The Elastomerics Blog

Rogers purchase of MTI / Groendyk Silicone Sheet Operations

2009-05-26T17:11:00.004-04:00

One of Stockwell Elastomerics’ strategic channel partners is Rogers Bisco™ Silicone Materials Unit. Bisco is our leading provider of Silicone Foam and thin Liquid Silicone Rubber Sheet materials for gaskets, cushioning pads and custom components.

Rogers recently acquired certain assets of MTI’s Groendyk Silicone operations. Groendyk has been producing closed cell silicone sponge and solid silicone sheets for many years. MTI has been casting Open Cell Silicone Foam as well. Rogers’ acquisition will further enhance their leadership position in the marketplace and provide a presence in the closed cell silicone sponge market.

During periods of transition – there may be gaps in material availability of the traditional MTI / Groendyk Silicone Sheet product line. As situations occur – Stockwell Elastomerics may be able to help customers in tight inventory situations. See the following cross listing as a reference – we are glad to supply evaluation samples.

MTI Siltec-SD can be matched by Bisco BF1000 lightweight silicone foam
MTI MF8000 can be matched by Bisco HT800 medium density silicone foam
MTI MF8500 can be matched by Bisco HT820 firm density silicone foam
Groendyk 7104 can be matched by Cohrlastic® R10480-S soft closed cell silicone sponge
Groendyk 7304 can be matched by Cohrlastic R10470-M medium density closed cell silicone sponge
Groendyk 7404 can be matched by Cohrlastic R10470-F firm density closed cell silicone sponge
Groendyk 7314 can be matched by Cohrlastic R10400-M medium density, flame retardant closed cell silicone sponge.

Further – Stockwell has over 15 acrylic adhesives to aid in assembly of gaskets and cushioning pads.

For more information about silicone sponge, silicone gaskets, or other silicone rubber applications, please contact Stockwell at (215) 335-3005 or visit our website at stockwell.com.

Fluorosilicone – Fluorosilicone Sponge, Solid Fluorosilicone, Electrically Conductive Fluorosilicone

2009-05-18T11:07:00.006-04:00

Fluorosilicone (FVMQ) is fluorinated version of silicone which gives this polymer superior chemical resistance. Fluorosilicone is used where extreme temperature ranges (relative to “rubber”) are required and where aggressive fluids may be present.

The Aerospace, Automotive and Green Energy industries often use fluorosilicone for its cross-functionality. Fluorosilicone has ability to maintain its mechanical properties over a wide temperature range, is UV and ozone resistant and has excellent chemical resistance particularly to fuels and oils.

Stockwell offers fluorosilicone in its many forms including solid fluorosilicone sheets, soft fluorosilicone sponge, molded fluorosilicone parts, and electrically conductive fluorosilicone (used for EMI gaskets). Sheet grades are readily die cut or waterjet cut on site. Similarly, fluorosilicone parts are molded onsite at Stockwell Elastomerics.

For more information about solid fluorosilicone gaskets, fluorosilicone sponge, or other gasket fabrication applications, please contact Stockwell at (215) 335-3005 or browse our website.

Link to: fluorosilicone datasheets

Fast Gasket, Quick-Turn Gasket, Next Day Gasket, or Quick Gaskets!

2009-04-23T14:08:00.010-04:00

It is not a rare occurrence at Stockwell to receive an urgent call requesting next day gaskets or pads. Many times there is field requirement or engineering build where time is critical. Stockwell inventories a wide range of materials and thicknesses. Stock materials include solid silicone, closed cell silicone sponges, UL rated silicone foams, Neoprene sponges, EMI gasket materials, and Thermal management materials just to name few. These stock materials in combination with 3 in-house water jet cutting, die cutting and molding presses with 12” x 12” sheets molds, allow for quick response to urgent request.

