Rubber Gaskets and Rubber Grommets

Jun 02, 2026

From time to time, we see some confusion between gaskets and grommets. Ask for one when you need the other though, and you’re likely to encounter problems, so this blog should clear things up.

What Are Rubber Grommets?

Usually circular, rubber grommets plug holes in walls and enclosures. Some are solid and intended to stop anything passing through. Most though have a central hole that lets a cable or pipe pass through.

In this kind of application, the grommet stops the cable or pipe from coming into contact with the wall. It also fills the space to prevent fluid or particles passing from one side to the other.

A related use for grommets is to absorb vibration. This is especially important with pipes where fluid movement could create annoying resonances in the enclosure wall.

What are Rubber Gaskets?

Rubber Gaskets seal joints between two surfaces. Pipe flanges, where two sections of pipe are joined, are a prime example. Lids, covers and doors are related applications where the gasket seals the gap between opening element and surround.

Important properties of gasket materials are:

  • Soft enough to conform to the surfaces being sealed – ensures gaps are filled
  • Compressibility and resilience or elastic recovery – to thin down and expand as the gap between the surfaces varies
  • Strength – to resist the forces imposed by internal pressure
  • Flexibility and strength at working temperature
  • Chemical compatibility – so the material isn’t attacked and degraded by the fluid it’s sealing

Materials for Rubber Grommets and Gaskets

“Rubber” is a generic term used for a wide range of elastomeric materials. Natural rubber is made from the latex sap of the rubber tree. Today, it has largely been supplanted by synthetic rubbers made from polymers.

Two synthetic rubbers used for grommets and gaskets are nitrile butadiene rubber(NBR) and styrene butadiene rubber(SBR). SBR is flexible and inexpensive, while NBR offers superior resistance to oils and fuels.

Contact Hennig for Expert Advice

At Hennig we help customers solve their gasket challenges. Contact us for advice on materials and help with your next sealing application.

Rubber Gaskets
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Cutting Silicone Gasket Material

May 05, 2026

Silicone sheet is an excellent material for gaskets. However, the characteristics that make it good for sealing joints and surfaces also make it difficult to produce smooth edges.

Why Use Silicone for Gaskets?

Silicone is soft, compressible, and has good elastic recovery, but the most important characteristic is its temperature range. Silicone remains flexible at temperatures from -94 to +392°F, which is wider than almost all other elastomeric materials.

Silicone sheet is produced in many colors and formulations, including FDA-approved grades. Overall, chemical resistance is good, although it is vulnerable to hydrocarbons like oils and fuel.

The Challenge of Cutting Silicone

It’s hard to get a good quality edge or to cut an exact shape. Silicone tears, moves, compresses and springs back, leaving ragged edges that look unattractive and could affect fluid flow and gasket function.

Best Ways of Cutting Silicone Gasket Material

We’ve been producing gaskets for many years and we’re familiar with all types of material. Our preferred ways of cutting silicone are:

  • Water jet: Fast, results in smooth edges, and material utilization is good, thanks to the narrow kerf. It requires a CNC program, which we can generate from customers’ CAD files or by reverse engineering an existing gasket.
  • Die cutting:The process of using a sharp-edged steel rule bent to the shape of the gasket and embedded in a board. It’s fast, accurate, and achieves excellent edge quality, but if we don’t have a tool available making one will impose a short delay.
  • Flash cutting: Uses an oscillating blade to cut through sheet material. Edge quality is good although the process isn’t quite as versatile as water jet for very complex geometries.
  • Hand cutting: Sometimes used to avoid setup time on single piece orders. Not as accurate as using automated equipment but with a skilled cutter the results can be very good.

Custom Gaskets Made to Order

We produce gaskets for all kinds of applications and in many different materials. Silicone makes great gaskets but can be hard to cut without experience and the right equipment. We have both. Contact us to learn more.

Silicone Gaskets
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What are Die Cut Gaskets?

