Neoprene Gaskets

Neoprene: It’s For More Than Wetsuits

Surfers and divers are very familiar with neoprene. It’s been the material of choice for wetsuits for decades. It’s also a versatile gasket material, although used in a different form to wetsuit material. Here’s what you should know about neoprene gasketing.

Synthetic Rubber

Neoprene is a DuPont tradename for polymerized chloroprene, which is one of the synthetic rubbers developed in the 1920s and 1930s. Chloroprene is composed of carbon, hydrogen, and chlorine which produce a clear liquid. Polymerization forms the molecules into long chains that interlock to create a soft, flexible material.

Neoprene is made as a solid, (described as homogenous neoprene,) and closed-cell foam. It’s this latter version that’s used in wetsuits with the pockets providing thermal insulation. Foamed neoprene provides good cushioning and is used for gasketing as it forms a soft, waterproof seal. (Pressure-sensitive adhesive applied to one or both sides makes it easier to fix in place.)

Neoprene is also used as a binder with Aramid fibers. This results in a higher-strength neoprene gasket.

Neoprene Properties for Gaskets

Being soft, (40 – 70 Shore A durometer,) and flexible with good elastic recovery, homogenous neoprene conforms readily to mating surfaces. It has excellent water resistance, (hence the wetsuit usage,) and also withstands oils, ozone, and some acids. Food grades are available.

The practical temperature range for neoprene gasketing is -20 to 180°F. This makes it unsuitable for sealing steam or other hot fluids. A bigger limitation is a lack of strength. Depending on grade, maximum tensile strength is 900 – 1,000 psi, meaning neoprene is not suitable on its own for high-pressure applications. Bound with Aramid though, it offers much higher strength.

Ask Us About Neoprene Gasketing

Homogenous neoprene comes in sheet and roll form up to 72” wide and in a range of colors. Thicknesses range from 3/32” up to 2”. We can waterjet, flash, or die-cut neoprene to the size and shape you need. If you’re looking for inexpensive gasket material and don’t need high strength, neoprene may be the gasket material for your application. Call us to discuss.

Gasket Material for Natural Gas

Natural gas is widely used for heating and cooking and it’s the energy source for much of our electricity. Perhaps less well known, it’s also essential for fertilizers and plastics.

The systems that store and distribute natural gas need gaskets. Here we’ll discuss the materials most often used, but first, a short primer.

Hydrocarbon Origins and Uses

Like coal and oil, natural gas is formed from plant and animal remains. Decomposition produces methane, (CH4), and when trapped underground we call it natural gas. Natural gas is odorless, so a trace of mercaptan, (CH4S) is added to make it detectable.

Reacting natural gas with steam separates the hydrogen and a second reaction, this time with air, results in NH3, or ammonia. Chemists call this the Haber process and it’s the first step in producing fertilizers.

Like methane, plastics are also composed of carbon and hydrogen atoms. The difference is that the atoms are formed into long chains to create polyethylene, polypropylene and similar materials.

Storage and Distribution

When held above 200 bar (3,000 psi) natural gas is known as compressed natural gas (CNG). This makes it sufficiently dense for use as a vehicle fuel. When pipelines aren’t an option, for easier transportation cooling to below -184°F produces liquefied natural gas (LNG).

The Sealing Challenge

The biggest issues are permeability and flammability. Simply put, the very small methane molecules can find their way through some materials, and they burn readily. Fortunately, as it’s lighter than air, escaping natural gas tends to disperse quickly.

Sealing CNG and LNG presents additional challenges. Gasket materials must retain some flexibility at very low temperatures and should have the strength to resist extrusion through joint faces.

Materials for Natural Gas Gaskets

For most low pressure, ambient temperature applications nitrile and neoprene gasket materials are the first choice. In more challenging applications many engineers opt for more expensive Flexitallic spiral wound gaskets. PTFE and graphite are other options.

