Adhesion Matters
Adhesion Matters pulls back the curtain on the remarkable world of adhesives—the invisible technologies quietly revolutionizing everything from smartphones and EVs to Hollywood effects and wind turbines. We guide listeners on a deep-entangled journey through innovation, sustainability, and the surprising human stories behind the products that hold our modern life together.
Adhesion Matters isn’t just about chemistry—it’s a storytelling lens on how sticky stuff shapes our world. Every episode reveals that adhesives do more than bind—they enable durability, safety, and innovation across industries. Tune in if you’re curious about the overlooked tech that really holds things together.
Adhesion Matters
Thermal Runaway: How Adhesives Help Stop EV Batteries from Exploding
What if one tiny cell could tip a whole EV battery into an uncontrollable blaze? In this high-voltage episode of Adhesion Matters, we expose the silent, high-stakes role adhesives play in preventing—and even containing—thermal runaway.
Inside the Episode:
- The Hidden Danger of EV Batteries
Thermal runaway isn’t just a buzzword—it’s a real, rapid chain reaction where one cell overheats and ignites its neighbors. Learn just how extreme this process can get (hint: temperatures can surge to hundreds of degrees in seconds). - Adhesives as the Unsung Heroes
These aren’t your typical craft glues. On the contrary, they’re advanced, multi-functional materials engineered to:- Act as thermal firewalls between cells (cell-to-cell barriers),
- Provide electrical insulation and prevent arcing,
- Damp structural stress and absorb shock,
- Resist flames and seal gases—keeping cells from “speaking fire” to each other.
- Battling the Unexpected: A Six-Point Safety Strategy
Discover how adhesives tackle literally everything—from mechanical impacts and electrical faults to the roar of venting particles and the creep of heat through air gaps. - Material Meets Design Meets Scalability
We unpack how manufacturers like DuPont, Henkel, Dow are tailoring formulations to fit each zone’s needs: thermally conductive yet electrically insulating epoxies; injectable polyurethane barriers; silicone gap-fillers built for flexibility and fire defense; and even the emerging tech of debond-on-demand for future recyclability.
Why It Matters:
This episode shows how the very safety of electric vehicles hinges on adhesives doing exponentially more than you ever imagined—balancing heat, shock, gas, flame, voltage, and even sustainability. If you’re into EV innovation, battery science, or just fascinated by the materials that make our future safer, this one will electrify your perspective.
The global shift to electric vehicles, it's really speeding up, isn't it? And when you think about them, your mind probably goes straight to range or charging time, maybe those sleek designs.
Lucas Adheron:The obvious things.
Elena Bondwell:Exactly. But there's this crucial kind of unseen element underpinning it all. safety. And especially with EV battery safety, there's this unsung hero doing some incredibly heavy lifting. Absolutely. Today, we're going to do a deep dive into the surprising multifunctional role of adhesives in electric vehicle batteries. I mean, these aren't just, you know, sticky tapes. They are critical enablers for mitigating something called thermal runaway.
Lucas Adheron:That's right. And our mission here really is to unpack how these specialized adhesive solutions have well, they've evolved way beyond just being bonding agents. They become completely indispensable components. We're talking comprehensive thermal management, robust electrical insulation, better structural integrity, and proactive fire safety inside the battery pack.
Elena Bondwell:So they prevent and contain.
Lucas Adheron:Exactly. They work on both ends, stopping thermal events from starting. And if one does kick off, limiting how far it spreads.
Elena Bondwell:Okay. And for this deep dive, we're drawing from some really detailed reports on these adhesive technologies and also looking at the role of companies like Bodo Möller Chemie in making it all work.
Lucas Adheron:Yeah, some fascinating stuff in there.
Elena Bondwell:So let's unpack this first bit. For anyone needing a refresher, what exactly is thermal runaway in a lithium ion battery? Why is it such a huge safety concern for EVs?