Apr 07, 2026

Thin, non-metallic gaskets are often produced by die cutting. It’s an economical process that’s especially useful for making gasket kits. However, as with every manufacturing process, there are some limitations. This blog will describe what die cutting involves, what it’s capable of, and its relevance to kits.

Steel Rule Die Cutting

Die cutting involves pressing a sharp steel blade down into the material. This blade is bent into the profile of the gasket needed and secured in a plywood or phenolic board. The board is then mounted to the upper surface of a press, which pushes it into sheet material placed underneath.

Die Cutting Process Capabilities

Maximum gasket size and thickness are determined by the press. Our 75 ton presses can die cut parts up to 36” x 62” and up to 1” thick. (Thickness depends on the material being cut and the profile length.)

Cutting dies are inexpensive and can be nested to improve material utilization. Controlling the depth of cut enables “kiss” cutting, where the blade only goes part way through the material, or stops at the backing layer.

Advantages of Die Cutting

A major strength of this process is the ability to make gasket kits. This is done by nesting multiple blades on a board, which ensures the required quantities of each gasket are made.

In addition, by kiss cutting the sheet, the gasket kit is kept together. This simplifies handling and storage.

Die Cutting Limitations

This is a process that needs part-specific special tooling. We hold a substantial inventory of dies, but a new tool will be needed for a custom shape. In addition, the press needs a limited amount of setup before running an order.

Together, these points mean die cutting is best for medium quantity orders. For small quantities we recommend flash or waterjet cutting instead.

Our Custom Die Cutting Services

If we don’t have a die for your particular gasket shape we will be happy to make one. To ensure accuracy, we can reverse engineer existing gaskets to produce a custom die for your needs. Contact us for a quote.

FAQs
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Introducing Filled Grades of PTFE Material

Mar 04, 2026

PTFE is known for a wide working temperature range and resistance to a broad spectrum of chemicals. It’s also very soft, unless reinforced with a filler. Fillers increase strength and creep resistance, but change where and how the material can be used. This blog reviews the reasons for choosing PTFE and discusses the main filler materials and their benefits.

PTFE Characteristics

Virgin PTFE withstands temperatures as high as 500°F (260°C) and remains flexible down to -430°F (-257°C). It’s also chemically inert, resisting attack by almost all acids and alkalies other than fluorine or nitric acid. In some applications its low friction is an asset, but it does tend to wear.

However, very low tensile strength (2,900 – 5,000 psi) and minimal elastic recovery, limit applications to those where creep won’t be a problem. These tend to be in the food industry where the advantages – it doesn’t impart any taint and is not hazardous if ingested – outweigh the design constraints it imposes.

Adding Fillers to Virgin PTFE Material

Tensile strength is raised by adding fillers. These reduce its tendency to creep and widen the range of potential applications. However, most filled grades lose their FDA “food grade” rating.

The properties of filled grades are strongly influenced by the characteristics of the filler material. Here’s an overview of those most widely used.

  • Glass: Chemically-inert with much less propensity to creep. Can be abrasive.
  • Carbon: Has increased wear resistance and higher thermal conductivity. Provides enough electrical conductivity to dissipate static.
  • Graphite: Lowers friction, but unlike carbon, does not increase wear-resistance.
  • Molybdenum Disulfide (MoS2): Reduces friction and increases wear-resistance. Often used in PTFE dynamic seals.
  • Bronze: Provides thermal and electrical conductivity and increases wear-resistance, but lowers chemical resistance.

Get Help When Selecting PTFE Material

When a gasket application needs excellent chemical resistance, PTFE often tops the candidate list. It’s important to consider though, that virgin PTFE material is soft and easily deformed. This can be addressed by using one of the filled grades.

Fillings alter properties like friction and wear-resistance. This should be considered during the material selection process. Specialists at Hennig Gasket & Seals are always happy to help.

PTFE Gaskets
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Materials for Washer Gaskets

Feb 03, 2026

People don’t usually consider washers a type of gasket, but depending on how they’re being used, that’s exactly what they might be. This blog discusses what washer gaskets do and what to consider when selecting material for them.

