Extruded Gaskets

Extruded conductive elastomer or rubber gaskets are available in variety of cross section, they can be both solid and hollow strips. Gasket profiles are now a days tailored according to application methods, ultra-low closure force or to suit large deflection ranges.

Gaskets are produced from extruded rubber and is used for prevention of leakage of fluids or gases, under the impact of extreme temperature or pressure. Extruded gaskets are today are used in a variety of applications. The extruded gaskets gives the users a variety of choice regarding shapes and design. Some of the types that are available these days include spiral wound, sheet or die-cut, gasket strip, sanitary gasket, spiral wound, window gasket etc. Sanitary gaskets have been successfully applied in pipeline systems in the critical industries of food, pharmaceutical and bio-tech industries. Some of the typical gaskets as used in industrial applications are shown below.

These days gaskets are co extruded for combining dual purpose along with simplicity. These Co-extruded gaskets provide optimum EMI shielding and excellent protection against corrosion in a single yet cost-effective design. The outer gasket that is non-conductive plays the role of an extra environmental seal. This is to ward off the moisture from conductive gasket/flange interface. A specific advantage of the Co extruded profiles is cost effectiveness. Co-extruded gaskets allows the use of existing flange designs. They provide for attachment of gasket through a less expensive nonconductive elastomer.

Materials for Extruded Gaskets
Some of the materials that are typically used for extruded gaskets are discussed here. First is TPE or Thermoplastic Elastomers / TPV (Thermoplastic Vulcanizates).

Thermoplastic Elastomers / TPV (Thermoplastic Vulcanizates)
These are materials that have been created to match the best properties of rubber along with the flexibility and ability for easy processing as in thermoplastics. Perhaps that is the reason why they are used for gasket applications in place of EPDM and other rubber based products. Some of the properties that gives them an edge over others include:

Silicone Rubber
Silicone rubber is an excellent source for gasket materials. Silicone extruded door gasket is quite popular in a number of industries. Silicone gaskets offers the advantage of excellent resistance to a wide temperature range from -80° C to +250°C. Silicone sponge is made int extruded gasket profiles that are soft and easy to compress. Making them most appropriate for enclosure and door sealing.

Application of Extruded Gaskets
The extruded gaskets are used in a number of popular applications, some of the major ones are highlighted here for a quick reference.

Refrigeration
A very good application of the extruded gaskets lies in its application as door gaskets in the refrigeration industry. Other similar applications included freezer door gaskets as well as cooler door gaskets.

Plumbing operations
Co-extruded gaskets are used for pipes made with PVC, Polyethylene and concrete. The following image shows a Co-extruded gasket system that is utilizing a dual durometer design. This not only gives a superior sealing but also comes at a lower cost.

 

Window Profiles
Coming to the housing sector co extruded/extruded gaskets are used in window profiles.

Other Industries
Other industries served include the critical communications industry where it is used in the commercial as well as military communications equipment. Extruded Rubber Gasket's use in Antenna system of a passenger car.

Case Study on the effectiveness of Co extruded gaskets

The Challenge
The challenge was for a pole-mounted, aluminum telecom enclosure. There was need to control EMI and to keep out the elements. The said enclosure required a conductive gasket that shows a capability of at the least 80 dB shielding effectiveness in high-low megahertz range. Along with that there was need for a separate environmental seal for protection against rain and moisture.

 

Common Approach Undertaken
At first a hollow silicone strip which is non-conductive and filled with a pure-silver silicone was extruded on to its surface. What happened was that on getting contact with the aluminum housing, along with exposure to coastal salt fog and driving rain, there was severe occurrence of the corrosion of housing flanges.

Effective Approach for Remedy
To rise up to the challenges of shielding and environmental requirements, a co-extruded EMI gasket was used. A conductive elastomer was extruded in parallel with an elastomer that was non-conductive. The conductive side of the gasket is nickel-plated-graphite and filled with silicone. The filler particles have the capability to bite through the thin surface oxides as well as the chemical treatments on aluminum housings. Long term integrity is provided by the vulcanized seam between the elastomers. The conductive side of the Co extruded gasket is placed inboard, while the non-conductive silicone is positioned outboard.

The cross section's non-conductive side is specifically designed for an additional sealing tab that fills the existing sump area in the seam for collection of rain and moisture. The efficacy of the Co extruded gasket lies in the following:

Tags:- Co-extruded Gasket System, Extruded Gaskets Manufacturers

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