Lucas Adheron:Okay, so thermal runaway is essentially an uncontrollable self-heating state. It happens within a single lithium ion battery. one
Elena Bondwell:cell.
Lucas Adheron:Start to one cell. Yeah. But once it kicks off, it can escalate incredibly fast. We're talking extreme temperatures, sometimes up to like a thousand degrees Celsius.
Elena Bondwell:Wow.
Lucas Adheron:Yeah. And that leads to violent cell, venting gases, escaping forcefully smoke and critically fire. Now, an event in just one cell might be manageable, but the real danger is how quickly it can spread, propagate throughout the entire battery pack. And that's when it becomes a major, major safety issue for the vehicle and, of course, everyone inside.
Elena Bondwell:That's a pretty intense scenario, and it connects to something else. We all want more range, faster charging in our EVs. That constant push for better performance, does that actually make this thermal runaway risk higher?
Lucas Adheron:That's a really sharp question. There's definitely an inherent tension there. The drive for higher energy densities, which is exactly what gives us that longer range and quicker charging it, directly correlates with an increased intrinsic thermal runaway risk.
Elena Bondwell:Intrinsic meaning it's just baked into the chemistry.
Lucas Adheron:Pretty much. Think about advanced cathode chemistries like these nickel-rich layered oxides. They just pack more energy into the same space. And this sets up a kind of positive feedback loop.
Elena Bondwell:How does that work?
Lucas Adheron:Well, so you get an initial temperature increase could be from anything, a small D Maybe a bit of overcharging. That extra heat speeds up the exothermic chemical reactions inside the cell.
Elena Bondwell:Exothermic meaning they produce heat.
Lucas Adheron:Exactly. So those reactions generate more heat, which then makes the temperature climb even faster, which speeds up the reactions again. And you see how it runs away. A
Elena Bondwell:vicious cycle.
Lucas Adheron:Completely. And this is where adhesives play such a strategic role. They can be designed to help dissipate that heat, get it out and away from the cell, or they can provide thermal insulation to act like a barrier, essentially breaking or at least dramatically slowing down that self-accelerating loop.
Elena Bondwell:Okay, that makes sense. So if we're trying to prevent these things from even starting, what are the usual suspects? What typically kicks off thermal runaway in a cell?
Lucas Adheron:Well, there are generally four main root causes, and it's quite interesting how adhesives can play a role in mitigating pretty much all
Elena Bondwell:of them. All right, let's hear them.
Lucas Adheron:First up is mechanical abuse. I think crushing, puncturing, a big impact like in a crash, or even just constant heavy vibration. Any of that physical damage can compromise the cell's internal separator, that thin layer keeping things apart. If that fails, you get internal short circuits, and boom, rapid heating. Adhesives help here by providing real structural integrity, absorbing shock, acting as compression pads. They directly counter those physical forces.
Elena Bondwell:So they make the battery tougher, basically.
Lucas Adheron:In a way, yes. Second is electrical stress. Things like overcharging, discharging too deeply, or an external short circuit somewhere. Right. These create uncontrolled electrical current. which again leads to heat. Now, adhesives don't stop the electrical fault itself. They're not a fuse. No, exactly. But they provide really robust electrical insulation. They stop unintended current paths, prevent arcing between components, or secondary shorts that could make the heating much worse.
Elena Bondwell:What's third?
Lucas Adheron:Third is thermal exposure. Just being in extremely hot or cold environments for too long can mess with the cell's stability.
Elena Bondwell:Makes sense.
Lucas Adheron:So here you need adhesives that have a really wide and stable operating temperature range. Typically something like minus Minus 40 Celsius up to 150 C. Some silicones can even go up to 200 C. They need to maintain their properties, not degrade, because adhesive degradation could potentially lead to other faults.
Elena Bondwell:Okay. Stable across temperatures. The last one.
Lucas Adheron:The fourth one is manufacturing defects and internal failures. These can be tiny microscopic things, impurities in the materials, maybe uneven coatings during production, or slight damage to that separator layer we mentioned.