Washers for Sealing

A washer is a ring of material under the head of a bolt or under a nut. In fastening applications it’s job is to spread the load being applied. A washer gasket is a ring of gasket material placed under a bolt head or nut. Gasket material isn’t a good load spreader because it’s soft and compressible, but it can have three other functions:

  • Seal against fluids
  • Dampen transmission of noise and vibration
  • Prevent galvanic corrosion

Another way washers, felt washers specifically, are used is to lubricate a rod or shaft passing through the washer. This works because felt washers are very good at retaining oil.

Washer Gasket Material Options

Like any gasket, a washer gasket has to take up deformations in the surfaces it’s sealing. This requires compressibility. Recovery, or resistance to compression set, may be another useful property if the bolt is likely to get hot and expand.

Other selection criteria relate to the media being sealed and the environment the washer gasket will go into. This means looking at characteristics like tolerance to oils, acids and alkalies, and UV and ozone. Then consider temperature, both of the media and the environment.

For dampening applications the vibration-attenuating properties of the material are what matter most. This is where a knowledgeable supplier can be a big help.

Galvanic corrosion occurs when metals with different electrolytic compatibilities come into contact in the presence of moisture. For this type of application the washer gasket’s job is to be an insulator between the two metals.

Depending on the application and the temperature range needed, good material choices can be:

  • PTFE
  • Neoprene
  • EPDM
  • Silicone
  • NBR
  • SBR

Advice From Hennig Gasket & Seals

With many different materials to choose from, deciding which is best for an application can be quite daunting. A risk-free approach is to consult the specialists at Hennig. Contact us today.

Flange Gaskets
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Advantages of Silicone for Customer Gaskets

Jan 07, 2026

When choosing material for a custom gasket application, going through the temperature, environment, media and pressure criteria may leave you with a few options. Silicone probably won’t be the cheapest, but it could be the most cost-effective. Here’s when and why to consider custom silicone gaskets.

Excellent Sealing Properties of Silicone

Silicone remains flexible from -94 to 392°F (and withstands temperatures up to 500°F for short periods). It takes a very low compression set, retaining its ability to seal over hundreds of opening and closing cycles. It’s tensile strength is up to 1,100 psi.

Silicone Material Broad Chemical Compatibility

Silicone repels water and resists attack by ozone and UV light, making it a good gasket material for outdoor applications. Being chemically inert, It resists weak acids, most alkalies and hydraulic fluids and oils. Where it performs less well is in resisting attack by strong acids and solvents.

Available in Multiple Grades and Material Thicknesses

Silicone gasket material is produced in sheet form with thicknesses up to ¼”. (Contact us if you need thicker.) It’s made in a range of formulations with various hardnesses and strengths. Colored silicone is available, as are FDA and medical grades.

For greater compliance in lightly-loaded sealing applications, consider using closed or open cell silicone foam.

Size and Shape Options

Custom gaskets often need very specific or unusual features or dimensions. Ask your custom silicone gasket maker what processes they have and about their size and shape capabilities.

At Hennig Gasket & Seals we use waterjet cutting for especially challenging gaskets. Waterjet yields a very smooth edge and can cut features as small as ¼” diameter. Flash, die and hand cutting are also available, depending on quantity required.

Silicone, For Long-Lasting Gaskets

Besides offering a wide temperature range and good chemical resistance, silicone makes a very durable material. If you have applications where a joint, cover or door will be opened and closed multiple times, silicone will probably continue to seal longer than other materials. This can make it very cost-effective when compared to materials like EPDM, neoprene and nitrile. Contact us to learn more.

Silicone Gaskets
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EPDM vs. Viton Gasket Material

Dec 27, 2025

For a wide temperature range and good chemical resistance, many gasket material buyers think they have to specify Viton®. There are times when this is the right choice, but sometimes it isn’t. For many applications EPDM is a better material. This blog does an EPDM vs Viton comparison so you can decide which to use.

