10 Things to Consider When Buying Custom Silicone Gaskets

The process of choosing a material for your custom gasket is intricately woven into your design process. Material informs design as much as design informs material, so deciding on both of these items together will help you land on just the right material for your needs.

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We’ve found, in our years of helping customers choose the perfect material for their custom gasket, that there are 10 very important questions you should be asking yourself when choosing a material that will help you get it right the first time:

1. Will the gasket be used in an indoor or outdoor application?
2. What temperature range must your gasket operate in?
3. What does your industry require?
4. How hard or soft does your gasket material need to be?
5. Do you need a three-dimensional or flat gasket?
6. How will your custom gasket be assembled?
7. What will your housing be made out of?
8. What chemicals will the gasket be exposed to?
9. How small is the gasket?
10. Is outgassing a concern?

Please keep in mind this article is meant to provide general guidance, and there are many materials with different properties and specifications to choose from within each general material category. Narrowing down to your final material is something best done with the help of an expert. This guide is designed to help you start the process of material selection, before diving into the nitty gritty details.

Will the gasket be used in an indoor or outdoor application?

Usually, the first question to ask is where your custom gasket will be used. Indoor applications will have an entirely different starting set of materials to consider than outdoor applications.

If your gasket will be used outdoors, you’ll likely need a larger supported temperature range, a material that can withstand the elements, and has resistance to ozone or sunlight. A good general rule of thumb is the more a gasket can withstand, the higher the material cost.

Indoor applications can generally get away with lower cost materials than outdoor applications.

Some materials that are a good fit for outdoor applications include:

• Most solid gasket materials
• Silicone or EPDM sponge materials
• Some silicone and polyurethane foams
• Silicone Form-in-Place (FIP) materials

Another consideration that falls into this category is if the gasket will be enclosed or exposed when used in an outdoor environment. If it will be enclosed, and there will be protection from chemicals and ozone, you will obviously have a larger variety of materials that may fit your needs.

What temperature range must your gasket operate in?

This question tends to work hand in hand with the previous one. Generally speaking, outdoor applications will require a higher range of temperatures to which the gasket must be resistant.

Start by narrowing down the highest and lowest temperatures your gasket will be subject to and layout the full range. You’ll want to find a material that can operate across the entire range, rather than just ideal conditions. As you might expect, the larger the range of temperatures supported by a material, the higher the cost.

Selecting the right material in this case is a balancing act between making sure your gasket can operate across exactly the range it needs while reducing the material cost.

Some materials that are resistant to extreme temperatures include:

• Most solid gasket materials, Silicone and Fluoroeleastomer(FKM)
• Some silicone sponge materials
• Silicone FIP materials

What does your industry require?

Depending upon your industry, there may be very specific material requirements you need to be aware of. Some examples include:

• Materials used in military applications will have to meet MIL SPEC requirements
• Materials used in medical applications may require the use of FDA, CFR 177., USP Class VI compliant materials that are either non-toxic or have skin compatibility
• Food handling or agricultural applications may require FDA compatible materials should food or liquid come into contact with your custom gasket
• Rail and mass transit applications often require specific UL or flame ratings

Make sure you’ve considered all of the requirements that apply to your application and be sure you select a material that meets those requirements before getting too deep into the design process.

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How hard or soft does your gasket material need to be?

Balancing the hardness of your material with the lifespan will be the biggest challenge in this instance. In general, the softer a material, the shorter the expected lifespan will be. 

Softer gaskets are important in instances where there are larger gaps, uneven gaps, or you are concerned with damaging the materials the gasket is touching. Harder gaskets are best for instances where compression forces will be high, and a longer lifespan is important.

Durometer is the measurement of hardness in a material and provides a quantitative indication of how resistant said material is to permanent deformation or indentation. Make sure you’ve considered the durometer range needed for your design and find a material that meets those specifications.

Compression force deflection is another measurement that will be important in material hardness. It is defined as the force required to reduce material thickness by 25%. Softer materials require on the order of 2 psi to reduce thickness by 25% whereas harder materials require upwards of 17 psi. 

Some materials that are good for softer gaskets include:

• Sponge materials
• Foam materials

Some materials that are good for harder gaskets include:

• Solid materials
• FIP materials

Do you need a three-dimensional or flat gasket?

