The Elastomerics Blog

This blog has moved

2010-04-23T18:42:00.001-04:00

This blog is now located at http://elastomerics-blog.stockwell.com/.
You will be automatically redirected in 30 seconds, or you may click here.

For feed subscribers, please update your feed subscriptions to
http://elastomerics-blog.stockwell.com/feeds/posts/default.

Wind Turbine Blade - Transportation Cushioning Pad

2010-03-08T20:41:00.010-05:00

Cast liquid silicone rubber sheet materials have the tendency to grip smooth surfaces - especially table tops and similar work surfaces.

Stockwell Elastomerics has been working with a major Wind Turbine Blade manufacturer on a design and logistics challenge - how to hold and transport fragile wind turbine blades that are 110 feet long and greater - without squeezing the blade too firmly. Wind Turbine Blade damage can be an expensive problem, not just from the cost to repair the blade, but also from downtime and installment delays in bringing the units on-line.

After several iterations, we developed a combination of closed cell silicone sponge cushioning with a 'grippy' liquid silicone rubber coated fiberglass cloth surface lamination.
The result has been a soft holding pad with enough tensile strength to cradle the blade as it is transported to the installation site. We have been told the blade damage has been reduced by 40% when our transportation cushion pads are used.

Closed cell silicone sponge was selected for the cushioning layer due to its low compression set and age, sunlight and weather resistance in prolonged outdoor conditions. The closed cell silicone sponge can be laminated to virtually any thickness using silicone based bonding adhesives. Closed cell silicone sponge is available in 3 grades of firmness - soft, medium and firm. The grippy LSR coated fiberglass has the same inherent age resistance - making this laminated construction a great example of how Stockwell Elastomerics can develop a combination of properties to solve an engineering challenge.

UL94 V0 Flame Retardant Silicone Sponge Rubber

2010-02-02T12:44:00.006-05:00

St. Gobain’s R-10400-M flame retardant silicone sponge is a unique expanded silicone sheet product. It has similar mechanical properties as standard silicone sponge rubber but with flame resistance, R-10400 holds an aggressive UL94 V0 flame rating. Silicone is a naturally heat resistant rubber, however without enhanced chemistry it is capable of burning in the presence of a flame. R-10400 may be used similarly to standard silicone sponge products such as enclosure gaskets, soft gasket, vibration dampening, environmental gaskets, and water sealing but also for application such as military and electronics that require a UL94 V0 flame rating or flame resistance.

Description: Flame Resistant Closed Cell Silicone Sponge Rubber
Put up: Silicone Roll or Silicone Sheet
Temperature Range: 100 – 500°F (-73 – 260°C)
Force Deflection: 10psi (@ room temp)
Compression Set: 10% (22hrs @ 212°F)
Thermal: Thermal Insulator, .02 W/m-K
Electrical: Electrical Insulator, Volume Resistivity 8E15 Ohm-cm
Flame Rating: Flame Retardant Rubber, UL94 V0
FDA Rated: 21 CFR 177.2600

Other properties such as UV resistant and a wide functional temperature range, makes R-10400 an ideal product for outdoor gasket and electronic enclosure gasket applications, where performance is paramount. Stockwell offers a wide range of adhesive backings (peel and stick) for ease of installation.

For more information on R-10400 flame resistant silicone sponge or other UL94 flame rated products, please call (215) 335-3005 or email service@stockwell.com.

Conductive Pad, ESD Pad, Conductive Adhesive – Cryogenic Exposure

2010-01-08T14:19:00.003-05:00

SE65 is a carbon filled electrically conductive silicone rubber with a durometer of 65 on the Shore “A” scale. SE65 is typically used to dissipate or more specifically ground out static while providing some compliance and cushion. SE65 can be bonded to a conductive surface (aluminum or steel) using Stockwell’s RTV-60-CON which is also a carbon filled silicone based RTV (Room Temperature Vulcanizing). Bonding SE65 with RTV-CON makes a very intimate and strong bond when the surfaces are prepared properly.

Silicone has a general operating temperature ranging from -100 to 500°F (some grades vary). The SE65 has a conservative rating of -65 to 400°F. As a very crude test to see if there would be any deterioration of the SE65, RTV-60-CON or the bond between surfaces, a test piece bonded to aluminum was run thru Stockwell’s cryogenic deflasher, removed and hit with a hammer. The attached video clip shows the machine in idle mode set to -80°F (run mode). The sample was tumbled at -80°F for 60 seconds, removed and hit. There was no indication of bond or material degradation. This was a very crude test but does offer some insight to how well the bond holds up.

Stockwell Elastomerics carries a comprehensive line of ESD and EMI conductive silicone sheets, roll goods and molding compounds. For more information about these products, please call 215-335-3005 or email at service@stockwell.com.