Every gasket application has some unique challenges. If you need material for natural gas gaskets, ask a product specialist at Hennig Gasket for advice.

Neoprene Gasket Applications

Neoprene is a synthetic polymer that resembles rubber, but as a derivative of chloroprene, it is far more durable in extreme temperatures, when exposed to oils and several chemicals, and it endures harsh weather conditions. But not all Neoprene gaskets are created equal—there are several variations or “grades” of neoprene. Each grade of neoprene gasket has its ideal application depending on factors such as temperature and pressure tolerances, the environment where it will be used, etc:

  • Commercial Grade Neoprene—15-50% Neoprene mixed with other elastomers; this blend is fine for general commercial gasket applications, but not in situations where high oil resistance is necessary.
  • Medium Grade Neoprene—51%+ Neoprene content; also suitable for many general manufacturing applications where a lower tensile strength will suffice.
  • High Grade Neoprene—100% Neoprene is extremely resilient in the harshest, most demanding environments while maintaining its resiliency, abrasion resistance and tensile strength.
  • FDA Neoprene—A mixture of Neoprene and other FDA-improved materials; gaskets made from this grade are used in the food industry, but also in many government-approved and military applications where oil resistance is key.
  • PSA Ready Neoprene—Available upon request, this Neoprene has one side with a matte finish and is designed to be used with pressure sensitive adhesives.
  • Nylon Cloth Inserted Neoprene—This grade is reinforced with one or two layers of nylon; good for improved creep reduction and stability.
  • Diaphragm Neoprene—Polyester insertions improve performance under high pressure applications requiring high levels of oil and petroleum resistance.
  • Flame Resistant Neoprene—Especially useful in potentially flammable, electric and high-heat applications, it passes the following flammability specifications: UL-94-HF-1, UL-94-HFB, MIL-R-6130C, FMVSS-302.

These grades vary in durometer ratings between 40, 50, 60, 70 and 80, can withstand temperatures between -20F to +180°F and come in sheets with several widths and thicknesses that can be cut (waterjet, flash and die cut) to exact specifications from your blueprints, or even reverse engineered.

Please contact Hennig Gasket & Seals if you have any questions about the different grades of neoprene that might best fit your application: 1-800-747-7661. We can custom manufacture any neoprene gasket you need to the most accurate specs possible.

What is Neoprene

Possibly the most widely used (and certainly the type we’re asked for most), neoprene gaskets are a good choice in many applications. However, they do have some limitations. It’s easier to understand when and when not to use neoprene gaskets if you know something about the material. Here we’ll answer: What is Neoprene? What makes neoprene so useful in many gasket applications? And when you should look for something else.

Rubber-Like Elastomer

In the 1930’s and ‘40’s scientists cooked up several types of artificial rubber. Styrene-butadiene rubber (SBR) and nitrile-butadiene rubber (NBR) are two of the best known. A third was neoprene. Like NBR and SBR, it’s mainly carbon and hydrogen, but has chlorine added to each molecule. That makes its chemical name chloroprene, or polychloroprene once polymerized. The ASTM D1418 designation for neoprene, which was DuPont’s tradename, is CR. The ASTM D2000 type and class is BC and BE, depending on the specific grade.

Useful Properties of Neoprene

The first ASTM D2000 letter tells us the upper-temperature limit of neoprene is 212°F (100°C). The lower temperature limit is around -30°F (-34°C), although neoprene becomes stiffer before getting that cold. The second letter indicates that it is prone to swelling when exposed to oils.

Neoprene does, however, resist attack by mineral and vegetable oils. It’s also resistant to ozone and weather aging, making it useful in outdoor applications.

It takes relatively little force to deform, which helps make neoprene gaskets versatile. Shore A durometer numbers are typically 50 – 70, meaning it’s quite soft. (Learn more about Shore and Durometers in, “Understanding Gasket Material Hardness” and “Measuring Gasket Material Hardness.”)

