. There's also the rise of what you might call smart adhesives. Smart glue. Well, maybe not thinking glue, but multifunctional sealants. And also, specialized adhesive tapes are becoming huge, used for everything from masking during painting to managing cables, damping noise, even labeling, all contributing to more efficient, sometimes automated manufacturing.

Elena Bondwell:

Tapes are adhesives too, of course. That's incredible progress. But, you know, every innovation often comes with its own set of challenges. What are the major hurdles engineers are grappling with now?

Lucas Adheron:

You're right. There are significant hurdles. We mentioned multi-material bonding. It's still complex. Different materials expand and contract differently with temperature, have different surface properties. Getting a durable long-term bond is always an engineering challenge.

Elena Bondwell:

Makes sense.

Lucas Adheron:

But a major challenge, and this really touches on the larger implications of this technology, is the recyclability of bonded components.

Elena Bondwell:

Ah, the end-of-life problem.

Lucas Adheron:

Exactly. While metals from trains are highly recyclable, Adhesives, especially when they're bonding different materials together in these complex assemblies, create a paradox.

Elena Bondwell:

A paradox.

Lucas Adheron:

How so? They enable incredibly sustainable design during the train's operational life through lightweighting better fuel efficiency. But they can really complicate recycling at the end of life.

Elena Bondwell:

Because you can't easily separate the materials.

Lucas Adheron:

Precisely. Composites and varied plastics, once they're bonded together, are particularly difficult to separate and recycle efficiently. Often, this bonded material ends up as just shredder residue, which goes to landfill.

Elena Bondwell:

So the very thing that makes them sustainable in use also makes them harder to recycle. That's a fascinating and really important paradox for the industry to solve.

Lucas Adheron:

It is. It highlights the urgent need for what they call debondable adhesives or easily separable adhesive systems to support a true circular economy for trains.

Elena Bondwell:

Right, glues you can unglue somehow when needed.

Lucas Adheron:

That's the goal. And beyond that, we also continue to see challenges like fluctuations in raw material prices, which impacts production costs for these specialized chemicals. And there's always a continuous need for customized solutions because the requirements across different rail applications, high speed, metro, freight, are just so specific.

Elena Bondwell:

So constant innovation is still needed on multiple fronts.

Lucas Adheron:

Absolutely.

Elena Bondwell:

Well, as you can see, adhesives are clearly not just glue anymore. Not by a long shot. They are fundamental high-tech components that are quietly enabling the rail systems of tomorrow, making them faster, safer, more efficient, in ways we rarely even consider when we step on board.

Lucas Adheron:

Indeed. And as we continue to push for faster, lighter, greener trains, the question becomes... What unseen innovations in bonding technology will define the future of transport? And critically, how will we balance the incredible advantages these materials offer with that crucial challenge of managing their end of life responsibly?

Elena Bondwell:

Definitely something to mull over next time you're on a train, isn't it? Thanks so much for joining us for this deep dive.

People on this episode

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Elena Bondwell

Host
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Lucas Adheron

Co-host

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