Silicone Materials Selection Guide Updated

2009-12-21T09:37:00.005-05:00

Stockwell Elastomerics updated Silicone Materials Selection Guide - a comprehensive guide offering insight on the properties and benefits of using silicone for gasketing, sealing, and cushioning applications. This guide details Stockwell Elastomerics’ silicone rubber materials offerings in closed cell silicone sponge, cast silicone foams, gum based solid silicone and liquid based solid silicone. In addition, many common pressure sensitive adhesives offerings and product-enhancing surface lamination options for silicone foam and silicone sponge rubber are listed. This updated Silicone Materials Selection Guide is a quick “go-to” reference for engineers and designers. Silicone has become the material of choice by engineers for critical gasketing and cushioning applications. This can be attributed to its wide operating temperature range, resistance to compression set (good memory), UV resistance and long life.

Stockwell Elastomerics offers fast-turn prototyping for most silicone materials, often utilizing its extensive water jet cutting capabilities to produce cut to size parts from customer supplied CAD files.

To Request a Copy of the Silicone Materials Selection Guide
Download it directly from http://www.Stockwell.com/SiliconeGuide or contact Stockwell Elastomerics by phone (215) 335-3005 or email service@stockwell.com to request a printed copy.

Stockwell Elastomerics’ core competence is the fabrication and molding of silicone rubber and similar high performance elastomeric materials. Stockwell’s in-house capabilities include water jet cutting, custom molding, die cutting, and adhesive lamination. For more information on Stockwell Elastomerics’ offerings in silicone rubber, silicone sheet, molding and fabrication capabilities call (215-335-3005) or email service@stockwell.com.

Gasket Tape, Strip Gasket & Strip-N-Stick

2009-11-03T10:00:00.005-05:00

Gasket Tape, Strip Gasket and Strip-N-Stick™ are common names for a strip of gasket material with peel and stick adhesive backing. Gasket tape is supplied on a roll and widths can be cut as needed, typically 0.5” to 3”. Strip gasket is good for dust and light pressure water seals such as NEMA3, IP61, IP62. It should be noted that closed cell foam, closed cell sponge or solid materials should be used in water sealing applications and the enclosure should not allow water pool on the gasket. For aggressive water seals such as NEMA 4, NEMA 4X, IP65 & IP66, enclosure design, material selection, and gasket joints play a greater roll in enclosure sealing.

Gasket tape materials can vary from open cell urethane foams such as Poron, closed cell silicone sponge such as R-10470 & R-10480 and even solid rubber materials can be provided in Strip Gasket form. Various adhesive backings are also readily available, most common are acrylics but rubber and silicone adhesives are also available. Gasket tape is available in standard configurations such as the Saint Gobain’s Strip-N-Stick™ silicone sponge and silicone foam tape products. Stockwell can also apply any variety of 3M or Adchem adhesive to Poron foam, Neoprene sponge, Bisco silicone foams and slit strips (Gasket tape) as needed.

For more information on Gasket tape and strip gaskets, visit http://www.stockwell.com/, call 215-335-3005 or email service@stockwell.com.

Steel Rule Die for Custom Gasket Cutting

2009-10-26T17:24:00.002-04:00

Often when people hear “custom” and think high cost; special setup charges, and tooling charges. In reality custom gaskets can be custom made for relatively low cost. If volumes warrant die cutting (often 500+ pcs) a steel rule tool can be made. A die for a six inch square window gasket with fastener holes at each corner can be made for less than $200. When amortized over a few thousand pieces, tooling cost quickly become pennies/per part.

Steel ruled dies are often made by accurately laser burning the part geometry into engineered, dimensionally stable plywood. Then a long steel blade (almost like a razor blade) is precisely bent and press fitted into the wood. Holes are made by pressing punch sets into the plywood. Tools in the 12” x 12” range can hold a tolerance of less that .012”.

Stockwell uses steel rule dies to cut Poron urethane foam, silicone foam, silicone sponge, and neoprene sponge. It is important to know that softer and thicker foam or sponges tend to have wider tolerances because the material compresses before it is cut through. Solid silicone gaskets, thermal gasket, emi gaskets can also be cut with steel rule dies.

Gaskets and pads can be made many ways. Stockwell takes into consideration gasket material type, gasket thickness and quantity to determine the production method that is most cost effective. Very tight tolerance gaskets or low volume gaskets can be waterjet cut with no tooling charge.

For more information about gaskets or gasket materials cut with steel rule dies, visit http://www.stockwell.com/ or call 215-335-3005.

Formex – Thin UL Rated Polypropylene Sheet

2009-10-13T14:17:00.004-04:00

Formex GK polypropylene sheet has been engineered to meet electronic equipment requirements. Formex has a high dielectric strength making it a good electrical insulator, does not absorb moisture and is UL listed carrying a UL94 V0 or VTM-0 flame rating.

Over the last few years Stockwell has been laminating Formex to other UL94 rated materials such as HT-800 & BF-1000 silicone foams. Laminations are most often used as either a stiffening layer or as a protective top layer. An example of a stiffening layer would be a thin wall dust gaskets that is flimsy. Adding a thin layer of Fomex between the adhesive layer and rubber creates a stiffening effect which aids in assembly. An example of a protective layer would be a battery pads that will see wearing from installation and removal of the battery. In this case, a layer of Formex polypropylene is bonded to the top of the pad.

