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The Elastomerics Blog by Stockwell Elastomerics

Wednesday, October 22, 2014

Insulation for Silicone Rubber Heaters and Flexible Heaters

silicone foam insulation
Silicone Rubber Heater Insulation Materials

Stockwell Elastomerics supplies silicone sheet materials and custom silicone parts to commercial and industrial markets.  While Stockwell Elastomerics does not supply uncured or semi-cured silicone sheets for the construction of flexible heater, silicone foam and silicone sponge sheets are sold as insulation backers to the flexible heater / silicone rubber heater markets.  These high temperature foam backings help improve heater efficiency by reducing heat loss. Heater foam insulation from Stockwell Elastomerics may be permanently bonded with silicone RTV or tacked in place with DP-1001 peel and stick backing.

Silicone Foam Sheet Insulation - has an operating temperature of 200°C (392°F) with intermittent exposures to 250°C (482°F).

     Open cell silicone foam (BF-1000) - very good insulation and has a UL 94V-0 flame rating.
     Thermal conductivity = 0.06 W/m-K.

     Closed cell silicone foam (HT-800) - good insulation, UL 94V-0 flame rating and water resistance.
     Thermal conductivity = 0.09 W/m-K.

Silicone Sponge Sheet Insulation – has an operating temperature of 260°C (500°F)
     High temperature closed cell silicone sponge offers higher temperature resistance, good
     insulation and is tougher than the foams.  Closed cell sponges are available with
     UL 94HB and UL 94V-0 flame ratings.
     Typical thermal conductivity = 0.11 W/m-K.

Silicone sheet insulation is available in a wide range of thickness and sizes.  Stockwell Elastomerics offers heater insulation materials in sheets or rolls 36” wide; custom cut insulation pads are also available. Additionally, Stockwell Elastomerics offers silicone sheet materials with or without adhesive backing. High temperature silicone adhesive or moderate temperature acrylic adhesive backings are available too.

For more information about silicone insulation sheets for silicone rubber heaters and flexible circuits, please contact Stockwell Elastomerics at service@stockwell.com or 1-800-523-0123.

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posted by Steve Hughes at 11:27 AM

Friday, October 03, 2014

Custom Foam Port Plugs for Environmental Test Chambers

Stockwell Elastomerics is custom gasket manufacturer with a core competence in silicone materials. Typically the gaskets and rubber components made by Stockwell Elastomerics are used to protect electronics from the environment. Conversely, Stockwell Elastomerics Port Plugs are used to keep the environment inside the enclosure.
Custom Port Plugs
Custom Silicone Foam Port Plugs

Environmental testing chamber plugs are used for testing high temperature, sub-freezing temperature and humidity. Port Plugs from Stockwell Elastomerics can be made to standard sizes for 2”, 3”, 4”, 6” round ports; as a rapid response supplier, Stockwell Elastomerics can quickly waterjet cut custom geometries with minimal additional cost.

Stockwell Elastomerics Port Plugs


The pictures illustrate the advantage of a concentric plug, having foam on either side of the cable allows the foam to conform more tightly. Large rectangular blocks and port plugs with custom cutouts are easily produced with minimal additional charge.






Lower cost single layer plugs - in a previous post it was mentioned that the black layered plugs cost less with a shorter lead time, recent events have shifted this. Now the single layer with the grey closed cell silicone foam top layer offers better cost savings.

Stockwell Elastomerics manufactures custom gaskets for a wide variety of industries needing to meet rugged environmental conditions, from high heat, freezing, high humidity. Many OEM customers who buy silicone gaskets also buy custom port plugs for their test chambers.

For more information about Stockwell Elastomerics Port Plugs, custom port plugs or custom silicone gaskets, please call 1-800-523-0123 or email service@stockwell.com.

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posted by Steve Hughes at 3:58 PM

Thursday, August 21, 2014

Why is Silicone Rubber Ugly Orange?