Elena Bondwell:Hard to catch sometimes, I imagine.
Lucas Adheron:Very. And this is where things like conformable gap fillers, a type of adhesive, play a crucial role. They fill in tiny irregularities, make sure heat transfers evenly, and prevent those localized hot spots from forming, which could otherwise be the starting point for runaways.
Elena Bondwell:Okay, so adhesives are working against mechanical, electrical, thermal, and internal defect issues. It's quite a job description. It really is. But even if an event does start in one cell, you said the real danger is when it spreads. How does that happen? How does this thermal propagation move through a densely packed battery.
Lucas Adheron:Right, propagation is the key danger. It's a complex chain reaction, and it happens through several different mechanisms. The most direct one is just cell-to-cell conduction.
Elena Bondwell:Heat moving directly through contact.
Lucas Adheron:Exactly. Heat transferring straight from the compromised cell to its immediate neighbors. Now, for pouch or prismatic cells, that's usually two neighbors. But for cylindrical cells, like the ones you see in some EVs, it could be up to six neighbors touching.
Elena Bondwell:More paths for the heat.
Lucas Adheron:Precisely. And adhesives, used as cell-to-cell barriers, sometimes called CTC barriers, act like critical firewalls. They're designed either to insulate and block the heat, or sometimes to redirect it towards a cooling system.
Elena Bondwell:Okay, direct contact. What else?
Lucas Adheron:Then you have primary and secondary combustion and gas management. This is where it gets really violent. Hot, fuel-rich gases get ejected forcefully from the failing cell. Yes, but these gases are hot and flammable. They can spread and ignite adjacent cells directly, and And this brings up a really important point. What about the risk of those toxic hot gases getting into the passenger compartment?
Elena Bondwell:Yeah, that's critical.
Lucas Adheron:So the adhesives used here need serious flame retardancy. They have to resist catching fire themselves and slow down the spread. They also have to be strong enough to withstand the pressure of these venting gases. And they contribute to sealing the whole battery pack enclosure, directing that gas flow safely away, perhaps through design vents. Think of things like Henkel's fire protective coatings.
Elena Bondwell:Okay, so managing the fire and the gas. Intense.
Lucas Adheron:Very. Then there's hot particulate ejection. We're talking tiny bits of molten metal, plastic, maybe copper being shot out at high velocity from the failing cell.
Elena Bondwell:Like shrapnel.
Lucas Adheron:Essentially, yes. So adhesives or coatings applied with adhesives need to act as robust physical barriers here. They need to resist being punctured or abraded by these particles. This is where you see things like ablative coatings. They basically sacrifice a layer to absorb the energy and trap those particles.
Elena Bondwell:Ablative, like on spacecraft radios. Similar
Lucas Adheron:principle, yeah. Absorbing energy by sacrificing material. Now, here's where the engineering gets really, really tricky. Secondary conductive pathways.
Elena Bondwell:What does that mean?
Lucas Adheron:Think about the other components inside the pack. bus bars, connecting cells, cooling plates. These are often made of highly conductive metals like aluminum or copper.
Elena Bondwell:Right, to move electricity or heat efficiently.
Lucas Adheron:Exactly. But that high conductivity means they can unintentionally act like heat tunnels, bypassing those primary C2C barriers we talked about, and carrying heat rapidly to other parts of the pack.
Elena Bondwell:Ah, so the solution becomes part of the problem.
Lucas Adheron:It can be if not managed. So adhesives are strategically applied to insulate these pathways, or some Sometimes they're used to bond materials together that deliberately break these thermal bridges. It really highlights this complex balancing act. You need electrical conductivity for performance, but you have to manage thermal conductivity for safety.
Elena Bondwell:That is nuanced. Any other ways it spreads?
Lucas Adheron:One more main one. Natural convection across air gaps. If there are air spaces within the pack, hot combustion products and gases can simply circulate via air currents, spreading the heat around.