Stockwell carries thin grades of Formex, which are available for direct die cut parts, waterjet cutting (may have frayed edges) or as a lamination. Laminations to Poron foam or silicone foam are most common. Pressure Sensitive Adhesive (PSA) backing is also available. For more information regarding Formex polypropylene and other UL rated materials stocked and converted by Stockwell Elastomerics visit http://www.stockwell.com/ or call (215) 335-3005.

Rubber Temperature Range

2009-09-22T13:15:00.003-04:00

Whether you are designing a pad or gasket it is important to know how the environment will affect your part. In most cases, pad and gasket are dynamic in their operation. As an example a door gasket on a NEMA enclosure will compress and rebound as the enclosure heats up and cools off due to thermal expansion. If the gasket loses its ability to rebound (i.e. takes a compression set) or even worse brakes down, the seal could be lost leading damage or system failure.

Excessive heat can be linked to many gasket failures in the form of compression set. I recently saw a sprinkler control enclosure that used a sponge cord (likely a chloroprene blend) that took a major compression set. This set made the gasket virtually useless. In a wind driven rain situation, there would be ingress of water. Luckily this box was mounted inside a garage. It is important to know that elevated temperatures can encourage compression set. ASTM has tests for sponges and foams at 2 different temperatures 158°F & 212°F.

Catastrophic failure of a gasket or pad can also be attributed to exceeding the operational temperature of the “rubber”. Below is a list of materials and their general operating temperature ranges. Note, refer to specific manufactures datasheet before selecting a material.

General Operating Temperatures for Common Materials*
Urethane: less than 250°F (121°C)

Natural Rubber: less than 250°F (121°C)

Chloroprene (Neoprene): less than 300°F (149°C)

Nitrile (Buna-N): less than 300°F (149°C)

EPDM: less than 400°F (204°C)

Fluorosilicone: 400 – 500°F (204 – 260°C)

Fluorocarbon: 400 – 500°F (204 – 260°C)

Silicone: 400 – 500°F (204 – 260°C)
*Temperatures are general, values will vary with grade. Refer to specific specifications for actual product temperature ratings.

For more information about gasket and pad materials such as solid silicone, silicone sponge, silicone foam, fluorosilicone sponge, Neoprene, EPDM, Nitrile, Poron urethane foams or other gasket materials, please contact Stockwell at (215) 335-3005 or visit our website at www.stockwell.com.

Silicone Foam - Waterjet Cut & Foam Assembly

2009-08-28T14:36:00.005-04:00

One of the more interesting silicone foam parts Stockwell has made was a thermal insulating jacket for an electronic device. The material used was HT-800 silicone foam, the foam’s cellular structure gives the material insulating properties. HT800 is a UL94 V0 flame rated foam and also has electrically insulating properties.

The part shown below was constructed from standard “off the shelf” thicknesses of HT-800, though a few thicker layers required laminating. A variety of shapes were waterjet cut and hand assembled.

Stockwell has a dedicated Production Cell for Assembly where silicone foam, silicone sponge, urethane foam and EMI materials are bonded, lamininated and/or assembled. For more information on Stockwell Elastomerics assembly capabilities other silicone rubber, closed cell sponge, & Poron applications, please contact Stockwell at (215) 335-3005 or visit our website at stockwell.com.

Platinum Cure Silicone versus Peroxide Cure Silicone

2009-08-20T09:42:00.006-04:00

Addition or platinum cured silicone rubber offers an increasingly popular alternative to conventional peroxide cure silicone products – especially for healthcare applications which require the utmost purity and cleanliness of materials. The name “addition cure” derives from the vulcanization reaction which consists of a multi-functional silicon hydride cross-linker, which in the presence of a precious metal catalyst such as platinum, cures with a longer cross-link chain for added tensile strength and flexing capability over peroxide cured silicones.

Conventional peroxide cure silicones – dimethyl polysiloxane and methylvinyl polysiloxane – comprise majority of the gum base molded and rotocured silicone rubber sheet on the commercial market. A by-product of the heat curing process can be a white crystalline powder diffusing to the surface known as bloom. To prevent future reversion of the rubber and meet general healthcare requirements, post-baking for 2 to 4 hours in a hot air circulating oven from 400°F to 480°F is recommended. Our preferred silicone sheet manufacturers post bake the roto-cured sheets of silicone as a standard practice. The post baking or post curing process will generally improve the compression set performance of peroxide cured silicone rubber. Silicone sheets without a post-cure will often have a sweet, distinctive odor – which may be dichlorobenzoyl peroxide. A post bake will drive off this odor.

The liquid silicone rubber (LSR) compounds we injection mold are Platinum Cure Silicones. They are provided to us in pails or drums of Part A and Part B. The Part A contains the catalyst and the Part B contains the cross-linker. Unmixed – these syrupy materials will not cure. However, when mixed in a 1 to 1 ratio and heated to 350°F – liquid silicone compounds will cure in less than one minute. There are no by-products as found in the conventional peroxide cure silicones – therefore there is generally no need for a post-cure of molded LSR components.

Generally, platinum cure silicones will have better tensile strength and elongation properties than peroxide cure silicones. However, peroxide cure silicones usually have better compression set properties for gaskets requiring critical long term sealing at extended temperatures. Therefore – both of these silicone product families have their benefits.

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.