Orange Silicone Rubber
Orange rubber sheets or orange rubber gaskets are quite often silicone rubber, but color can be misleading.  The traditional, arguably ugly, orange comes from an iron oxide pigment; this same pigment can be uses in a variety of rubber or thermoplastic rubber materials.  To this point, impostor materials can be manufactured that look and feel like silicone but don’t have the same physical properties.  This is very important if the functional requirements matter; properties such as high temperature resistance, UV resistance, ozone resistance or longevity.  Higher quality silicone rubber sheets may be post cured which enhances the physical properties like compression set and out-gassing.   So when rubber performance is critical, it’s important to work with a manufacturer who understands and certifies the material they are selling.

Not surprisingly many OEMs do not want the burnt orange color when the aesthetics are a factor, meaning when the gasket is visible to the end user.  Responding to the market, many raw material suppliers offer gum based silicones in black, grey and other colors.  Generally, the ugly orange pigment is used for gum based,
Silicone Injection Molding Colors
peroxide cured silicone rubber materials.  Liquid based, platinum cured silicones are colorless two part liquids that are mixed and molded or cast. The liquid based platinum silicones are offered as colorless, transparent, black, grey or in variety of colors.

Stockwell Silicone Parts
Is the traditional orange silicone color ugly?  That’s a point for debate, but when it comes to performance vs. color, performance typically wins. For more information on silicone sheet materials, molded silicone parts or silicone gaskets and other rubber components, please contact Stockwell Elastomerics at service@stockwell.com or call 1-800-523-0123.

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posted by Steve Hughes at 4:41 PM

Tuesday, July 01, 2014

Silicone Foam Port Plugs for Environmental Test Chambers

environmental chamber plugs
layered foam plug
silicone foam port plug, layered
silicone foam plugs for environmental chambers
silicone foam port plugs

Stockwell Elastomerics manufactures replacement foam port plugs for environmental test chambers. Silicone foam plugs have excellent temperature and humidity resistance and offer very good thermal insulation. Custom sizes and profiles are available without any tooling charge; most plugs are slightly oversized to make a tight fit/seal in the port.

Stockwell Elastomerics’ silicone foam port plugs are made in several configurations.  The white, single piece plugs are available with or without a dense closed cell top layer (grey layer shown in picture).  A lower cost and short lead time option is the layered silicone foam plug (shown in black).  The layered foam port plugs are made from bulk produced silicone foam that has skin on each side and fine pitch cells.  The layered version does not require the additional grey top layer but is still available.

For more information or to order silicone foam port plugs for environmental test chambers, please contact Stockwell Elastomerics at 1-800-523-0123 or email service@stockwell.com.

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posted by Steve Hughes at 4:43 PM

Monday, June 02, 2014

EMI Gasket Material with Conductive Reinforcement

EMI management is a must for OEMs manufacturing electronic devices or equipment containing electronics.  EMI gaskets made from rubber material such as silicone and fluorosilicone lose some physical strength due to the conductive particle fill.  This is most apparent in tensile strength in thin EMI gasket materials. To address this, Stockwell Elastomerics now offers components manufactured from SNE-556-R conductive silicone EMI gasket material with a conductive reinforcement.

SNE-556-R is 65 durometer (Shore "A") with volume resistivity that challenges high cost silver coated aluminum filled products, but at a fraction of the cost. Additionally, it is manufactured in continuous sheet rolls allowing for manufacturing large EMI gaskets. The reinforcement enhances the conductivity of the rubber as well as giving dimensional stability to cut parts. An example is an EMI enclosure with many bolts, the reinforcement prevents the gasket from stretching during installation ensuring holes in the EMI gasket align well with the fastener hole in the enclosure.

Benefits of SNE-556-R reinforced EMI gasket material:
  • High Conductivity EMI gasket
  • Continuous EMI Sheet Roll
  • Cost benefit from nickel graphite filled silicone
  • Dimensional stability of cut EMI shielding gaskets
  • Environmental sealing EMI Gasket
  • Available with 3M conductive adhesive backing
Stockwell Elastomerics manufactures EMI gaskets and EMI shielding components for the technology and defense sectors.  Products include, molded EMI components for medical device, waterjet EMI gaskets for defense and aerospace, EMI connector gaskets and emi card cage gaskets for a multitude of industries.