Chemical Comparison

EPDM gasket material and Viton gasket material are both flexible elastomers suitable for sealing gaps and joints in a wide range of applications, but chemically they are quite different. Viton is a tradename for a family of fluoroelastomers that go by the acronym FKM. EPDM, (Ethelyene Propylenen Diene Monomer), is hydrocarbon-based. During manufacture EPDM is cured with either sulfur or peroxide. Peroxide curing raises strength and the upper temperature limit.

Viton was developed by DuPont and is now a Chemours product. Chemically, its main feature is the presence of fluorine. This bonds with carbon to provide excellent resistance to chemical attack.

Property Comparison

  • Temperature range: Viton is flexible from -4 to 410°F. EPDM works from -60 to 225 or 300°F, depending on curing process.
  • Strength: Viton and EPDM are similar with a tensile strength of around 1,000psi. Peroxide-cured EPDM is stronger, up to 3,000psi.
  • Compression set: Both materials perform well.
  • FDA grades of both are available

Chemical Resistance

This is where the two diverge. EPDM resists:

  • UV
  • Oxidation
  • Acids
  • Alkalies
  • Ketones
  • Water and steam

Limitations are hydrocarbons and petroleum fluids, which cause swelling.

Viton resists most chemicals, except ketones, and organic acids. The latter, (substances like acetic, citric and tartaric acids), occur in food and beverage processing.

When to Use

EPDM works well in outdoor applications. It’s often used for weather stripping and dust covers, as well as mounts of various types. Another application is for low pressure boiler gaskets. FDA-grade EPDM is used in food and beverage equipment.

While Viton can be used in food processing, (subject limitations mentioned above), its main use is in fuel-handling equipment like pumps and valves. It’s also used in a lot of chemical processing equipment.

Expert Advice is Available

Specialists at Hennig Gasket and Seals are always happy to discuss gasket material applications. Contact us and let’s talk!

Gasket Material
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Understand What SBR Rubber Means

Feb 15, 2025

If you’re looking for a flexible, inexpensive, abrasion-resistant material, SBR rubber should be on your list of candidates. In this blog we’ll explain what it is, when you might use it, and what “SBR” means.

SBR Chemistry

SBR is an acronym for Styrene Butadiene Rubber. It’s a hydrocarbon-based synthetic material developed in the 1940s as a response to limited availability of natural rubber.

As the name implies, SBR has two primary constituents, styrene and butadiene, plus some curatives and fillers. Styrene is derived from petroleum, and is a clear liquid composed of small molecules. Butadiene is a gas at room temperature and is obtained from crude oil or natural gas.

When polymerized, the two combine into long chains. If the resulting soft, sticky material is then held at an elevated temperature, (a process called vulcanization), links form between these chains that increase strength and hardness.

Properties of SBR

Developed as a natural rubber substitute, SBR has very similar, although slightly superior, properties. It’s flexible at temperatures from -40 to 180°F (-40 to 82°C), whereas rubber becomes brittle at temperatures below freezing. It’s also very abrasion-resistant, has good elastic recovery, and resists taking a compression set.

Most SBR is produced with hardness in the range of 50 to 80 Shore A. Tensile strength is 400 to 1,000 psi, although this can be increased with fabric reinforcement or by adding suitable fillers.

As for chemical and environmental compatibility, it resists most acids, plus brake fluid and water. It is however, attacked by oils and other hydrocarbons. Ozone resistance is better than that of natural rubber, although still not particularly good.

Uses for SBR

One of the biggest applications in terms of tons produced is car tires. Industrial uses include conveyor belts, bumper pads, couplings, and gaskets and seals. We stock SBR in sheet form in various thicknesses and widths and can cut it to the shape you need.

So, to recap, if you’ve ever wondered about the meaning of SBR rubber, just know that it’s like natural rubber, only without the low temperature problem and ozone sensitivity.

Rubber Gaskets, SBR Gaskets
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When Should You Ask for Butyl Rubber?

Jan 15, 2025

Synthetic rubber materials like SBR were developed to increase the supply and compensate for the limitations of natural rubber. For most of these man-made elastomers, while they excel in some regards, they fall short in others. Poor weather and ozone resistance are two of the biggest weaknesses.

