What is the difference between ACM and AEM rubber?

Choosing the wrong rubber for automotive and industrial parts can lead to swelling, cracking, or even seal failure. I’ve worked with clients who faced these issues—usually because they didn’t know the real differences between ACM and AEM.

ACM (acrylic rubber) and AEM (ethylene acrylate rubber) are both oil- and heat-resistant elastomers, but AEM offers better flexibility at low temperatures and higher durability in demanding environments.

Knowing which material to use ensures longer service life and lower maintenance in gaskets, hoses, and seals.

What is ACM rubber?

ACM stands for acrylic rubber. This material is widely used in automotive and industrial seals where resistance to hot oil, oxygen, and ozone is needed.

ACM provides good resistance to hot oils and oxidation, making it ideal for transmission gaskets and automotive hoses.

Limitations: ACM tends to harden and crack at low temperatures. It’s not suitable for dynamic sealing in cold climates.

What is AEM rubber¹?

AEM stands for ethylene acrylate rubber² (also called Vamac®, a DuPont trade name). It is a copolymer of ethylene and methyl acrylate.

AEM rubber combines good oil resistance with much better flexibility at low temperatures and strong mechanical properties.

AEM is chosen for turbocharger hoses, intercooler couplings, crankcase ventilation hoses, and demanding gaskets—especially in parts exposed to wide temperature swings.

How does chemical structure set ACM and AEM apart?

Production delays from failed seals can often be traced to a mismatch in material composition. Buyers sometimes overlook the importance of polymer chemistry—then spend weeks troubleshooting.

ACM is made from acrylic acid, resulting in a polar rubber with strong oil resistance. AEM, made from ethylene and methyl acrylate, is less polar but has better flexibility and aging resistance.

Let’s break down what this means in practice. ACM, or acrylic rubber, is built from ethyl or butyl acrylate monomers. This structure creates a material that resists swelling and degradation when exposed to automotive oils and hydraulic fluids. I’ve specified ACM for compressor applications exposed to aggressive oil blends, but it doesn’t perform well with water or antifreeze.

AEM is made from ethylene and methyl acrylate, producing a backbone with better weathering and flexibility. AEM rubber is a top choice for dynamic seals or parts that see repeated flexing and ozone exposure. Here’s a practical comparison:

Which rubber resists heat and chemicals better?

If your HVAC or engine application faces extreme heat, standard rubbers break down fast. You need a material that keeps sealing as lines get hot.

AEM rubber provides better high-temperature stability, ozone durability, and long-term aging than ACM. ACM is best chosen for oil-heavy environments with moderate heat.

In engine seals we tested for a Dutch automotive OEM, ACM began degrading after long heat exposure—especially if coolants were present. AEM kept its shape and flexibility nearly 20% longer at 155°C during continuous use. Both resist oil, but AEM outperforms ACM in outdoor, ozone-rich, or high-UV⁶ settings.

How do ACM and AEM affect cost, usage, and supply chain risk?

Budget overruns and missed deadlines often come from shortcuts in material selection. Jet and his team look at more than the datasheet—they consider availability, processing, and total lifecycle cost.

ACM rubber is usually more affordable and widely stocked, but AEM offers longer service intervals, reducing long-term downtime. Regional supply and certification requirements may shift the balance.

From my purchasing experience, ACM usually costs 10–20% less and is easier to source. However, if EU environmental standards⁷ are strict, AEM’s extra upfront cost is offset by less frequent replacement.

AEM also processes better for complex, flexible gaskets⁸. The main limitation for ACM is that it isn’t always accepted by regulators, while AEM clears most industry certifications in automotive and HVAC⁹.

ACM vs AEM: Which should you use?

If you need a seal for a static part in a warm, oily environment, ACM is usually enough.
If you require flexibility at low temperatures, exposure to outdoor weather, or dynamic sealing, AEM is the better choice.

Typical applications

• ACM: Transmission gaskets, automatic gearbox seals, oil-resistant static seals, timing belt covers.
• AEM: Turbocharger hoses, air intake and intercooler hoses, crankcase ventilation, flexible engine gaskets, dynamic seals in harsh environments.

Julong Rubber supplies both ACM and AEM compounds for custom-molded parts and gasket production.

Conclusion

ACM and AEM are both good for oil and heat resistance, but AEM offers far superior low-temperature flexibility and durability. Pick AEM if your application sees cold, weather, or movement; choose ACM for static, oil-resistant seals at moderate cost.