Elena Bondwell:So filling the gaps helps.
Lucas Adheron:Precisely. Adhesives used for sealing the main enclosure and also gap fillers used within the pack help minimize these air pathways, essentially trapping hot gases and slowing their spread.
Elena Bondwell:It sounds incredibly fast and chaotic when it happens. You mentioned cooling systems. What about the vehicle's active liquid cooling system? Isn't that supposed to handle heat? Why isn't it enough to stop this kind of rapid escalation?
Lucas Adheron:That's a great point. Active cooling systems are absolutely vital for normal battery operation, keeping temps in the optimal range. But during the initial super- Thank you. Pumps, hoses, radiator might be damaged, compromised, or simply lack power.
Elena Bondwell:Right. It might not even be working.
Lucas Adheron:Exactly. And that really underscores why passive safety solutions like these specialized adhesives and barriers are so critical. They are the first line of defense. They provide intrinsic, built-in protection that works immediately without needing external power or complex electronic controls. They're always on.
Elena Bondwell:Okay. So they're the immediate passive safety net. It's clear these are way more than just, you know, glue. Let's really break down their core functions. What are these adhesives doing in there to mitigate thermal runaway? This is where the unsung hero part really comes in, isn't it?
Lucas Adheron:Absolutely. This is where you see their incredible multifunctionality. First off, there's heat dissipation and thermal conductivity. We have thermally conductive adhesives, often called TCAs. Their job is to create a really efficient thermal pathway between the individual cells and the cooling system components, like cold plates. They fill in microscopic air gaps, which are terrible heat conductors, and efficiently transfer heat away from the cells. And crucially, they do this while still providing electrical insulation.
Elena Bondwell:How conductive are we talking?
Lucas Adheron:It varies quite a bit, depending on the chemistry and fillers used. You might see values around 0.65 watts per meter Kelvin, that's the unit WMK for some polyurethanes, but you can get up to, say, 7.9 WMK, or even higher for things like silver-filled epoxies, which are extremely conductive thermally.
Elena Bondwell:Okay, so it Moving heat is key. What else?
Lucas Adheron:Second, as we touched on, is electrical insulation and short circuit prevention. In a high voltage battery pack, this is absolutely critical. Adhesives create dielectric barriers, meaning they don't conduct electricity well, providing accidental electrical contact between cells, modules, or the casing. They stop arcing. You need materials with high breakdown voltage and good dielectric strength here.
Elena Bondwell:Makes sense. High voltage needs good insulation.
Lucas Adheron:Definitely. Third, they provide structural integrity and mechanical reinforcement. Instead of just spot welds or mechanical fasteners, adhesives create continuous bond lines. This distributes stress more evenly, making the whole pack much more durable and improving its performance in a crash.
Elena Bondwell:So they actually make the battery structure stronger.
Lucas Adheron:Significantly. This even enables advanced designs like cell-to-body or CTB, where the battery pack itself becomes part of the vehicle's structure, replacing heavier traditional frame components. Adhesives make that possible. And beyond just strength, they protect against chemical attack, UV degradation, humidity, and ensuring long-term reliability.
Elena Bondwell:Okay, strength and durability. That's huge. What's next?
Lucas Adheron:Fourth is fire resistance and flame retardancy. This is direct safety. Egress time, right. Wow, active firefighting almost. In
Elena Bondwell:a
Lucas Adheron:passive way, yes. Fifth, a really interesting one, accommodation of cell expansion and contraction. Lithium ion cells actually breathe slightly. They change volume a tiny bit during charge and discharge cycles.
Elena Bondwell:I didn't know that.
Lucas Adheron:Yeah, it's a well-known phenomenon. If the bonding is too rigid, this constant mechanical stress can cause failures over time, debonding, cracking. So you need flexible adhesive formulations, things like silicones, polyurethanes, certain acrylic foam tapes that can absorb this stress, move the cell while still maintaining a strong bond and performing their other functions.