Helpful hints for fast gaskets to fix a problem or meet a deadline:
- Supply an electronic CAD file (2D .dxf or 3D .iges)
- Work with in-stock materials
- If an adhesive backing is required, inform us of the type of metal, plastic or painted surface to be bonded to
- Indicate smallest quantity required
- Provide ship-to information and carrier account number- Supply a credit card or purchase order (existing customers)

Providing an electronic CAD file helps expedite the Water Jet programming. With a wide cross section of materials in stock, Stockwell can usually find a material to meet gasketing requirements. Since it is often a race against the clock / shipping pickup, knowing the minimum quantity helps to manage processing. Often additional parts can ship within a few days.

Jointed Silicone Gasket

2009-02-16T10:12:00.007-05:00

In June of 2006 I posted a brief description for Material Jointing. This shows two methods used to joint silicone sheet, the one being a combination edge/lap joint. Stockwell joins silicone sheet regularly for large gaskets that exceed standard silicone sheet manufacturing widths. Below are pictures of an edge/lap joint made from a high tear strength class 3 silicone (ZZ-R-765, Class 3B Grade 50). Also shown is a large dome gasket which Stockwell custom fabricated using edge and lap jointing methods.

For more information about silicone jointed gaskets, silicone gaskets, or other gasket fabrication applications, please contact Stockwell at (215) 335-3005 or visit our website at stockwell.com.

BF-2000 Ultra Soft Silicone Foam

2009-01-08T13:21:00.005-05:00

Previously called EP-2022, BF-2000 Ultra Soft Silicone Foam (liquid silicone base) has been a nice addition to Stockwell’s line of silicone products. With a typical force deflection of 1.5psi required to deflect the material 25%, it is the softest silicone foam product currently offered by Stockwell. BF2000 has excellent rebound (compression set resistance), a wide operating temperature range, is UV resistant and is UL94 V0 flame rated. These properties lend themselves to cushioning and padding for electronics or dust gaskets. LCD gaskets or touch screen gasket are common applications due to the very low rebound force. Like the vast majority of materials carried by Stockwell, pressure sensitive adhesives (PSA, both acrylic and silicone adhesives) can be applied to one or both sides of the foam.

Also in our Liquid Silicone Foam product line are:

BF-1000 is an Extra Soft Silicone Foam with an open cell structure

HT-870 is a Soft Silicone Foam with an open cell structure

HT-800 is a Medium Silicone Foam with a modified closed cell structure

HT-820 is a Firm Silicone Foam with a modified closed cell structure

HT-840 is an Extra Firm Silicone Foam with a modified closed cell structure

F-12 is similar to BF-1000 except with a fabric finish on one side and slightly courser cell structure

All the above silicon foam products listed are UL94 V0 listed (see specific datasheet for details). For more information on BF-2000 Ultra Soft Silicone Foam or other products offered by Stockwell Elastomerics please contact us at (215) 335-3005 or service@stockwell.com.

Large Gasket Splicing and UV Corner Bonded Gaskets

2008-12-03T10:03:00.002-05:00

Stockwell offers UV corner bonding for large gaskets. This process includes die cutting or water jet cutting the gasket “legs” with a dovetail type joint at the ends. The jointed ends are then bonded with a UV sensitive adhesive. The bonding is a manual process; therefore a cost analysis is required to determine whether the material savings exceeds the added labor of the bonding process. The material type, material thickness, overall size and order quantity are determining factors as to whether corner bonding is cost effective.

The most common gaskets using UV corner bonding are large NEMA 4 gaskets used in Telecom applications. These are large silicone gaskets with PSA backing (pressure sensitive adhesive backed gasket) used outdoors. Silicone offers excellent UV and ozone resistance and maintains its mechanical properties in very cold and hot conditions. The corner bond maintains a seal under hose down conditions where un-bonded gaskets generally leak. It is important to understand enclosure design along with proper gasket material selection is paramount to successful NEMA enclosure seal.

For more information about corner bonding or other gasket applications, please contact Stockwell at (215) 335-3005 or visit our website at stockwell.com.

