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The Elastomerics Blog by Stockwell Elastomerics

Thursday, September 03, 2015

What is foam compression set?

In simple terms, compression set is a measure of how much a material does NOT rebound.  This is expressed in a percentage, for gasketing, the lower % the better (to ensure "apples and apples" confirm test temperature).

Why do we care about compression set?
Compression set, sometimes called C-set, is an indicator of how a material behaves under certain conditions.  The compression set test for foams and sponges include a 50% compression at various temperatures.  Room temperature 23°C, intermediate 70°C, and high (100°C for silicone).  Since heat is an “accelerator” of compression set, an engineer would roughly relate these temperatures to their application.  A gasket material  that takes a C-set at elevated temperature will quite often stop functioning as a gasket over time.  This would be metered against the expected life of the product, whether there is re-compression, level of sealing (e.g. NEMA 4X vs NEMA 3R), preventive maintenance, cost, and most important the cost of a leak/equipment failure due to a leak.

Below is a graph produced by Rogers Corporation, this shows compression set values of different gasket materials at different temperatures, silicone is tested at a higher temperature (100°C) since it is considered a high temp gasket material and resist the effects of heat.

 Compression Set of Foams

Example application:  
A couple years ago Stockwell had a customer who had remote monitoring equipment in the desert;  the only way to access the enclosures for this equipment was by helicopter.  The gasket needed to seal under desert conditions; temperature cycling, rain sealing, dust sealing, and not be affected by ice. The cost to access and repair the equipment would have been enormous.  Stockwell’s Applications engineers recommended a closed cell silicone foam material that could withstand high temperatures without taking a compression set.  Had the application been for a piece of lab equipment, a very different material may have been selected.

Rubber Compression Set in summary:
Compression set is just one data point that follows an ASTM test procedure in order to help engineers distinguish the performance properties of various materials on an even playing field.  There are many other factors and key properties to sealing successfully such as stress relaxation and cell structure that need to be considered for the overall best gasket material choice.  Selecting a commercially available material and how to use it can be daunting, Stockwell’s Applications Engineers are available to discuss your project.

For Applications Engineering assistance or more information on low compression set rubber, sponge and foam, please contact Stockwell Elastomerics at 1-800-523-0123 or email

Additional information on Creep, Compression Set, and Stress Relaxation

posted by Steve Hughes at 10:41 AM comments

Thursday, August 06, 2015

New Poron Webpage

Stockwell Poron
Poron Urethane Foam - Stockwell Elastomerics
As a manufacturer of gaskets and pads made from high performance materials, Stockwell Elastomerics is a proud supplier of Poron urethane foams.  Poron is manufactured by Rogers Corporation and brought to market through a select network of converters who have been educated on the use of Poron as well as understand the value it brings to customers.  Stockwell Elastomerics is a Rogers Preferred Converter and maintains inventory of the industrial Poron foam grades.

Stockwell has a newly updated webpage to help designers and engineers understand and select a Poron grade that best fits their applications.  And as always, Stockwell’s Applications Engineers are available to answer questions about Poron foam and other material options that may be suitable for your project.


Poron foam uses:
  • Poron enclosure gasket
  • Poron dust gaskets
  • Cleanroom gaskets
  • Poron cushion pads
  • Poron touchscreen gasket
  • Poron battery cushion pads
  • Gap filling foam for electronics
  • Poron shock absorbing pad
  • Poron foam gaskets - light water exposure
  • Light leak gaskets

For more information about Poron urethane foam or other high performance gasket materials, please contact Stockwell Elastomerics at 1-800-523-0123 or email

posted by Steve Hughes at 1:49 PM comments

Monday, July 13, 2015

Double Sided Tape for Gaskets

Poron with 3M 200MP
Stockwell Elastomerics is a custom gasket manufacturer who specializes in high performance materials.  A part of a gasket that is often overlooked is the adhesive backing, we hear it called a peel and stick backing, sticky backed gasket, adhesive gasket or some version of these. What many customers don’t realize is the adhesive backing, in most cases, are double sided tape.  As a 3M Select and Adchem converter, Stockwell maintains inventory of master logs of double sided tape. These adhesives, usually referred to as pressure sensitive tapes (PSAs), are applied to most of Stockwell’s materials (including silicone rubber).  Most master logs are self-wound; this means when unwound, one side of the adhesive is exposed.  The exposed side is bonded to the rubber material; the non-exposed side has liner (usually paper or plastic) that is peeled of when the gasket is installed.

How can adding adhesive save cost?
1) Producing the part - in some cases, having an adhesive backing allows gaskets and pads to be produced on equipment that can run faster.  Usually due to the fact that the adhesive liner helps prevent the rubber material from stretching during processing.