Neoprene Limitations

Aromatic hydrocarbons like benzene and toluene will degrade neoprene, as will ketones and chlorine-based chemicals. While it has many uses, neoprene should not be used with food.

Neoprene Material Forms

Neoprene gaskets are typically cut from sheet material. A range of thicknesses and hardnesses are available. Neoprene can also be foamed and is available in both open and closed-cell forms. This has the advantages of lower density and greater compressibility. Hennig material specialists can provide more details.  Contact us for your custom neoprene gasket material needs.

ASTM Testing for Creep Relaxation

Open an electrical enclosure and you may see that the neoprene gasket material has taken on the imprint of the door or cover. In technical terms, it’s taken a compression set. In many gasket applications compression set can lead to sealing problems, due to a phenomenon known as creep relaxation.

Introduction to creep

Apply a load to an elastic material and it compresses. This happens because unlike in a metal, the atoms are linked in a way that lets them move. In gasket materials this is good because it lets the gasket deform to take up the irregularities between the two surfaces being sealed. However, there is a downside to this compressibility.

Rubber and rubber-like materials, as used in neoprene gaskets for example, have the ability to spring back. Release the load and the material returns to its original shape, more or less. Some materials do this better than others. The issue is that the material takes on a permanent deformation, or worse still, continues to deform. This behavior is called “creep” or more accurately, “viscoelastic creep.” It’s related to both the strength of the material and the time and temperature to which it’s subjected.

When creep is a problem

In a bolted joint the compressed gasket creates the torque in the securing bolts. But as the gasket material creeps and the gasket thins, the bolts are able to relax. That reduces the torque and the joint begins to loosen.

Polyurethane, silicone and nitrile gaskets tend to have lower creep than some other materials, as quantified by testing to ASTM 38.

ASTM testing

The principle is to measure the thickness of a sample of gasket material, subject it to load, temperature and time, then release the load. The recovered thickness is measured and the difference used to calculate a percentage reduction.

Taking creep relaxation numbers into account when choosing gasket material.

As with testing to ASTM 36, the absolute test values are less important than the ability to make comparisons between gasket materials. It’s a parameter of particular importance when lasting bolt tightness is essential.

Why Thinner Gasket Material Usually Works Better

Gasket materials come in many thicknesses. To give one example, at Hennig Gasket neoprene gasket material is available from 3/32” all the way up to 2” thickness. Customers will sometimes ask what thickness they should buy, but a gasket material supplier really can’t help with that. It depends completely on the application. However, it’s generally agreed that a gasket should be as thin as possible, providing it still seals. There are four reasons. A thinner gasket:

1. Has greater blow-out resistance. Being thinner, the gasket present less area to the internal pressure, so is less prone to deformation and failure.

2. Has a lower leak rate. All gaskets will allow some quantity of fluid to pass through. This is just a natural function of their structure and the make-up of the fluid being constrained. (Anyone who’s ever tried piping helium knows how its small molecules let it escape from almost anywhere!) So the less gasket material that’s exposed to the fluid, the less will leak.

3. Retains fastener torque better. This stems from the creep relaxation characteristics of the gasket material. When there’s less thickness there’s less creep, (think of it happening on a percentage basis,) so more torque is retained.

4. Is less expensive. Material cost relates more to volume or weight than area, and thicker gaskets need more material. Secondly, thickness also influences cutting method and thicker materials could be more expensive to cut to shape. Neoprene gasket material 3/32” thick die cuts readily, but a thickness of 2” may call for a waterjet.

Note though that points 1 and 2 really only apply to situations where the gasket resists pressure, such as in pipelines. In no-pressure situations such as a gasket sealing around an electrical enclosure, the benefit is primarily Point 4 – cost.

All About the Gap

How thick a gasket should be depends entirely on the application. Remember that it’s purpose is to take up an uneven gap between two surfaces. The key is having enough thickness that the gasket compresses and fills the voids, but no more.