Why Stockwell is a Sensible Strategic Partner in this Rough Economy

2008-10-27T17:13:00.007-04:00

Stockwell Elastomerics’ business model has been centered around low to mid volume runs, quality and speed. For companies practicing Lean Manufacturing this business model makes good sense. Stockwell maintains stock in its core product lines such as Silicone Foams, Silicone Sponge, Solid Silicone, Poron, Thermal products, EMI gasketing materials, and Pressure Sensitive Adhesives (PSA). This stock along with quick changeovers and semi-automated production equipment (Die Cutting, Water Jet Cutting, Slitting and Laminating) allows for fast turns on low to mid-volume runs.

In the current economic climate, overproduction and inventory are much more of a liability than they were a year ago. With some customers relying on lines of credit and banks being more cautious, the risk of orders being cancelled and OEM’s being left holding the bag is much greater. Having a fast turn supplier such as Stockwell who can run smaller batch sizes and still meet long term production needs with scheduled releases allows OEM’s to have less “skin in the game”.

For more information on how Stockwell can meet your production needs, please contact us at 215-335-3005, service@stockwell.com or visit our website http://www.stockwell.com/.

THICK EMI GASKET & EMI GASKET OPTIONS

2008-08-19T17:19:00.009-04:00

Stockwell Elastomerics provides custom EMI gaskets regularly for a wide range of customers. Each application is a bit different; some can be cut from “off the shelf” sheets of nickel graphite filled silicone and others may require special fluorosilicone compounds or silver plated particle filled silicone for more conductivity. Generally materials are .062” thick or thinner with a few conductive compounds available up to .125” thick. So what are the options for thicker EMI / NEMA seals? Below are a few pros and cons for different manufacturing techniques for EMI gaskets.

Option 1 – Mold the Gasket
Pros: You can control your design; sealing beads and 3 dimensional shapes are possible. Material savings; EMI compounds cost more that unfilled non-conductive compounds. Compression molding minimizes raw material waste.
Cons: Molds are more costly than tools used in die cutting, and molded parts have longer production lead times than die cut or water jet cut gaskets.

Option 2 – Mold Sheets and Water Jet Cut
Pros: If a part is smaller or there is little center waste, molding sheets from a standard sheet mold and then waterjet cutting the part geometry may be most feasible. This option offers flexibility in material thickness (.020” to .500”), conductive adhesive backings, and there is no tooling charge for the waterjet cutting process if a CAD file is provided. Lead times for this option are relatively short based on using our in-house 12” x 12” sheet tooling.
Cons: Geometries are limited to 2 dimensions and there is some edge and center waste.

Option 3 – Non-conductive sponge or foam with a bonded conductive wire mesh
Pros: This option offers another range of flexibility. Stockwell uses its core silicone foams and silicone sponge products (with or without adhesive backing) and bonds a Monel (Nickel/Copper alloy) wire mesh to the inside or outside edge of a gasket. This option offers lower compression forces, UL94 V0 foam option, closed cell sponges and a variety of thicknesses cut from standard, readily available roll or sheet stocks. Waste is less costly due to the non-conductive and expanded polymer. Lead time for smaller or initial volumes is relatively quick.
Cons: Geometries are limited to 2 dimensions. There is some assembly which may require scheduled shipments. Heavy compression and release cycles may disturb the mesh to polymer bond.

For more information about EMI gaskets, custom EMI gasket, silicone gaskets or other Stockwell products call 215-335-3005, email service@stockwell.com or visit our website at stockwell.com.

Gasket Compression Pecentage Calculation

2008-07-08T08:38:00.010-04:00

720 lb Clamp, Foot Print / Contact Area Foot Size: 3" x 12" each
Total Area: 2 x 36in² = 72 in²

HT-800 Silicone Pad Size: 3" x 12" each
Total Area: 2 x 36in² = 72 in²

Mounting Plate

Calculation: Load / Area = 720lb / 72 in² = 10 lb/in²

Compression: From the Compression Force Deflection Curve, HT-800 will compress approximately 30%. (Note, compressing more than 50% may rupture cells and damage material)

For more information or applications assistance, please contact Stockwell Elastomerics (215-335-3005 or service@stockwell.com

