WACKER ELASTOSIL N2189 vs N2034 – Which RTV-1 silicone to choose for UL 94 V-0 applications?
In industrial applications, choosing a technical silicone often starts with a single requirement: fire resistance. For electronic, electrical, automotive, or industrial components, the flexibility and temperature resistance of a sealant alone may not be enough. The material must also ensure an adequate level of safety in case of contact with a flame. That is why the UL 94 V-0 classification is one of the key parameters that designers and technologists look for.
However, an important question arises: if two silicones meet the UL 94 V-0 requirements, can they be used interchangeably? In the case of WACKER® ELASTOSIL® N 2189 and ELASTOSIL® N 2034, the answer is: not necessarily. Both are one-component moisture-curing RTV-1 silicones, and both offer flame-retardant properties in accordance with UL 94 V-0, but their rheology, application method, and performance characteristics are distinctly different.
It is the difference between a non-sag material and a self-leveling silicone that makes the choice of the right product dependent not only on the required flammability rating, but also on the component's geometry, the application method, and the expected behavior of the material before curing.
UL 94 V-0 – What does it actually mean?
UL 94 is one of the most commonly used flammability classifications for materials used in electrical and electronic devices. The V-0 rating signifies a high level of resistance to flame propagation under a specific test method. In practice, meeting UL 94 V-0 is especially critical where the material is located near components that may generate heat, or where safety requirements restrict the use of standard, flammable materials.
It is worth emphasizing, however, that UL 94 V-0 does not tell the whole story about a silicone. Flammability classification is just one parameter. Two products can have the same UL 94 rating and behave completely differently during application. One might stay exactly where it was applied, while the other might spread over the surface and level out on its own.
And this is exactly where ELASTOSIL® N 2189 and ELASTOSIL® N 2034 begin to differ significantly.
ELASTOSIL® N 2189 – When the silicone must stay exactly where applied
ELASTOSIL® N 2189 is a black, one-component RTV-1 silicone utilizing a neutral alkoxy curing system. The material cures at room temperature upon exposure to atmospheric moisture and forms a flexible silicone rubber after curing.
One of its most important features is its non-sag nature, meaning it does not slump after application. This is a crucial property when sealing vertical or inclined surfaces, and wherever the component's geometry requires the applied layer to be precisely maintained. WACKER also highlights its good primerless adhesion to many substrates, particularly die-cast magnesium, and its strong resistance to mineral oils. The product has a UL 94 V-0 flammability rating and a recommended operating temperature range from -45°C to +200°C.
N 2189 is therefore a material perfectly suited for situations where the sealant must retain its geometry post-application. This is vital in technical seals and processes where the thickness and placement of the material layer affect the final result.
The product is used in Formed-In-Place Gasket (FIPG) applications, in the automotive and industrial sectors, and for sealing components exposed to mineral oils.
ELASTOSIL® N 2034 – When the material should spread
ELASTOSIL® N 2034 is also a one-component alkoxy-based RTV-1 silicone that cures upon exposure to airborne moisture. However, the key difference becomes apparent immediately during application.
N 2034 is a self-leveling material. This means that after application, the silicone flows over the surface, helping to achieve a more uniform coating. WACKER describes N 2034 as a low-viscosity silicone and highlights its flame-retardant properties in accordance with UL 94 V-0. The product also demonstrates excellent primerless adhesion to many substrates.
This represents a completely different approach to application compared to N 2189. It is not a matter of one product being "better" and the other "worse." Their respective advantages become apparent under different operating conditions.
If the design requires a bead or layer of silicone to hold its shape in a specific location, the non-sag property of N 2189 is a major advantage. If, however, the goal is to cover a surface as evenly as possible by utilizing the material's ability to flow naturally, the characteristics of N 2034 will be far more appropriate.
N 2189 or N 2034 – The biggest difference isn't the UL 94 rating
At first glance, both products may seem very similar. Both are RTV-1 silicones, both use an alkoxy system, both cure via moisture, and both offer a UL 94 V-0 flammability rating. In practice, however, their behavior during application is entirely different.
N 2189 was developed as a non-sag material, while N 2034 was formulated as a self-leveling material. In the current WACKER RTV product selection guide, N 2189 is described as an alkoxy-curing, oil-resistant, UL 94 V-0 silicone, whereas the documentation for N 2034 emphasizes its self-leveling nature, low viscosity, and flame-retardant properties.