For more information on SNE-556-R reinforced EMI gasket material and other silicone gaskets, please contact Stockwell Elastomerics at 1-800-523-0123 or email service@stockwell.com,

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posted by Steve Hughes at 1:59 PM

Wednesday, May 07, 2014

Digital Signage Gasket, Protecting Capital Investment

Electric signage is going through its digital revolution; as cost of hardware decreases and connectivity improves, digital signage is becoming the preferred means of advertising. Examples include: large outdoor LED billboards, electronic posters, interactive kiosks and touch screens. As with most electronics, digital displays need to be protected from their environment. Outdoor signage needs to function in a wide range of conditions such as wind driven rain, snow, and extreme temperatures.  Interactive advertising needs to be protected from rough use and spills. An additional consideration is the management of electromagnetic interference (EMI).

While relatively new to signage and advertising, these environmental and EMI consideration have been managed for many years in industries such as telecommunications, outdoor lighting, electric controls and military electronics. Stockwell Elastomerics has been providing sealing solutions and ruggedizing materials to OEMs for decades.  With a wide range of materials and manufacturing capabilities, Stockwell offers high performance gasket tapes as well as custom cut parts. Applications engineers are available to help specify the most cost effective material and process to meet performance and regulatory requirements.

In the works is UL 48B, which will address digital signage.  UL 48B will have the same basic requirements for gaskets as UL 48 (electric signage); however display manufacturers will likely need to surpass these due to the more sensitive electronics. Additionally, many indoor or public use displays may require materials that meet UL94 flame requirements.


Material Touch Brochure Available for UL 48 SAM


Stockwell Elastomerics offers Applications Engineering support to help with material selection. Having comprehensive inventory and in-house manufacturing allows Stockwell to manufacture pre-production through full production quickly.
For more information on gasket solutions for digital signage and interactive digital displays, please visit www.stockwell.com, email service@stockwell.com or call 1-800-523-0123.

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posted by Steve Hughes at 11:55 AM

Tuesday, April 15, 2014

Open Cell Foam vs. Closed Cell Foam

Stockwell Elastomerics inventories hundreds of gasket materials and cushion materials to meet a wide range of performance requirements. While applications such as mobile military electronics, outdoor lighting, NEMA enclosures all seem very different, they often share the need to withstand environmental conditions of heat, cold, UV, ozone and most importantly seal out water and dust.

To achieve a good water seal there are several factors, the most important is selecting the proper material.  Sealing sheet metal or plastic enclosures very often need soft, expanded rubber materials that can be readily compressed. Many of the rubber gasket materials like silicone, urethane, neoprene, EPDM are available in expanded form; an analogy is like adding yeast in bread, a blowing agent is mixed with these polymers to make them expand creating pockets of air.  Most water sealing applications requires these pockets to be closed off from each other, called closed cell foam or closed cell sponge.  When the pocket are open to one another, they are called open cell foam or open cell sponge.

Open Cell Example: A kitchen sponge has open cells; the open, connected cells allow water to pass from one cell to the other, allowing it to hold water used for cleaning.
Closed Cell Example: A scuba diver's wetsuit, where the adjacent cells are closed off from one another.  The trapped air in the neoprene make it soft and lightweight yet does not absorb water even under pressure of being submerged.
The video below shows two expanded silicone products, an open cell silicone foam and a closed cell silicone sponge.  Aside from the water picked up from the cut cells on the edges, the close cell gasket material does not absorb water.




For more information on closed cell rubber for water gaskets and open cell foams for dust and light spray gaskets.  Please visit www.stockwell.com, email service@stockwell.com or call 1-800-523-0123.

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posted by Steve Hughes at 10:42 AM