Acrylic Adhesive Backed Silicone Gaskets

2008-06-03T13:49:00.002-04:00

Is Silicone PSA required for silicone material?
We often see silicone based adhesive specified with silicone materials. Silicone adhesives are expensive as compared to acrylic adhesives, in some cases more than 5 times the cost of acrylics. Silicone PSA’s bond strength is not as good as acrylics and there are limited offerings. So why are silicone adhesives being specified? Silicone adhesives can be adhered to silicone material without surface preparation. Many fabricators do not have the technology to apply acrylics to silicone materials, however Stockwell has been doing it for years.

When should silicone adhesives be specified?
Silicone adhesives do have their niche, they are great for very low and high temperature extremes where acrylics and rubber based adhesive lose their efficacy.

Having a Pressure Sensitive Adhesive (PSA) backing on gaskets is not required to make a good seal but is often recommended to aid in assembly. The added cost of the adhesive is offset quickly with the time saved during assembly.

For more information about materials contact visit Stockwell Elastomerics at stockwell.com or call 215-335-3005.

UMPC (Ultra Mobile Personal Computer), Ruggedizing Components - Overview

2008-05-21T14:27:00.008-04:00

There is a new breed of personal computers on the market today, the Ultra Mobile PC. One of the obvious driving sectors for these products is the military where sensitive electronics are exposed to harsh environments. These UMPC’s or ultra rugged computers have also been used commercially in a limited capacity but with the mobile device market on a steep incline, consumers are demanding a greater level of protection for their mobile devices.

In January of 2000 the DoD released standard MIL-STD-810F which is a very comprehensive guide for Environmental Engineering Considerations and Laboratory Testing Procedures. This covers temperature, vibration, shock, EMI shielding, fluid contamination, etc…

Stockwell has been “Ruggedizing” electronics for many years. The key to achieving a truly rugged component is in the materials. For example, if a device is exposed to extreme low temperature and dropped it will rely on the cushioning pad for protection. Traditional “rubber” will firm up and pass the energy on to the internal components, ultimately leading to a device failure. A silicone foam product is a good choice for mechanical shock and vibration in extreme temperatures, silicone maintains cushioning properties below -80°F. Where fuel and chemicals may make contact with the elastomeric cushion, a closed cell fluorosilicone sponge might be the better choice.

Stockwell has a wide range of materials to meet the most demanding ruggedizing requirements, including; chemical resistant, soft sponges and foams for cushioning and damping, EMI shielding materials, open cell and closed cell products for dust and water sealing. Production capabilities include custom molding, fast-turn water jet cutting, die cutting and adhesive laminations.

High Performance Acrylic Adhesives on Silicone

2008-04-09T20:23:00.002-04:00

In recent months we have seen more requirements for Silicone Foam and Closed Cell Silicone Sponge Enclosure Gaskets and Cushioning Pads requiring high strength pressure sensitive acrylic adhesives for bonding to powder coated metal surfaces and certain low surface energy plastics.

Secure lamination of acrylic pressure sensitive adhesives onto silicone rubber is not possible without priming the silicone rubber. Stockwell has developed primers that allow for lamination of 3M Corporations’ 9485 acrylic transfer film adhesive and 9490LE film supported acrylic adhesive onto silicone foam, closed cell silicone sponge and solid silicone rubber.

3M 9485 acrylic adhesive is .005” thick unsupported transfer film adhesive. Its ultimate bonding strength on stainless steel is 150 lbs / inch of width. 9485 withstands high temperature excursions for brief periods up to 400°F, and long term temperatures up to 300°F continuous without slumping or shearing. This adhesive is well suited for thick silicone sponge gaskets on most metal surfaces. Unsupported transfer film adhesives allow for bonding to contoured surfaces and permit forming corner radii using strips of gasketing.