2) Assembly throughput – for mid and high volume production, gasket or pads can be supplied kiss-cut on a roll.  Kiss-cut parts allow for easier and faster installation of the gaskets.  The time saved in throughput usually offsets the added cost of the adhesive and in most cases offers cost savings.

The best adhesive for gaskets
Call Stockwell’s Applications Engineers – it’s fairly cliché, but the devil is in the details.  Temperature, bond strength, surface energy, surface texture, chemical exposure, reinforcement, cost… are points to consider.  Stockwell’s engineers work closely with customers and  3M to ensure the proper adhesive is selected for each applications.

Types of gasket adhesive backings:

  • General purpose adhesive
  • Film supported adhesive
  • Low tack or repositionable adhesive
  • Low surface energy adhesive
  • Very high bond (VHB) adhesive
  • High temperature silicone adhesive
  • Thermally conductive adhesive
  • Electrically conductive adhesive

For more information about adhesives for gaskets and pads, please contact Stockwell Elastomerics at or call 1-800-523-0123.

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posted by Steve Hughes at 1:44 PM comments

Wednesday, June 17, 2015

Soft Silicone Rubber for Sealing to IP67 & IP68

IP67 is a rating often associated with ruggedized electronics, outdoor lighting fixtures, and other enclosures requiring a high level of sealing.  Stockwell Elastomerics manufactures custom rubber components for OEMs where reliable, long term IP, NEMA and UL sealing requirements are critical.
IP67 Gaskets

IP67 requires an enclosure or housing to be dust tight (6X) and protect against water ingress (X7) when submerged up to 1 meter for 30 minutes; for many electronic manufactures, this is considered a minimum requirement.  When a rugged device is designed the expectation is that it will be able to survive a longer submersion period and withstand a range of environmental conditions.  Taking into account temperature extremes, drop tests, accelerated aging, and other conditions, silicone rubber is one of the best materials for sealing to IP67.

Silicone rubber is a very versatile elastomer, it is readily available in soft, low durometers such 10, 20 on the Shore “A” scale, even softer closed cell silicone sponge is also available.  These soft silicone grades are preferred since they easily conform to enclosure variations and “absorb” tolerance stacks, sealing under lower clamp pressures.  These lower clamp forces are key for plastic and thin metal enclosures that can deform under too much load.  This deformation quite often creates unintended ingress points.

In addition to their low durometers, soft silicone rubber can be molded or cut from sheets.  Silicones are inherently UV and ozone resistant, and have wide operating temperatures.  On the low temperature side, silicone will remain compliant and functional below the glass transition point of other elastomers.  On the high end of the temperature range, silicone is very stable, this stability helps resist compression set and stress relaxation where other polymers would take a compression set or permanent deformation.

Key features of Silicone for IP67:

  • Soft, low durometers are standard
  • UV resistant
  • Ozone resistant
  • Wide operating temperature
  • Can be cut or molded
  • UL94 HB flame rated,20 duro sheet materials
  • EMI attenuation (conductive grades)

Sealing to IP67 and other IP, NEMA and UL50 standards can be difficult.  Stockwell Elastomerics’ Applications Engineers work closely with OEM design engineers to help select the best material for their enclosure project.

For more information on IP67gaskets, soft silicones or other enclosure gaskets, please contact Stockwell Elastomerics by email at or call 1-800-523-0123

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posted by Steve Hughes at 3:29 PM comments

Thursday, May 14, 2015

What is Strip-N-Stick?

Many years ago the Connecticut Hard Rubber (CHR) developed Strip-N-Stick™, an expanded silicone sponge with a silicone based adhesive backing.  Through a web of acquisitions, CHR was acquired by Saint Gobain Performance Plastics who currently manufactures the Strip-N-Stick™ family of products.  Strip-N-Stick options have expanded over the years to include acrylic adhesive, reinforced silicone sponge, open cell silicone foam and solid silicone rubber.
Gasket Tape
Strip-N-Stick & Stockwell Gasket Tape

Strip-N-Stick is widely used for enclosure gaskets, large radome gaskets, cushioning strips and many other applications where a conformable gasket tape is needed.  Stockwell Elastomerics is a preferred St. Gobain distributer / converter, with master log inventory.  While common widths for Strip-N-Stick are 1” and 0.75”, Stockwell Elastomerics cuts all Strip-N-Stick and gasket tapes to width at the time of ordering.  This helps ensure good inventory turns and fresh adhesive.