Elena Bondwell:So they need to be strong and flexible.
Lucas Adheron:Exactly that balance. And finally, number six is in The adhesive itself and the bond it creates needs to resist moisture ingress, attack from chemicals like battery electrolytes or coolants, and degradation from UV radiation over the battery's entire lifespan, which could be 10, 15 years or more. This ensures the adhesive keeps doing all its other jobs effectively.
Elena Bondwell:It really is like a tiny multi-tool inside the pack. Heat management, insulation, structure, fire safety, flexibility, environmental sealing.
Lucas Adheron:It's a demanding list of requirements for one material system.
Elena Bondwell:No kidding. If you had to pick one function that seems the most, I don't know, counterintuitive or surprising for an adhesive, what would it be? Hmm.
Lucas Adheron:That's a good question. Maybe the combination of providing significant structural reinforcement while simultaneously needing to be flexible enough to accommodate that cell breathing.
Elena Bondwell:Right. You think structural means rigid.
Lucas Adheron:Typically, yes. But here... The engineering is so sophisticated that these materials provide immense bond strength and stiffness in certain directions, contributing to the pack's overall rigidity and crash worthiness. Yet they have enough flexibility or give to handle those small cyclical cell movements without failing. That combination is pretty amazing, I think.
Elena Bondwell:That really does highlight the advanced material science involved. Okay, so given all these critical jobs, where are these specialized adhesives actually put inside the battery pack? It must be a very carefully engineered layout.
Lucas Adheron:Oh, absolutely. The placement is highly strategic. You'll find them used as cell-to-cell barriers, like we discussed. Those crucial firewalls or insulators sitting directly between adjacent cells to stop or slow thermal propagation.
Elena Bondwell:Right, the first line of defense.
Lucas Adheron:Definitely. They're also vital for cell-to-module and module-to-pack bonding. This is about securely holding the cells together within their modules and then holding those modules securely within the main battery pack enclosure. This contributes massively to structural integrity and crash performance.
Elena Bondwell:Holding everything together tightly.
Lucas Adheron:Exactly. Then, for integration with cooling systems, you have those thermally conductive adhesives and gap fillers that TIMS thermal interface materials. They're essential for filling those microscopic air gaps between the cells and the cooling plates, or heat sinks, ensuring that heat can get out efficiently.
Elena Bondwell:Maximizing the cooling effect.
Lucas Adheron:Precisely. You also see adhesives used in or to bond compression pads and anti-swelling solutions. These are often flexible, pad-like materials placed between cells to manage the mechanical stress from that expansion-contraction, and they can sometimes offer additional thermal runaway protection too. The adhesive holds them reliably in place.
Elena Bondwell:Managing the breathing.
Lucas Adheron:Yes. And finally, they're critical for enclosure sealing and structural reinforcement. Adhesives create strong, durable, often moisture resistant seals around the main battery pack casing. This protects the internals from the environment, helps contain internal gas pressure during a thermal event, and can even add to the overall structural rigidity of the pack itself.
Elena Bondwell:So they're really integrated everywhere, performing different roles in different spots.
Lucas Adheron:It's a system-level approach. You need the right adhesive in the right place, performing the right combination of functions.
Elena Bondwell:This sounds like a field with some serious innovation happening. Who are the key players? Who's actually developing and making these advanced adhesive solutions?
Lucas Adheron:Yeah, there's a lot of R&D. Several major chemical companies are leaders here. For example, DuPont. They have products like Betamida structural adhesives, which are widely used for that structural integrity piece and enabling those cell-to-body designs. Okay, DuPont. They also offer Betatictim Tim's thermal interface materials. Interestingly, some of these are formulated to be disocyanate and silicone-free, which can be important for EHS reasons. And they're designed with low pull-out force.
Elena Bondwell:Meaning?
Lucas Adheron:Meaning it's easier to disassemble the battery pack for repair or recycling later on. That connects directly to the whole circular economy push, which is a big deal now. And they also have things like Beta Force 2800 TC, specifically aimed at handling the heat from fast charging.