3M 9490LE acrylic adhesive is .0067” thick film supported adhesive. This adhesive is formulated for secure bonding to most surfaces, including many low surface energy plastics and powder coated metal surfaces. 9490LE withstands high temperature excursions for brief periods up to 300°F, and long term temperatures up to 200°F. Film supported adhesive backings provide dimensional stability, which may benefit the assembly of thin-walled gaskets onto some enclosure designs.

Rubber? - Rubber Gasket, Rubber Seals, Rubber Pads…

2008-03-17T13:51:00.004-04:00

It is interesting how the word “rubber”, which historically has referred to Natural Rubber (also known as isoprene) has become a general term for elastomeric materials. Natural rubber is the original elastomer; however, over the years there have been many more synthetic polymers developed, each with its own unique property.

From an engineering standpoint it is important to know the demands and environmental conditions to which a “rubber” component will be exposed. Many of us have seen a black, flaking, cracking gasket essentially at a failure state. For a critical water seal the cracking could allow leaks causing damage to expensive electronics. For pads, excessive compression set (when the elastomer fails to rebound) may be the mode of failure, ultimately transferring mechanical shock or vibration to the device. Many of these common failures can be avoided with proper material selection. Temperature, UV, ozone, and chemicals all play a role in how well a “rubber” part will survive. Stockwell helps customers with material selection and in most cases will provide samples at no charge for testing.

For more information about materials contact visit Stockwell Elastomerics at stockwell.com or call 215-335-3005

Adhesive Backed Gasket

2008-01-24T09:34:00.000-05:00

For decades Stockwell has been applying pressure sensitive adhesive backings onto gasketing materials. Adhesive backed gaskets are very appealing to our customers for several reasons. More often engineers and designers are specifying adhesive backings for gaskets. A peel and stick gasket (or peel and stick vibration pad) offers some nice features that plain or non-adhesive backed gaskets don’t have, below is a list of a few. (Link: Stockwell adhesive offerings)

Ease of installation – a peel and stick gasket allows operators and assembly technicians to install a gasket or pad quickly and easily. The time saved by having an adhesive backing justifies the additional cost.

Gasket Positioning – when an adhesive backed gasket is installed and “stuck” in place it stays in place when the lid or mating surfaces are compressed. Without being fixed in place the motion of the mating faces could move or twist the gasket cause a leakage.

Kiss-cutting - adhesive backed gaskets are able to be kiss-cut (see blog posting Oct. 12, 2007). Manufacturing engineers like this because parts are presented to the operators on neat roll and parts are removed from the liner versus individual parts requiring tedious liner removal

Bolt hole position – a supported adhesive backing or double coated adhesive (see blog posting July 30, 2007) gives a gasket that has a series of bolt holes dimensional stability. Essentially the thin P.E.T. layer does not let the gasket stretch in the X and Y dimensions. Without this support layer the gasket may stretch during installation and the holes will not line up.

Stockwell offers a wide range of adhesive backed gaskets. Adhesive backings are applied to the vast majority of materials. These include Poron urethane foam, silicone foam, silicone sponge, solid silicone, Neoprene sponge, electrically conductive gasket materials, thermal pads to name a few. Adhesives such as 3M’s Low Surface Energy (LSE) adhesives, transfer adhesives, double coated (or supported adhesives), thermally conductive adhesives and electrically conductive adhesives are available.

Stockwell is not limited to applying silicone adhesive to silicone rubber. With several proprietary processes, Stockwell is capable of bonding a wide range of quality adhesives including acrylics and silicones. (Stockwell adhesive offerings)

For more information regarding adhesive backed gaskets, grades of adhesive, peel and stick or adhesive offerings, please contact us at service@stockwell.com or 215-335-3005.

New Stockwell Brochure!

2008-01-09T11:28:00.001-05:00

Over the last few months Bill Stockwell has been working on a new brochure that highlights Stockwell Elastomerics core products and service. I thought it would be interesting to show a couple pages from an archive brochure. I’m guessing this brochure is from the 1940 – 1950’s. Think about what may have been involved with that brochure. No digital pictures or computers back then!