Most popular Strip-N-Stick gasket materials:
 SNS-100S – Medium Closed Cell Silicone Sponge Tape, Silicone PSA
 SNS-200A – Medium Closed Cell Silicone Sponge Tape, Acrylic PSA
 SNS-300AR – Medium Closed Cell Silicone Sponge Tape, Reinforced

An interesting side note about the name Strip-N-Stick… it came from a contest where samples were sent to distributors who were asked to name the product.  Stockwell was one of the submitters but for better or worse, was not the winner but is one of the few remaining original suppliers.

For more information about custom silicone gaskets and cushioning pads fabricated from St. Gobain COHRlastic materials… transitioning to NORSEAL silicone materials, please contact Stockwell Elastomerics at 1-800-523-123 or email

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posted by Steve Hughes at 4:52 PM comments

Tuesday, April 28, 2015

Best Gasket Manufacturer

Over the years Stockwell Elastomerics has received a lot a compliments, we recently had a customer tell us that Stockwell is the best gasket manufacturer… while it’s great to hear we’re appreciated, “the best” is certainly hard to quantify.  Stockwell Elastomerics has been in business for almost 100 years, and over the years competitors have come and gone.  There are many great gasket fabricators in the U.S. and around the world, the better manufacturers tend to have an area of expertise or strong core competence. Others try to be all things to all people, which more often ends up with under

served customers.  With so many elastomers, variants of elastomers and processing combinations, it’s extremely difficult to have an expertise in all these areas.  Stockwell Elastomerics has selected high-performance, engineered materials as their core competence, with a concentration on commercially available silicone rubber materials.  What does that mean?  Stockwell has partnered with the top material manufacturers like Rogers Corporation, St. Gobain Performance Plastics, Wacker Silicone, Momentive Silicones, Specialty Silicone Product, 3M, and Adchem to bring customers the best performing products available.  Moreover, Stockwell Elastomerics has committed to keeping inventory so they can respond quickly to customers’ urgent needs.  This rapid response model has been institutionalized within the company; it’s understood that the gasket is often the last component specified.  Stockwell works closely with their customers to understand the technical performance needed as well as their timeline… Stockwell Elastomerics is committed to meeting both.

For more information about Stocwell Elastomerics' products and services, please call 1-800-523-0123 or email

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posted by Steve Hughes at 5:34 PM comments

Thursday, March 26, 2015

Super Resilient Extreme Temperature Silicone Foam

Super Resilient Extreme Temperature Silicone Foam – Stockwell Elastomerics has it! Silicone foam, not to be confused with silicone sponge, is a platinum cured (addition cured) liquid silicone rubber that is expanded.  Silicone as an elastomer is very resilient, especially when compared to organic elastomers such as chloroprene. This is attributed to free volume in the molecular make up of silicones that allows the polymer to move more freely making the elastomer more flexible and resilient.  This free volume also gives silicones a lower glass transition than organic (carbon backbone) materials, meaning they can naturally perform at lower temperatures without plasticizer. In addition, the Si-O backbone is stronger and less susceptible to breakdown in high temperatures, UV and ozone environments.

Super Resilient Extreme Temperature Silicone Foam is a good description for Rogers Corporations’ HT-800 family of silicone foam products.  In addition to being super resilient and having excellent temperature properties, they are formulated in various firmnesses and carry a UL 94V-0 flame rating. HT-800, HT-820 and HT-840 are considered closed cell and are qualified by UL for enclosure gaskets, with UL50 and UL50E recognition.

Below is a list of performance properties for HT-800 silicones… it’s easy to see why these are usually the best gasket materials for indoor and outdoor enclosure gasket applications.
  • Super resilient (low compression set)
  • Extreme temperature range
  • UV & ozone resistant
  • UL 94V-0 flame rating
  • UL 50 and UL 50E gasket rating
  • Inherently fungus resistant
  • Closed cell foam for water sealing
  • Long life rubber
  • Available with or without adhesive from Stockwell Elastomerics
  • Competitively priced
Silicone foam sheet materials like HT-800 are widely used to seal and ruggedize electronic and electrical enclosures when regulatory compliance and long term performance is critical. Stockwell Elastomerics maintains inventory of the HT-800 silicone foam family of materials and applies high quality 3M adhesives as needed. Stockwell also waterjet cuts and die cuts custom gaskets from resilient silicone foam and silicone sponge sheet rubber. In addition, Stockwell Elastomerics manufactures slits rolls for gasket tape applications.

For more information about Super Resilient Extreme Temperature Silicone Foam, closed cell silicone sponge, and other high performance gasket materials, please call 1-800-523-0123 or email

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posted by Steve Hughes at 3:05 PM comments