If your gasket needs to be three-dimensional you’ll be looking at custom molded silicone or rubber to meet your needs.

Flat gaskets on the other hand have a wide variety of materials you can choose from depending upon your answers to some of the other questions in this list.

How will your custom gasket be assembled?

An important consideration that is often overlooked in the design process is how the assembly process will need to work. It is very easy to design in a vacuum and ultimately lose sight of factors that may make it easier or harder to add your gasket to your assembly process in the long term.

Some of the more obvious considerations that usually are considered in design are the requirement of adhesive backing and the compression forces being applied to the gasket. Both of these will limit your available choices of gasket materials depending upon your needs.

Some of the considerations that are often overlooked include:

• How long will the assembly process take and/or cost? Often smaller, thinner gaskets are hard to work within the assembly and increase production time. In this case, FIP materials may be a better choice to improve production time and reduce labor costs.

• How hard do you want the assembly to be? In general, the softer the gasket material, the easier assembly will be in the end, as lower compression force will be required to get it into place.

• Will everything be assembled right away? Sometimes assembly processes are broken into smaller chunks, but choosing to use a material like thermal paste adds the requirement that everything must be immediately assembled before the paste dries.

Just make sure you’ve considered your assembly process before ultimately deciding upon the best fit material to ensure you don’t have to come back and redesign later.

What will your housing be made out of?

While you are obviously considering the material of your gasket itself, it is also important to keep in mind the materials for your housing.

Knowing how hard the housing materials are will help you decide on a gasket material that will work well in the environment you are placing it. For instance, in cases where a plastic housing is used, you have to be careful to select a gasket material (e.g. a sponge material) that won’t cause cracking at your compression stops.

What chemicals will the gasket be exposed to?

You will want to ensure you are aware of the range of chemicals your gasket may come into contact with. This will probably be one of the most important considerations that will significantly narrow your choices should you expect any harsh chemicals to be present.

Some custom gasket materials that are resistant to a variety of chemicals include:

• Fluorosilicone
• Neoprene
• Nitrile
• Fluoroelastomer

How small is the gasket?

The size of your gasket will help you determine if it is the best fit for form-in-place (FIP) dispensing or not. Narrow, small or flimsy gaskets are often much easier to dispense via FIP than trying to cut and assemble them by hand.

Is outgassing a concern?

This consideration is typically only a real problem in custom gaskets used in hard drives, where outgassing may cause contamination of the drive. In this case, you’ll need to use a material other than silicone to get rid of outgassing.

The Bottom Line

You’re on page 5 of 32 material selection pages… Getting sleepy yet? Rather than continue staring at nearly identical rolls of material, sit back and relax as we discuss whether silicone is the right choice for your application.  

Silicone gaskets offer a wide range of heat-resistance and durability benefits, making them a popular choice for gasket manufacturing. 

As a converter, Strouse regularly builds custom gaskets for our clients. We’re familiar with silicone’s material behavior compared to other gasketing materials, so today, we’ll explain its uses.

Read on to learn about the benefits and uses of silicone gaskets, plus what to consider when choosing a material for your gasket design. 

What is a Silicone Gasket?

If you’re looking for multi-temperature range, high-performance mechanical seals with high resilience and durability, you should consider using silicone gaskets. 

Silicone gaskets can withstand high and low temperatures, making them a highly versatile material. Use them when you need a material with high-temperature resistance, a low compression set, and good electrical insulation. 

TYPES OF GASKETS

The type of material in your gasket depends on its intended use. For example, if you’re dealing with a rigid object, you need a gasket that fits the set shape. Doors and moving structures need something more flexible.

Before you design a gasket, consider your needs, including temperature, pressure, corrosion resistance, availability, and cost.

Gaskets must be solid so they don’t allow materials to pass through, and some need to handle energy discharge. You can have many different types of gaskets, including:

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• Pipe gaskets
• Gasketing tape or adhesive
• Gasketing foam

And many different materials, including silicone, neoprene, EPDM, Teflon, Gore-Tex, and graphite gaskets.

What Are the Uses of Silicone Gaskets?

Because of their versatility, silicone gaskets are used in many different industries.