It’s remarkable how some things remain the same and others do not. As an example on the inside cover of the 1940ish brochure the slogan reads “What we really SELL is SERVICE” this very much holds true for Stockwell today. The old Stockwell Rubber Company sold everything “rubber” whereas today Stockwell Elastomerics is focused on high performance materials (such as silicone, Poron urethane foam, thermal and electrically conductive rubber), custom manufacturing (waterjet cutting, die cutting, slitting, and molding. Quick reliable service is still at the core of Stockwell's business model.

The New 2008 Stockwell Elastomerics Brochure:

For a copy of our New Brochure or more information on our products and services, please contact us at service@stockwell.com or by phone at 215-335-3005.

Large Custom Gaskets

2008-01-02T09:33:00.000-05:00

Every so often we receive inquiries for large custom gasket. In some case they are extreme such as the one shown below. In many cases they are for NEMA enclosures (commonly NEMA 4). A single piece gasket generally offers the best seal, however many gaskets exceed the width of the material. In this case a jointed corner may be an option.

Single Piece - a single piece gasket will offer consistent deflection force around the gasket. The con to a large single piece gasket is the center waste. If engineer are making multiple gaskets they can create an assembly level drawing that show several gaskets nested.

Joint and Bond – when a single piece is required but the gasket dimensions exceed the material dimensions, a jointed and bonded gasket may be an option. In most cases this is a die or water jet cut male/female dove tail that is then UV bonded. This type of gasket needs to be evaluated to see that the extra labor of bonding does not exceed the material savings. Also, for foams and sponges the corners will be firmer than the gasket material.

Joint (no bonding) – similar to the Jointed and Bonded gasket, a male/female dove tail is die or water jet cut. In this case the gasket is provided in 4 pieces and is mated during installation. In some cases a bond is never required. This is most dependant on the enclosure configuration and the level of sealing required.

Materials most commonly used for large custom gaskets are silicone foam and silicone sponge. Since the sealing area is relatively large (i.e. square inches) the soft nature of these materials allow for lower closure forces to get proper deflection for sealing.

For more information please feel free to contact us at service@stockwell.com or 215-335-3005.

Silicone Gasket

2007-10-29T14:20:00.000-04:00

Stockwell carries a wide range of materials so that we can meet the demands of most application. Over the years silicone has grown to be our core product. We are seeing more and more engineers specifying silicone products into their design because of its unique properties. Today Stockwell keeps in stock sheet good materials and compounds for custom molded silicone parts.

Key properties:
• High Operating Temperature
• Low Operating Temperature
• UV resistant
• Ozone resistant
• Excellent compression set resistance (rebound)

Silicone offerings include:
• Silicone Foam - that is UL94 V0 rated, excellent for electrical enclosure
• Closed Cell Silicone Sponge - for soft water gaskets such as IP 66, IP 67, and NEMA 4
• Solid Silicone – for water tight seals where higher closure forces are available
• Custom Molded Silicone – standard 20 durometer thru 70 durometer
• Electrically Conductive Silicone – for EMI and ESD gaskets
• Thermally Conductive – for gap pads and press pads for thermal management
• Adhesive Backed Silicone – Stockwell applies pressure sensitive adhesives (acrylic and silicone) to most materials in stock

For more information regarding silicone gaskets or other product offerings, please contact Stockwell at service@stockwell.com or call 215-335-3005.

What is kiss cutting and a kiss cut gasket?

2007-10-12T14:33:00.000-04:00

Kiss cutting is a die cutting process where a gasket or pad is supplied rolled up on the adhesive liner. If you were able to watch the cutting process in slow motion you would see the die penetrate the gasket or pad material, then continue through the thin adhesive layer and cut partially into the adhesive liner. The gasket or pad must have a Pressure Sensitive Adhesive (PSA or “peel and stick”) backing for kiss-cutting to be possible.

Kiss cutting has several advantages over individually cut through parts. Kiss-cut gaskets the parts to be rolled up, parts on rolls are easier to handle can and can be set up neatly and dispensed in a paper towel like fashion at assembly work stations. Also, peeling the part off the release liner is considerably easier than removing the release liner from an individual part, this helps increase production throughput.