Elena Bondwell:Ah, tackling specific challenges. Who else?
Lucas Adheron:Henkel is another major player. They have Loctite products you might recognize. For batteries, things like Loctite TLB 9300 APSI, it's an injectable two-part polyurethane. Offers good thermal conductivity, around 3 WMK, plus structural bonding and electrical insulation. And it cures at room temperature.
Elena Bondwell:Injectable sounds useful for manufacturing.
Lucas Adheron:Exactly. It signals a focus on precision application, maybe robotics, automation in high-volume production. Henkel also has high-strength epoxies like Loctite EA9497 and a whole range of fire-protective coatings. Loctite EA9400 is an intumescent one. Loctite FPC5060 is a water-based inorganic type. Lots of options.
Elena Bondwell:Okay, Henkel. Any others?
Lucas Adheron:Dow is definitely significant, too. They offer dowsile silicone products like TC2035, another thermal conductor around 3.3 WMK. And they have their Voratron line of polyurethane gap fillers like the 1000 series, which are known for having a very low squeeze force.
Elena Bondwell:Why is low squeeze force good?
Lucas Adheron:It makes them really easy to dispense accurately and quickly in automated manufacturing lines, reducing stress on the components and the dispensing equipment. It's all about optimizing for mass production.
Elena Bondwell:Right. Efficiency matters. So we have these big manufacturers creating the chemistries, but You mentioned distributors playing a role, too, like Bodo Möller Chemie. How do they fit in?
Lucas Adheron:Ah, yes. Companies like Bodo Möller Chemie are absolutely crucial. They're much more than just distributors. Think of them as global full line suppliers specifically focused on future mobility solutions. They've been involved in like over 2,000 projects worldwide in this area.
Elena Bondwell:Wow, that's a lot of experience.
Lucas Adheron:It really is. They act as a vital development partner for both the adhesive manufacturers and the automotive OEMs or battery makers. They provide deep technical expertise, R&D support. They can do customer-specific application testing in their labs, and they handle complex global logistics.
Elena Bondwell:So they bridge the gap between the chemical company and the car company.
Lucas Adheron:Perfectly put. They essentially translate the complex chemical property of these adhesives into practical, usable, technical design data that engineers can actually work with. They have strong partnerships with all the majors, Hankel, Huntsman, Dow, DuPont. And they're also involved in bringing new solutions to market, like innovative polyurethane structural phones for cell separation that also improve crash stability, reduce vibration, and add thermal insulation.
Elena Bondwell:And you mentioned something really interesting earlier, debonding.
Lucas Adheron:Yes. This is a really exciting emerging area. Debonding on demand. They're working with special primers Why is that important? Think about repair and end-of-life recycling. Right now, glued together battery packs can be really hard to take apart non-destructively. De-bonding on demand is a massive step towards a true circular economy for batteries, making them easier to repair, refurbish, and recycle components from. It's about sustainable design right from the start.
Elena Bondwell:That sounds like a potential game changer for the industry's footprint.
Lucas Adheron:It really could be.
Elena Bondwell:Well, this has been an absolutely incredible deep dive. It's just eye-opening how something we might think of as simple glue is actually this incredible sophisticated multifunctional material that's totally central to the safety, the performance, and even the future sustainability of electric vehicles.
Lucas Adheron:You summarized it perfectly. These materials are working silently, constantly behind the scenes. They're dissipating heat. They're insulating high voltages, providing structural backbone, resisting fire, accommodating those tiny cell movements, protecting against the environment. They truly are the hidden heroes, making sure our electric future is a safe one.
Elena Bondwell:So next time you hear about the latest EV innovation, faster charging, longer range, remember these silent, sticky heroes working deep inside the battery pack. It really makes you wonder, doesn't it? What other invisible materials like these are secretly revolutionizing industries all around us? And how will their roles continue to evolve as technology pushes forward?