Butyl rubber is a synthetic material that plugs this gap. Suitable for a range of sealing applications, it also has great damping and permeability characteristics. Here’s a closer look.

Butyl Rubber Basics

As polymerized at the factory, butyl rubber is white or colorless. It’s usually blended with carbon black to make it black, although other colors are possible.

Butyl rubber is much more dense than other synthetic rubbers, so it’s heavier, but this means it’s a very good absorber of vibration. The same chemical structure that creates high density also renders it impermeable to liquids and gases. (Other synthetic rubber materials like SBR and EPDM have a degree of gas permeability.)

Butyl rubber is on the softer side, (It’s available with Shore A ratings of 40 to 90 but is usually around 65), and has a working temperature range of -40 to 285°F. It’s also resistant to water, dilute acids, and animal and vegetable oils.

Limitations of Butyl Rubber

Butyl rubber will tend to take a compression set, limiting its use as a gasket in applications where the joint will be opened up periodically. Its abrasion resistance is only moderate and it is attacked by hydrocarbon fuels and oils.

Good Applications for Butyl Rubber

The biggest market for butyl rubber is automobile tires, where it’s used as a liner material. In terms of seals and gaskets, applications include:

  • Tank liners
  • Pond liners
  • Cushioning
  • Shock absorbers
  • Flange and full-face gaskets, especially for outdoor applications

Butyl Rubber Sheet Cut to Shape

Ask for butyl rubber when you need impermeability, weather-resistance or cushioning. Hennig Gasket & Seals has it in sheet form and a range of thicknesses. We can die, flash or waterjet cut it to the exact size and shape you need. Contact us to discuss your needs and get a quote.

Flange Gaskets
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EPDM Gaskets vs. Viton Gaskets

Jan 07, 2025

For a wide temperature range and good chemical resistance, many gasket material buyers think they have to specify Viton®. There are times when this is the right choice, but sometimes it isn’t. For many applications EPDM is a better material. This blog does an EPDM vs Viton comparison so you can decide which to use.

Chemical Comparison

EPDM gasket material and Viton gasket material are both flexible elastomers suitable for sealing gaps and joints in a wide range of applications, but chemically they are quite different. Viton is a tradename for a family of fluoroelastomers that go by the acronym FKM. EPDM, (Ethelyene Propylenen Diene Monomer), is hydrocarbon-based. During manufacture EPDM is cured with either sulfur or peroxide. Peroxide curing raises strength and the upper temperature limit.

Viton was developed by DuPont and is now a Chemours product. Chemically, its main feature is the presence of fluorine. This bonds with carbon to provide excellent resistance to chemical attack.

Property Comparison

  • Temperature range: Viton is flexible from -4 to 410°F. EPDM works from -60 to 225 or 300°F, depending on curing process.
  • Strength: Viton and EPDM are similar with a tensile strength of around 1,000psi. Peroxide-cured EPDM is stronger, up to 3,000psi.
  • Compression set: Both materials perform well.
  • FDA grades of both are available

Chemical Resistance of EPDM and Viton Gaskets

This is where the two diverge. EPDM resists:

  • UV
  • Oxidation
  • Acids
  • Alkalies
  • Ketones
  • Water and steam

Limitations are hydrocarbons and petroleum fluids, which cause swelling.

Viton resists most chemicals, except ketones, and organic acids. The latter, (substances like acetic, citric and tartaric acids), occur in food and beverage processing.

When to Use

EPDM works well in outdoor applications. It’s often used for weather stripping and dust covers, as well as mounts of various types. Another application is for low pressure boiler gaskets. FDA-grade EPDM is used in food and beverage equipment.

While Viton can be used in food processing, (subject limitations mentioned above), its main use is in fuel-handling equipment like pumps and valves. It’s also used in a lot of chemical processing equipment.

Expert Advice is Available

Specialists at Hennig Gasket and Seals are always happy to discuss gasket material applications. Contact us and let’s talk!

Flange Gaskets
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