Stockwell regularly kiss-cuts gaskets and pads from solid silicone, silicone sponge, silicone foam, and Poron. Other materials include foam adhesives such as 3M VHB’s and thermal pads. Note, not all materials and parts can be kiss-cut, for more information please contact service@stockwell.com .

Pressure Sensitive Adhesive. Supported Construction

2007-07-30T08:55:00.000-04:00

Supported adhesives, also called double coated tapes, get their name from their construction. A thin plastic like layer (typically P.E.T.) is coated on both sides with a thin layers of adhesive. The most common family of Pressure Sensitive Adhesives are acrylic based. Adhesive manufacturers such as 3M, Adchem, and St. Gobain offer many varieties of adhesives with different bond strengths, temperature ranges, and mechanical properties. The thin support layer (or carrier layer) of supported (or double coated) adhesives offers dimensional stability when added to an elastomeric material.

These pressure sensitive adhesives (PSA) are typically self wound. When unrolled one side of the adhesive is exposed. In most cases Stockwell applies the exposed adhesive to the gasket or pad material, the release liner remains in tack until the end user is ready to peel and stick. This adhesive backing is very helpful for the end user during assembly. In some cases we will apply a second liner to the exposed face and die cut the adhesive to a specific geometry.

For more information on Pressure Sensitive Adhesive, please follow the link to our website http://stockwell.com/pages/materials_adhesives.php or contact us at service@stockwell.com.

Clear or Transparent Silicone Rubber

2007-07-17T16:44:00.001-04:00

Although we usually think of silicone rubber as being pigmented red, black, or gray in color, it is also available in clear, transparent sheets and as custom molded parts.
Using our liquid injection molding (LIM) capability we can mold clear components in durometers from 10 to 70 Shore A.
For flat gaskets we suggest HT-6240, a clear, high purity, 40 durometer silicone rubber which we inventory in 36” wide rolls in .010”, .020”, .032”, .062”, and .125” thicknesses. HT-6240 is stored between two liners to maintain cleanliness.
A pressure sensitive acrylic or silicone adhesive can be applied to HT-6240. As with our other silicone rubber and sponge products Stockwell can supply a sample sheet or a prototype part cut on our water jet. For a data sheet on HT-6240 use the following link:
www.stockwell.com/pages/solid_silicone.php

Transparent silicone can be used as an “invisible” gasket to enhance cosmetic appeal. Other uses include overlays, flexible laboratory covers, transparent membranes, and air flow diaphragms on respirators and ventilators.

Waterjet Cut Gaskets

2007-04-23T18:17:00.000-04:00

The picture below is a demonstration piece that I made to show how Stockwell's 3 waterjet units are able to cut complex geometries with ease. A steel ruled tool or solid steel tool would be relatively expensive and still would not offer tolerances equal to the waterjet cut parts. As a service to our customers, Stockwell Elastomerics will waive the programming setup charges if a CAD file is provided.

The piece shown above was cut from fluorosilicone sponge that meets the AMS-3323 requirements. Fluorosilicone is most commonly used in the aerospace industry when chemical resistance is required in conjunction with good mechanical properties at low and high temperatures.

We are often water jet cutting varieties of silicone gaskets and silicone pads including; solid silicone, silicone sponge, and silicone foam. Aside from silicone products, we are able to water jet cut the vast majority of our stock. Stockwell has hundreds of materials such as; urethane foam, thermal gap fillers, emi / esd material, high grade nitrile, EPDM sponge, just to name a few. In many cases using the water jet can offer cost savings especially with more costly materials such as conductive silver filled fluorosilicone where better yields are possible.

For more information on waterjet cut gaskets, please contact us at service@stockwell.com

Sponge EPDM Gasket

2007-01-22T10:54:00.000-05:00

Recently I’ve been seeing more applications where EPDM gaskets, in particular closed cell EPDM sponge, are the best value for a given situation.