AEROSPACE

Silicone gaskets resist extreme temperatures, UV light, ozone, and chemicals. Because they can handle extreme weather and temperatures without wearing down, they’re often the right fit for airplanes, space shuttles, and similar vehicles. 

TRANSPORTATION

Silicone gaskets are stable and durable, maintaining their resilience and strength even in extreme conditions. Because they can handle unnecessary stress without issues, they are great for personal, commercial, or industrial vehicles. In addition, they reduce vibrations, provide high-quality radiator seals, and are otherwise used for mass transit systems like buses and trains.

COMMERCIAL APPLICATIONS

In the construction industry, silicone gaskets seal HVAC systems and windows or doors. You can also use them in engine gaskets to vent ducts. 

Other uses of silicone gaskets include sealing food processing machinery and industrial ovens in the food industry. The medical industry uses them for medical equipment like healthcare devices and pharmaceuticals. 

What Are the Benefits of Silicone Gaskets?

Before we get into the different types of silicone gaskets, it’s worth considering the properties that differentiate them from other gasketing materials.

There are thousands of materials to make gaskets, but silicone stands out thanks to the benefits that allow it to be used in indoor and outdoor applications. 

1. ABILITY TO WITHSTAND HIGH AND LOW TEMPERATURES

Silicone gaskets can withstand temperatures up to 392 degrees Fahrenheit continuously, which makes them great for many industrial applications. It can be exposed to high heat levels without degrading or wearing out. 

Silicone seals can also withstand heat up to 428 degrees Fahrenheit intermittently and withstand extremely cold temperatures, remaining flexible at as low as -94 degrees Fahrenheit.

2. EXCELLENT INSULATION

Silicone gaskets have conductive capabilities that make them excellent insulators of electricity. Blending silicone with nickel-graphite or silver-plated aluminum particles can shield electromagnetic interference (EMI).

Silicones are found in most high-voltage insulators and other electrical components. Different chemical reactions can cross-link them, making them non-reactive at high temperatures. The electrical industry relies on these non-reactive materials. Silicone can also be blended with semi-conductive carbon to prevent electromagnetic discharge.

3. HIGHLY DURABLE

Silicone gaskets are highly durable and resistant to UV light, ozone, and extreme weather conditions, making them ideal for outdoor gasketing. 

Plus, silicone's tensile strength and durability make the gaskets highly economical, as it is a reliable and stable material. You can use these gaskets for a long time without them showing wear, and once installed, they don’t require much maintenance.

4. FDA APPROVED

Because silicone gaskets are FDA-approved, they can be used in medical equipment, health care instruments, and food processing plants. They can also be mixed with other FDA-approved materials for high tear strength.

Unlike asbestos gaskets, silicone gaskets are also physiologically inert (not toxic or harmful to people). Their high tear strength and inertness make silicone gaskets useful for healthcare, food processing, medical diagnostic equipment, and pharmaceuticals.

5. COMPRESSION SET RELIANCE

Compression set reliance means that silicone gaskets function well under pressure by returning to their original thickness even after being compressed for long periods. 

Silicone gaskets are a smart choice for a lower compression set. A compression of 100% means the material will never return to its original thickness. Lower compression set reliance materials ensure the material doesn’t get deformed in certain temperatures.

Matching the compression set reliance of your material to your intended use is essential. If the gasket material deforms, the seal will fail, leading to leaks and contaminations.

6. FLAME RETARDANT

Silicone gaskets have low flammability levels, making them ideal for industries that generate excessive heat. They can also be used in telecommunications equipment and mass transit systems. 

Silicone gaskets meet Underwriters Laboratories (UL) testing requirements for fire safety and flame resistance, meaning they can achieve UL94V0, UL94V1, and UL94HF1 flammability standards.

7. WATER-REPELLING MATERIAL

Silicone gasket material is water-repelling, repelling liquids, resisting moisture, and maintaining a watertight seal. This sealing ability is essential for industries dealing with moisture or water and is great for outdoor use in wet weather conditions. 

What Are the Types of Silicone Gaskets?

Silicone gaskets can come in sheets or rolls of different thicknesses. Depending on your needs, you can also use solid, sponge, or foam silicones.

