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BISCO® HT-840 : Extra-Firm Silicone Foam

BISCO® HT-840 : Extra-Firm Silicone Foam (closed cell)

BISCO® HT-840 silicone foam produced by Rogers Corporation is an extra firm grade silicone foam that offers improved durability and sealing. It is used to seal and protect various outdoor communication, lighting, and electronic enclosures from dust, wind driven rain, and fire. The resistance to elevated temperature, UV, flame (rated UL 94V-0) and compression set makes it the right choice for many gasket, sealing, cushioning, and gap filling applications.

Insul-Fab carries HT-840 in stock and fabricates the full line of Rogers Corporation BISCO® Silicone Products for your end use applications.  (link underlined text to the Insul-Fab Bisco Silicone page)


  • Consistent performance in extreme service temperatures
  • Extremely resilient to mechanical fatigue and compression set
  • Flame retardant, with UL 94 listed ratings V-0 and HF-1
  • Resistance to UV light, ozone, and chemicals
  • Extremely low smoke toxicity and flame spread
  • RoHS and REACH compliant
  • Low outgassing
  • Fabricates by die cutting and water jet
  • May be laminated with adhesive for attachment
  • Excellent technical assistance and sample support


BISCO® HT-840 Extra Firm is a durable silicone foam that offers a higher tear and tensile strength than lighter grade BISCO foams.  It is suitable for water seals in compressed applications.  The enhanced sealing and flame-retardant characteristics make this foam ideal for outdoor transportation, industrial, and electronics gasket applications where environmental seals are desired for the life of the product. 

BISCO silicones’ unique properties allow for consistent compression force, very limited compression set, and long-term performance reliability even at extreme low and high temperatures.  Also, they have been tested for flame and smoke toxicity ratings that meet the highest UL, railway, and aerospace standards.

BISCO® HT-840 Extra Firm Foam Properties



Typical Value




Thickness Range, in (mm)




Density, lb/ft3 (kg/m3)

ASTM D1056

27 (432)

Compression Force Deflection, psi @ (25%)

ASTM D1056


Compression Set,

max %

ASTM D1056

Test D @ 70oC

(158oF), 22hrs


Flammability, min. thickness, in (mm)

UL 94 V-0

Listed, (File E83967)

.063 (1.6)

Service Temperature, Continuous Rec.

High: 392oF (200oC)

Low: -67oF (-55oC)

Material Width, in


Format Availability

Fabricated Parts, Foam Tapes, Rolls, Sheets



RoHS Compliant


Halogen Free



Varies – See Availability Chart

Insul-Fab is proud to be designated a Major Converter of Rogers BISCO® and we commonly have many of their products in stock for distribution and fabrication.  Samples and part prototypes are readily available along with engineering support to choose the right material for your application.

Standard Product Availability

Within the most common BISCO product lines there are many thickness and color combinations available as standard, and more that are non-standard but available with minimum orders.  Please note, this information is subject to change.

BISCO® HT-840 Extra Firm Availability


Thickness, in (mm)



0.063 (1.60)


0.094 (2.39)


0.125 (3.18)


0.188 (4.76)


0.250 (6.35)


Contact us to find out if the BISCO SKU you are looking for is available in stock.  Samples and non-tooled application prototypes available on request.

In applications where the desired thickness is not standard, Insul-Fab can laminate two layers of material together with adhesive, or we can utilize another substrate, such as Formex or Lexan plastic film, to fill the desired gap and provide part rigidity while maintaining a stack-up of UL rated products for flammability requirements. 

Adhesive Backing and Lamination

Many applications for Rogers BISCO silicones require a pressure sensitive adhesive (PSA) with release liner on one or both sides for attachment in the end use.  Some BISCO products are available from the factory with pre-applied adhesive (special part number for designation). 

For more diverse adhesive selection and smaller lot sizes, Insul-Fab laminates silicone materials with PSA using a sophisticated in-house priming and lamination process to ensure a superior bond.  While many products bond well to primed BISCO, we recommend the following laminating adhesives.



3M 467MP and 3M 468MP

.002” and .005” unsupported acrylic (HP)

3M 9832 and 3M 9832HL

.005” double-coated acrylic (HP)

Concote CC593

.004” double-coated acrylic (GP)

 Unsupported acrylic adhesives offer an excellent bond and ability to conform to surface variations.  Double-coated or supported acrylics provide dimensional stability to larger parts or thin cross sections, to prevent stretching during end use application.

Other applications require the addition of a laminated film for surface protection, cosmetics, dimensional stability, or surface sliding.  We have available films such as PET, Formex, and Lexan for these occasions.


  • Environmental seals between sheet metal and plastic
  • Foam tapes for long lengths and door seals
  • Vibration isolation and energy absorption
  • Gaskets for extreme temperatures
  • Fire barriers and flame stops
  • Spacers for tolerance compensation and standoffs
  • Compression and rebound pads
  • Thermal insulation


Data Sheets

Brochures & Literature


Related Links   

Similar or related products 

The Rogers logo and BISCO® logos are trademarks of Rogers Corporation or one of its subsidiaries.  © 2019 Rogers Corporation. The technical data provided on this page is intended to assist you in material selection.  It is not intended to and does not create any warranties, express or implied.  The user should determine the suitability of the material for each application.


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