EPDM (Ethylene, Propylene, Diene, Methylene) is commonly specified for outdoor gasketing applications. This is due to EPDM's excellent weather ability, and specifically its resistance to UV, Ozone and Oxidation. The closed cell structure minimizes water absorption which makes it a good material for enclosure gaskets needing occasional resistance to moisture and indirect water spray. EPDM sponges are available in various firmnesses from very soft to firm. EPDM gaskets are not recommended where they may come in contact petroleum based oils and certain chemical (call for specific information).

For critical long term weather sealing and wind-driven rain, silicone gaskets made from silicone sponge or closed cell silicone foam may be necessary. But when the budget gets tight, you may want to consider closed cell EPDM sponge as an option.

To get more information about custom EPDM gaskets, please contacts us at service@stockwell.com.

Electrically Conductive Coated Pads for ESD Protection

2006-12-13T11:13:00.000-05:00

Stockwell has a proprietary coating process that allows us to make custom electrically conductive silicone pads for ESD protection. The conductive pads are available in various thickness, firmnesses and geometries. The coated silicone sponge allows for a wide temperature range without loosing physical performance. The coating creates a conductive path on the surface of the material, parts can be partially or entirely coated to best suit the application. These pads are commonly used, but not limited to, the IC handling industry. The surface resistivity of the conductive coating is 20,000 Ohm-in² per ASTM D257. For more information please visit our ESD EMI materials web page or contact us at service@stockwell.com

Thermally Conductive Fluorosilicone

2006-10-24T16:46:00.000-04:00

Thermally Conductive Gap Pads or Gap Filler Pads provided for electronic thermal management have nearly always been fabricated from Silicone Rubber ased materials.

One of our customers in the aerospace electronics industry reported their design required thermal interface pads – however the pads had to resist the effects of coolants and fuels – which tend to severely swell and degrade silicone rubber based materials. The usual silicone based Gap Pads would break down and likely contaminate the system.

Our representative, Tom Jeffords, suggested that our customer evaluate a 60 durometer, nickel-graphite filled fluorosilicone material. Nickel-Graphite based fluorosilicone rubber is normally be used for electrically conductive EMI Shielding Gaskets that require fluid resistance. However, we had the material tested for thermal properties and learned that our SNEF-60 has a Thermal Conductivity of 0.5 W/mK. Although the 60 durometer Shore A hardness is firmer than most of our Gap Pad materials, our customer was able to incorporate enough compression in their hardware design to provide adequate contact on the nickel-graphite filled thermal pads.

Subsequently, we also had our SCF-444, 45 durometer silver plated aluminum filled fluorosilicone tested for thermal properties - and the results were a Thermal Conductivity of 1.2 W/mK.

I remind myself that we are continuing to evolve from a rubber fabricating company to a materials technology company. It’s all about the materials.

P.S. – St. Gobain Performance Plastics group performed the thermal testing, even though the material tested was not theirs. Kudos to their technical service group for their assistance!

2006-09-11T15:06:00.000-04:00

NEMA and IP Specifications Help Define Enclosure Gaskets

“Enclosure gasket” is a broad term that basically describes the gasket between a housing and a cover or door on the housing. The configuration and function of the enclosure can vary drastically, from metal to plastic, large to small, dustproof to waterproof , etc. NEMA and IEC International Protection (IP) standards help engineers define the specific requirements that need to be met for their design. As an example, a designer of an outdoors telecommunications base-station housing may call out IP65 or even more aggressive IP66. This tells the gasket designer that the gasket needs to be dust proof and water tight under hose down conditions (NEMA call out for this would be NEMA 3 or NEMA 4).

It is critical to specify the correct gasketing material. If a gasket fails; hundreds or thousands of dollar worth of sensitive electronics can be damaged. Items to consider are environmental conditions (indoor, outdoor); exposure to water, chemicals, oil, sun light (UV), etc… The general performance function required such as dust sealing, wash-down protection, or submersion will also determine the best material for the enclosure. For assistance with material selection contact Stockwell Elastomerics (215-335-3005 or service@stockwell.com).