TYPE #1: SOLID SILICONE GASKETS

Solid silicone gaskets are not always soft but rather tightly packed and more rigid than sponge silicone. If you need a seal rating of IP67 or higher, you’ll want to choose solid silicones. 

Solid silicones can offer exceptional sealing capabilities, but remember that they’re challenging to compress because of their hardness and require 15 to 20% compression.

TYPE #2: SPONGE SILICONE GASKETS

Sponge silicone gaskets offer more cushioning and padding. They can be open-cell or closed-cell. Open-cell silicones contain pockets that allow water, air, and chemicals to pass unless the gasket is compressed.

Closed-cell silicones have pockets filled with nitrogen to prevent water, air, or other chemicals from passing through, even at low compression. They will need at least 50% compression. Sponge silicone gaskets have a higher temperature threshold of 500 degrees Fahrenheit.

TYPE #3: FOAM SILICONE GASKETS

Foam silicone gaskets can be soft, medium, firm, or extra-firm and offer different compression levels. Like sponge silicone gaskets, foam silicone gaskets need at least 50% compression. They can be open-cell, closed-cell, or a mixture of both, and their temperature threshold is 400 degrees Fahrenheit.

TYPE #4: DIE CUT SILICONE GASKETS

Die cut silicone gaskets are a common type of gasket, built using custom machine tools to create unique parts. 

If you’re using your design with custom sizes and thicknesses, die cut silicone gaskets could be a good option. They’re often a more economical option for large volumes, because thousands of die cut gaskets can be produced per hour. 

TYPE #5: MOLDED SILICONE GASKETS

Molded silicone gaskets provide a higher-performance seal than die-cut silicone gaskets. However, this might come at a higher upfront cost, even though both are good for high-volume production. 

TYPE #6: CONDUCTIVE SILICONE GASKETS

Conductive silicone gaskets are made up of a mix of high-quality silicone and conductive particles. They are filled with conductive materials like nickel, carbon, and silver-plated nickel and are used for electronic equipment.

TYPE #7: FDA (FOOD GRADE) SILICONE GASKETS

FDA-approved silicone gaskets are generally used in the food processing industry. They are odorless, tasteless, and fungus-resistant. They also can handle extreme cold and heat, making them ideal for places with food around, like dough or cake mixers.

TYPE #8: FLUOROSILICONE GASKETS

Unfortunately, silicone isn’t ideal for oil or petroleum-based chemicals. Fluorosilicone, or fluorinated silicone rubber, is similar to silicone, except it can withstand extreme temperatures and resist fuels, oils, and other petroleum-based chemicals. 

Silicone Gaskets vs Rubber Gaskets

Choosing between a silicone and a rubber gasket will depend on your goals. Silicone gaskets can be more efficient and perform better than rubber gaskets, especially in extremely high temperatures.

Natural rubber can work well in temperatures from -58 degrees to 176 degrees Fahrenheit intermittently, whereas silicone can handle more extreme temperatures, from -94 degrees to 426 degrees intermittently. Natural rubber starts to wear down at 176 degrees and melts by 248 degrees.

The cost of rubber materials like SBR can make them more appealing than silicone in pricing. However, rubber is not used with ozone, strong acids, fats, oils, and grease. Silicone, on the other hand, can be used with these materials. You can use silicone gaskets in UV and extreme weather conditions for outdoor applications.

Ultimately, you’ll want to consider your design and application before finalizing your product material, which leads us to… 

Choosing the Right Gasket Material For Your Solution 

Now that you know more about silicone gaskets, you’re ready to pick out a gasket adhesive that suits your needs. Moreover, given the complexity of material behavior, you’ll want more to go off of than simply matching the numbers on a data sheet.  

Before you finalize your design, you might want to test the material within your application. Requesting a design sample will allow you to see if silicone really is the best choice for your gasket design. 

It’s one thing to build the perfect gasket once, but how can you consistently manufacture your part to reduce the chances of product failure? 

We’re here to help you through your product development process. Reach out to ask questions or request a sample. Lastly, please visit our Learning Center for additional resources.

Originally published: February 24,

Contact us to discuss your requirements of Custom Silicone Gaskets. Our experienced sales team can help you identify the options that best suit your needs.