How Hot is too Hot? Choosing the Right Gasket Material for a Non-Metallic Gasket

For non-metallic gasket applications, the operating temperature of the finished product is a major consideration. You need to know the temperature range (and other strengths and weaknesses) of potential materials so you can get the most durable custom gaskets and seals. Otherwise, they could prematurely harden, crack, deform and lose strength, elasticity and resilience, etc.

The following is a list of common non-metallic gasket materials, their properties and their most stable operating temperature ranges (in Fahrenheit). Understand that while there may be wiggle room on either end, it’s best to aim for somewhere in the middle of each particular material’s temperature range so that the gasket or seal performs optimally for the longest period of time before replacement is needed.

Nitrile: -30 to 250F (very resistant to oils, aromatic hydrocarbons, fuels and solvents).

Neoprene: -35 to 225F (resistant to weather, water, combustion and a long list of chemicals).

Polyurethane: -35 to 225F (resistant to oxygen, ozone, cracking, abrasion, cuts, grease and heavy loads; frequently used in machine mounts, electrical equipment wear pads and applications needing shock absorption).

Ethylene Propylene: -70 to 250F (resists severe weather conditions, acids, oxygen, alkalis, hot and cold water and ketones; not suitable for use with oils or fuels).

Fluorocarbon: -15 to 400F (its low friction and resistance to wear and tear make this a good material for gaskets that endure movement, a wide temperature variation and frequent reassembly).

Silicone: -65 to 450F (very resistant to hot, cold and oxygen, but poor resistance to oils and fuels; frequently used in food processing and medical applications).

Polytetrafluoroethylene: -238 to 574F (extremely wide temperature range, also stands up to harsh conditions of all sorts; frequently used in food processing, pharmaceutical, laboratory, semi-conductor, petrochemical and chemical and electrical applications).

Temperature range is, of course, just one aspect of a non-metallic gasket material that you will need to consider before project implementation; nevertheless, temperature tolerance is crucial. If you need custom gaskets and seals for your project, please call us at 1-800-747-7661 to discuss your needs with us.

Properties of Neoprene Gasket Material

Neoprene, which is also known as “polychloroprene,” is a type of synthetic rubber produced by the polymerization of chloroprene. Neoprene gasket material has become very common due to the fact that it resists the likes of ozone, sunlight, oxidation and many petroleum derivatives. Additionally, neoprene is characterized as being weather-, combustion-, water- and chemical-resistant. As you can see, it’s popular because it is resistant to many types of damages. What’s more, it’s also resistant to damage from twisting and flexing.

Here’s a closer look at the properties of neoprene so you can judge whether or not it’s a good material for your application:

  • Stretch and cushioning properties: Neoprene is elastic and form-fitting, able to conform to various sizes and shapes. It’s also cushioning, able to absorb shock.
  • Various grades available: From cloth inserted neoprene, which is reinforced with nylon for additional stability, to flame retardant neoprene, which passes a variety of flammability specifications, there are several grades available to suit any application. Other popular grades include commercial, FDA approved, diaphragm and high tensile strength.
  • General gauge thicknesses vary in size from 3/32-inch up to 2 inches.
  • Hardness ratings vary from 40 to 80.
  • Plate finish.
  • Neoprene can withstand temperatures ranging from -20 degrees F to 180 degrees F.
  • Tensile strength ranges from 900 to 1,000 PSI.
  • Elongation ranges from 350% to 400%.
  • Finally, widths are 36 inches, 48 inches or 72 inches.
  • Pressure sensitive adhesive, or PSA, are available upon request.
  • We fabricate neoprene gaskets through proven manufacturing processes that include waterjet cutting, flash cutting and die cutting.

One other neat feature about neoprene is that it’s impermeable, meaning that it can work as a tight barrier to prevent the escaping of gases or liquids.

For more information on the neoprene material and neoprene gaskets, and to speak with someone about placing an order, contact us today.