What Is a Gasket? Everything You Need to Know

When was the last time you saw a gasket?

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Gaskets are everywhere. They’re at work, in your car, and even in your phone. A gasket is a common term for any seal or grommet that holds two things together. 

You can make gaskets from rubber, plastic, metal, and other materials depending on the purpose for which you’re building. At Strouse, we’ve worked with hundreds of different gasketing materials to make custom products. 

As you'll learn, there's more to gaskets than a seal preventing a leak. But before you blow a gasket trying to determine the difference between each type, let us investigate and share what you’ll need for your own project.

Definition of a Gasket

A gasket, also known as an O-ring or washer, seals the gap between two surfaces. These items are usually made of rubber and are available in different sizes and shapes depending on their purpose.

Strouse tip: The material selection is one of the most important parts of creating the right gasket.

The most common type of gasket is flat with a circular cross-section. The diameter of cylindrical gaskets is typically round and ranges from 1/4 inch to 3 inches. It appears as a long tube with a different diameter at each end.

Gaskets come in many variations, as we'll see later. In this article, we will move into more detail about each of them. Let’s start by looking at the difference between a gasket and a seal.

How Are Gaskets Tested?

Gaskets undergo trials such as the hot compression test as part of the evaluation process. This test determines the heat it can withstand without causing damage or failure in the material.

During the compression test, It becomes essential to check for any leaks in the sealant and look for any other problems, such as pinholes or cracks with the sealant. For the final stage in the manufacturing process, technicians examine the product, checking it for all aspects before it leaves the facility.

Gasket or Seal?

Considering that "seal" can be used as a noun and a verb, many people confuse gaskets with seals and use both terms interchangeably. Yet, seals serve a similar purpose, with one significant difference.

Gaskets and seals form barriers between two objects to keep them from leaking. However, seals protect at least two moving parts (whether only one of the parts moves or both) and are commonly composed of flat and round washers, like those found in faucets.

Two static seals make up a gasket. These seals allow two static, non-moving parts to be locked together.

Because of this, gaskets are often molded to fit a specific static application. Or, they might be malleable enough to fit into a given position and keep it there as long as they don't move against each other.

Properties of a Gasket

Your ideal gasket should not only seal, but also protect against corrosion. It should resist abrasion, vibration, impact, and possibly extreme temperature.

The ideal material will have good flexibility, low density, and high tensile strength. Many of these materials share a resistance to chemicals and possess both internal pressure and durability. 

That said, strength is the most crucial feature of any gasket application. Your gaskets must have enough strength to withstand pressure without deforming under normal conditions so they can serve their primary function of creating a tight seal over a long period of time.

When are Gaskets Used?

Gaskets occur in many industrial applications, including Food Processing, Petrochemical, Plumbing, Machinery, and Gas. The easiest way to summarize these is to think, "If it needs sealing and doesn't move, chances are it's using a gasket."

Examples around the home include gaskets in water faucets and around windows. Appliances, such as refrigerators, have them to keep cold air inside, and examples in the workplace involve them in machinery, pipes, valves, and pumps.

Most people think of head gaskets as stainless steel or the metal ones used in cars. But as you’ve already seen, there’s a much larger range of potential uses.

Many gaskets are inexplicably disguised under a different name, like washers or o-rings, yet they all serve vital functions across many applications. 

8 Types of Gaskets and Materials

There are many kinds of gaskets used in all kinds of settings. Each material is preferential depending on the most important properties required.

Gaskets come in various materials, including metal, plastic, silicone, and glass fiber-reinforced polymers. But they all must fit snugly against their mating surface so there's no air leakage around them.

With this information, let's look at each type of gasket. Further, we'll look at their properties and how they apply in the everyday setting:

1. RUBBER 

The synthetic rubber gasket is one of the oldest forms of sealing technology. Charles Goodyear first developed rubber gaskets around 1844 for his invention of vulcanized rubber, although they can be made from either natural or synthetic materials.

We go into greater detail about these below, as each differs slightly. You can find rubber gaskets in a wide variety of applications, including:

Automotive

The most common application of rubber gaskets is automotive use, often found on doors and trunk lids to seal out moisture and other contaminants. Also, many vehicles have seals between their engine block and cylinder head which need an effective seal against water intrusion.

Rubber gasket manufacturers are looking for ways to improve the performance of their products by developing new formulations that provide better sealing characteristics at a lower cost than previous generations of materials, helping bring the cost of automotive parts down as a result.

Industrial

Industrial uses include sealing equipment such as pumps, valves, conveyors, etc., where there's constant exposure to harsh chemicals and abrasive particles. These environments also create high heat loads, so these components must remain sealed tight.

