epdm

UV Resistant Rubber Sheet

Sep 02, 2019

You’ve probably seen dried up and cracked nitrile and neoprene gaskets. Chances are, you’ve replaced a few too! In many cases the culprit is ozone. Here we’ll explain what ozone is, how it forms and what processes/activities expose gasket materials to ozone. Then we’ll suggest materials to use if you have an ozone problem which includes UV resistant rubber sheet.

An oxygen compound

Ozone is just oxygen atoms bound together in groups of three. Its chemical symbol is O3. In nature, ozone exists only in the stratosphere, a layer of the atmosphere five to thirty miles up. However, it can be produced artificially at ground level, and those are the processes that break down nitrile and neoprene gasket materials.

Oxygen atoms react readily with other elements. That’s why iron rusts and aluminum oxidizes. O3 is even more reactive than regular O2, so oxidizes materials even faster. When it contacts gasket materials like nitrile rubber (Buna-N,) natural rubber and neoprene it changes how their polymers are crosslinked. This hardens the material, which then cracks under load.

Ozone-producing processes

Ozone forms in the presence of ultraviolet (UV) light and electrical sparks. Both can break the bonds between oxygen and itself and other elements to free up individual atoms. These quickly recombine as O3.

UV light is widely used for purification and disinfection. Many city water systems use UV purification and UV disinfection is widespread in the medical sector. Ozone is a natural byproduct and itself is used for purification.

Electrical sparks are common around brushed electric motors, especially those using high voltages. High voltage switchgear is another source of ozone.

UV Resistant Rubber Sheet

When choosing a gasket material for an ozone-producing environment stay away from nitrile rubber and neoprene. Instead, consider silicone and EPDM materials. These are available with similar properties to nitrile and neoprene but are less susceptible to oxidation. Other good choices are PTFE and Viton/FKM.

Talk to the UV resistant rubber sheet materials specialists

If you think ozone could be an issue in a gasket application, talk to our specialists. They’ll help you select an EDPM, silicone or other ozone-resistant material suitable for your application.

Applications, EPDM Gaskets, Silicone Gaskets

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Low Temperature Gasket Material

Jul 22, 2019

Many elastomeric gasket materials have a problem with low temperatures. Here we’ll look at some applications that pose challenges and suggest low-temperature gasket materials worth considering.

Low-Temperature Gasket Material Applications

Seals and gaskets are used in many low-temperature environments. One of the most common is food storage. Freezers and cold rooms are typically kept between -80 and 20°F, depending on the application. Pharmaceuticals and medical products are other industries with low-temperature storage requirements.

Industries that do product testing often employ climatic chambers. These need effective seals to minimize the expense of maintaining low temperatures, and it’s also important to consider the equipment inside. And as Chicagoland residents understand, midwest winters can challenge sealing materials used outdoors, especially if exposed to wind.

Glass transition and TR10

Polymers get their flexibility from chains of molecules moving against one another. As temperatures fall the chains are less able to move and eventually become fixed. Materials scientists call this point the glass transition temperature.

For people who need to choose and use gasket material a more useful indicator of low-temperature flexibility is the TR10 value. This was explained in, “What is TR-10 (temperature of retraction) for Gasket Material?”

Good Low-Temperature Gasket Material Choices

Oil-resistant FKM only goes down to around 5°F. NBR is useable as low as -20°F and some specialized grades will go lower. However, these aren’t low enough for many freezer-type applications. Silicon is good for temperatures as low as -65°F and fluorosilicon will go to -80°F but both are expensive. That leaves cost-effective EPDM as an excellent low-temperature gasket material.

The TR10 value for EPDM is between -49 and 9°F, depending on grade. That makes EPDM seals a good choice for many commercial and industrial low-temperature storage facilities. Furthermore, EPDM is available in FDA-approved grades for food industry use.

The chief limitation of EPDM seals is poor resistance to mineral oils and hydrocarbon products. They are good with steam and hot water though, as well as caustic cleaners.

Consider price as well as performance

In low temperatures, many gasket materials become too stiff to seal effectively. Silicon offers good performance but less expensive EPDM comes close for many applications.

Applications, EPDM Gaskets, Silicone Gaskets

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Best Gasket Material for Nitrogen

Feb 19, 2018

Many industries use nitrogen. Some users even generate their gas on-site. If your company is among them you ought to be familiar with the best gasket materials to use.

Industrial Uses of Nitrogen

Liquid nitrogen is used when very low temperatures are needed. This is often for preserving biological samples or other organic material although other uses include cooling for superconductors and to aid in machining.

Applications for gaseous nitrogen include fertilizer production, food preservation, and annealing stainless steel. It’s also used in the production of electronic components like transistors and diodes.

Nitrogen Production and Storage

Nitrogen is produced by separation from air. (The air around us is approximately 78% nitrogen.) There are two methods:

fractional distillation
pressure swing adsorption (PSA).

Distillation entails chilling air until it becomes liquid, then raising the temperature slowly to let the individual components boil. In contrast, PSA is done at ambient temperature and in simple terms consists of pushing air through a membrane that separates the various constituents.

Distillation produces higher purity gas but is energy-intensive. PSA scales more easily for local or on-site gas generation, and this is the process most often adopted by manufacturers who don’t want to depend on deliveries and storage.

Suitable Materials for Gaskets in Nitrogen Systems

Nitrile and natural rubber gasket materials are good choices for gaseous nitrogen, although EPDM is generally considered best. EPDM gasket material has good heat resistance and a working temperature range of around -60 to 320°F (-50 to 160C). Resistance to oxidation, UV, ozone, and abrasion are all good and it also withstands water, acids, and alkalies along with ketones and alcohols.

Handling liquid nitrogen demands a gasket material with excellent low-temperature performance. If an elastomer is needed Santoprene® may be a good choice. A trade name for a class of thermoplastic vulcanizate (TPV) materials, this behaves much like EDPM but some grades remain flexible at even lower temperatures.

Consult a Materials Expert

Every gasket application is different so it’s always prudent to learn more about the material before purchasing. Specialists at Hennig Gasket are ready to help.

EPDM Gaskets, Nitrile Gaskets

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