News & Tech Tips

Selecting Custom Foam/Sponge Gaskets

The most common sponge gasket is a closed-cell rubber blend material. This material is reasonably resilient, has moderately good recovery, and is inexpensive. It can be provided plain, or with a pressure-sensitive adhesive on one side. Closed-cell sponges are available in a variety of elastomers for a wide range of applications. These materials work well in many situations, particularly those that have a constant squeeze on the gasket material.

Applications with alternating squeeze, such as doors that open and close, will benefit from using microcellular urethanes as gaskets. These materials exhibit almost zero compression set, have superior recovery, and are well suited for gaskets that have variable loads. They are particularly useful for electrical boxes and enclosures, and are available in UL listed grades for such applications. These materials, while somewhat more costly, out-perform typical closed-cell blended sponges where a seal must be maintained under imperfect seating conditions. They, too, can be provided plain or with a pressure-sensitive adhesive backing.

We stock a variety of sponge gasket materials, including Poron® and Griswold microcellular urethanes. Please contact us to discuss your application and be provided with a cost-effective solution for your sealing problem.

Choosing Basic Compressed Gasket Materials

There are several types of compressed gasket materials from which we fabricate gaskets, or provide the sheet for those wanting to make their own.

The most commonly used material we offer is Durlon® 8500, a green colored NBR binder/Aramid-Inorganic fiber compressed sheet.  Durlon® 8500 is excellent in steam, natural gas, and many petroleum based fluids, and covers a temperature range of -100 to 700ºF, with a continuous max of 548ºF.  For much of the same types of service, we offer a less costly alternate, Durlon® 7900.  Durlon® 7900 is an off-white colored NBR binder/Aramid fiber sheet with a max continuous temperature of 400º and is appropriate when service conditions are less severe.

For higher temperature steam and hot water service, we recommend Durlon® 8600, a white colored SBR binder/Aramid-Inorganic fiber sheet with a termperature range of -100 to 700ºF with a continuous max of 548ºF.

When a wider pH range is required, Durlon® 8400, a gold colored NBR binder/Phenolic fiber sheet is the logical choice.  Durlon® 8400 has a temperature range of -100 to 800ºF, with a continuous max temperature of 554ºF.   Durlon® 8400 is excellent in chemical, pulp and paper, and other industrial applications.

With the highest continuous max temperature of 600ºF, Durlon® 8300 should be considered for steam and hydrocarbon services in refining, petrochemical, and power generation industries.  Durlon® 8300, black in color, and with a NBR binder/Carbon fiber system, has a temperature range of -100 to 800ºF.

Durlon® 8700, blue in color, a CR (neoprene) binder/Aramid-Inorganic fiber sheet has the same temperature range as Durlon® 8500, but is used for refrigerants and other service requiring a neoprene binder.

There are many factors for each gasket application to consider before choosing a compressed gasket material.  Some of those include system pressure, media, temperature range, flange material and condition, flange design, and bolting.

Please contact Expert Gasket & Seal for additional assistance with your application.

Choosing Superior Durlon® PTFE Gasket Materials

There are several types of superior Durlon® PTFE gasket materials from which we fabricate gaskets, or provide the sheet for those wanting to make their own.

Durlon® filled PTFE materials are not constructed like typical skived PTFE.  Because of their unique construction, using variously shaped fillers blended with pure PTFE resin, Durlon® PTFE does not wick or cause flange corrosion.  These proprietary materials maintain a tighter seal, and have a higher bolt torque retention than other filled or conventional PTFE gasket materials.

Our most popular style is Durlon® 9000 (blue color) and Durlon® 9000N (white color).  Both of these materials are FDA compliant, are certified for Oxygen service, and are listed in “Pamphlet 95” of the Chlorine Institute as an acceptable material for chlorine service.  Durlon® 9000 and Durlon® 9000N are commonly used for gaskets in the chemical, pulp and paper, pharmaceutical, and food and beverage industries.

Another style is Durlon® 9200W, a barium sulfate filled FDA compliant PTFE is commonly used in the pulp and paper, chemcial, and other industries where resistance to aggressive chemicals is required.

Durlon® 9400 is a carbon filled FDA compliant PTFE designed for use in tankcars and chemcial plants in applications using hydrofluoric acid and anhydrous hydrogen fluoride where Durlon® 9200W is not suitable.

Durlon® 9600 is an expanded FDA compliant PTFE designed to seal at lower bolt loads.  This material, which is softer than the other Durlon® PTFE formulas, conforms easily to flanges that may be warped, pitted, or otherwise have imperfect surfaces.  Durlon® 9600 is ideal for plastic flanges using lower bolt loads, but still needing to provide a positive seal against aggressive chemicals.

These materials, designed specifically for gaskets and providing superior sealing over conventional PTFE sheets, should be considered your first choice when choosing a PTFE gasket.

Please contact Expert Gasket & Seal for additional assistance with your application.

Choosing a Rubber Compound for High Temperature Gasket Applications

There are several rubber gasket compounds for use in elevated temperature applications.  There are, as usual, many things to evaluate before selecting the proper material.

Besides the temperature range, the fluid (or media), system pressure, and exposure conditions need to be considered.  Those factors will affect the final choice, but this brief overview will highlight temperature limits.

For applications where the rubber material will not be exposed to acids, alkalis, superheated steam (over 250ºF), aromatic hydrocarbons, and certain fuels, Silicone is a good choice for the gasket you will using.  Silicone has a superior temperature range, generally remaining flexible from -75ºF to + 450ºF, and is the compound of choice for hot, dry air gasket applications.

Viton®, while not a very good compound for low temperatures, is an excellent choice in high temperature gasket applications up to approximately 400ºF.  Viton® has superior resistance to a wide variety of chemicals, including many acids, fuels, aromatic hydrocarbons, chlorinated hydrocarbons, and non-flammable hydraulic fluids.  All of the Viton® gaskets we supply are made from genuine DuPont material; not a generic FKM.

EPDM is the best rubber gasket material for steam and hot water applications to 350ºF, with some EPDM materials capable of handling temperatures in steam to 400ºF.  EPDM is not compatible with petroleum based fluids, but can handle many Glycol based fluids to 300ºF.

Perfluoroelastomers handle a wider range of chemicals than Viton®, but most commonly are available only as O-rings.  Perfluoroelastomers (the most commonly known is Kalrez®) generally are heat resistant to 600ºF, but due to their extreme expense, and limited shape and size availability, should be considered only when the application cannot be sealed with another material.

When temperatures exceed the limits noted above, it is likely a material other than rubber will be needed.

Please contact Expert Gasket & Seal for additional assistance with your application.