Medical

Medical devices like catheters, tubing, IV bags, etc. must maintain a good seal to prevent contamination and infection. Hospital dehumidifiers rely greatly on airtight seals to keep the indoor environment clean and dry.

Food & Beverage

Gaskets are often used in food processing plants to ensure proper sanitation and safety. Food processors use them to protect raw meat and poultry from cross-contamination with other foods during preparation. The same goes for beverage bottlers who use gaskets to help prevent leaks when filling bottles with carbonated beverages.

2. SILICONE 

Dr. William H. Dow Corning Company invented the silicone gasket in 1953. This product is often known as "silicone" because it contains silicon atoms within the molecule structure.

Silicones are durable and resistant to chemicals such as acids, alkalis, oils, solvents, water, heat, radiation, and ozone. This makes them an ideal choice for food processing applications.

Since its introduction into clinical practice, silicone rubber is also commonly found in medical devices. 

Silicone rubbers have several desirable properties that make them useful in many industrial processes. These include high-temperature resistance, low compression set, and good electrical insulating characteristics. They also possess excellent chemical inertness, biocompatibility, and an ability to be easily bonded or vulcanized with other materials.

3. EPDM 

EDPM is another form of elastomer, which stands for ethylene propylene diene monomers. EPDM is similar to silicone, except it contains additional ingredients like fillers, plasticizers, stabilizers, antioxidants, flame retardants, etc. These additives make up about 10% of the total weight of the polymer.

EPDM rubber gaskets have high resistance against heat and chemicals and good flexibility. The material can be used in many automotive parts, industrial products, medical devices, toys, footwear, construction, and electronics.

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4. NEOPRENE 

Neoprene gaskets comprise a thermoplastic elastomer based on polychloroprene. Neoprenes are widely used in medical devices due to their ability to maintain shape while stretched over long periods. 

Because neoprenes do not stretch back out when released, they are often used in products with continuous motion. In addition, neoprene materials are highly elastic and flexible, so they can easily conform to irregular surfaces. 

The most common method for manufacturing neoprene involves using an extruder that heats and melts the polymer into its final form. The molten material then passes through a die orifice that shapes it into the desired product.

Until now, we've mainly discussed rubber and silicone gaskets, but some materials and designs cross over, so you might find multiple types in the same setting. 

5. FOAM 

A foam gasket is composed of two layers of closed-cell urethane foam bonded together using adhesive tape. Foams are generally more expensive than rubbers but generally less expensive than silicones.

However, foams offer superior thermal insulation and sound absorption qualities in a variety of applications.

Thermal Insulation

Thermal insulation reduces the amount of heat that passes through an object by reducing its ability to transfer energy from one surface to another.

The most common application for insulating materials is building construction, where it helps keep warm air inside buildings during cold weather or cool air outside during hot summer days.

Sound Absorption

Sound waves travel at different speeds depending on whether they travel through solid or liquid objects. This means that if you want your home to have quiet rooms, you need to reduce the sound within those spaces.

One way to do this is to place absorbent materials between the source of noise and the room's occupants. A foam gasket will help dampen sounds before they reach people's ears.

6. O-RING 

An O-ring gasket consists of many rings of metal with an inner diameter smaller than the outer diameter of the sealed object. When compressed between the objects, the ring expands outward until it contacts both sides of the gap. Once contact occurs, the force exerted by the expanding ring causes the opposing surface to deform inward toward the center of the ring, creating a seal.

Using such seals in various applications was popular for many years and is still popular today. For example, o-rings help sealing shafts or other rotating parts that need maintenance to prevent leakage.

Here, the o-ring provides a barrier against fluid flow along the length of the shaft, while allowing rotation thereof. The o-ring also prevents contaminants from entering the housing interior through which the shaft extends.

7. PTFE 

PTFE is a fluoropolymer material with many uses, but it works great as a gasket material. PTFE has excellent chemical resistance and is a low friction coefficient. They also have high-temperature stability, good electrical properties, and outstanding dielectric strength.

It's also nonporous and inert, meaning it does not react with other substances. Thus, PTFE gaskets are most often found in food processing equipment, pharmaceutical manufacturing processes, semiconductor fabrication facilities, and nuclear power plants. They are also used in medical devices because they do not support bacterial growth.

8. EMI SHIELDING

EMI shielding gaskets are made from metal alloys and other flexible dampening materials. They fit on the inside or outside of electronic devices to prevent outside signal interference from damaging the inner mechanisms and causing malfunctions. 

While there are more than eight different types of gaskets, hopefully seeing some of your options has given you a clearer picture of capabilities. 

How Can I Choose a Gasket?

Your gasket choice depends entirely on its function, which is why you’ll want to find the right gasket material for your next project.

Once you’ve identified the type of material you’ll be using, you can perfect your gasket design and start figuring out how to create it.

Originally published: July 14, 2021