A simple rule of thumb can be adopted:
This difference can be more significant for production technology than variances in hardness or mechanical strength.
Viscosity matters
One parameter often underestimated when choosing an RTV-1 silicone is viscosity. To the end-user, this might seem like a purely laboratory value, but in reality, viscosity directly affects how the material handles during application.
For N 2189, WACKER provides characteristics typical of a non-sag material. The product maintains solid stability after being laid down. N 2034, on the other hand, is a low-viscosity material engineered to self-level.
Before selecting a silicone, you must answer one core question: Do we want the material to stay exactly where it was applied, or do we want it to flow and level the surface automatically? This single question often narrows down the choice faster than analyzing the fire resistance class alone.
N 2189 for FIPG sealing
An excellent use case for N 2189 is the creation of Formed-In-Place Gaskets (FIPG). In this process, the material is applied directly to the surface of the component; after assembly or curing, it forms a customized flexible seal.
In these applications, the non-sag property is critical. The material must not shift positions between application and the next stage of the assembly process. N 2189 combines this structural stability with mineral oil resistance, thermal resilience, and a UL 94 V-0 classification. WACKER also notes its ability to achieve strong primerless adhesion, especially to die-cast magnesium.
Therefore, N 2189 is an ideal solution when the seal must be flexible, durable, and highly resistant to harsh operating conditions all at once.
N 2034 – When self-leveling is an advantage
For N 2034, the primary selling point is its self-leveling capability. The material naturally spreads across the surface, which is highly beneficial in applications where achieving a uniform, flat layer without manual tooling is necessary.
N 2034 is an excellent choice for technical applications where the method of surface coverage is just as important as the sealing function itself. WACKER highlights its use as a ready-to-use, low-viscosity, self-leveling, and flame-retardant silicone.
This is especially critical in mass production, where the material's physical behavior dictates process repeatability. A product that autonomously flows into a specific shape can eliminate the need for secondary manual spreading steps.
Operating temperature – Another critical factor
While both products were designed for technical applications, their declared operating temperature ranges are not identical. WACKER specifies a range from -45°C to +200°C for N 2189, whereas the recommended range for N 2034 is -45°C to +180°C.
A 20°C difference may seem minor, but in industrial settings, it can make or break an application. If a component is going to operate near its upper temperature threshold, engineers must account for the actual long-term operating temperature, not just brief thermal spikes.
Under high-heat conditions, N 2189 is the more robust candidate, particularly when mineral oil resistance is also required.
Oil resistance – The advantage of N 2189
Another key differentiator of N 2189 is its resistance to mineral oils, which WACKER explicitly lists among the product's primary properties.
This is critical in automotive and heavy machinery applications, where the seal may come into direct contact with oil or operate in an environment saturated with oil vapors and residues. When selecting a technical silicone, verifying the operating temperature isn't enough—the chemical environment the cured material will face must also be factored in.
Which silicone to choose?
If material stability post-application is your top priority, ELASTOSIL® N 2189 is the clear choice. Its non-sag properties allow the bead to hold its shape perfectly, and its combination of mineral oil resistance, an operating temperature up to +200°C, and a UL 94 V-0 rating makes it exceptionally reliable for demanding technical environments.
If, however, you need the material to flow easily and create an even coating, ELASTOSIL® N 2034 is the right tool for the job. Its low viscosity and self-leveling properties ensure a smooth, uniform layer while still maintaining the rigorous safety standards of a UL 94 V-0 rating.
In short: Choose N 2189 when you need a stable, non-migrating sealant with high technical resistance. Choose N 2034 when you want to leverage the material's ability to naturally spread and level itself across a surface.
UL 94 V-0 is just the beginning
Comparing N 2189 and N 2034 highlights a golden rule when selecting professional technical silicones: never choose a material based on a single parameter.
A UL 94 V-0 rating is a vital prerequisite, but a product's true suitability can only be evaluated when that rating is combined with its viscosity, rheology, hardness, adhesion profile, chemical resistance, operating temperature, and application method.
While both ELASTOSIL® N 2189 and N 2034 offer the exact same flammability rating, they have been optimized for entirely different physical behaviors. Because of this, asking "which one is better?" is the wrong approach. The correct question is: Which one better meets the manufacturing and physical demands of this specific application?
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