BISCO® HT-820 Firm
BISCO® HT-820 is a firm closed cell silicone foam engineered for applications requiring enhanced durability, high closure force, and sealing performance comparable to traditional sponge rubber. Rated from −67°F to 392°F, HT-820 delivers 15.3 psi compression force deflection at 25% and 2.6% compression set (22 hrs @ 212°F, 50%), offering higher tear and tensile strength than lighter-grade BISCO foams.
Key Properties
- Compression Force Deflection @ 25%: 15.3 psi (106 kPa) typical; spec 12–20 psi (82–138 kPa)
- Compression Set: 2.6% typical; spec <5% (22 hrs @ 212°F, 50%)
- Density: 24 lb/ft³ (384 kg/m³) typical
- Water Absorption: 0.5%; spec <5%
- Thermal Conductivity: 0.09 W/m°K
- Recommended Service Temperature: −67°F to 392°F
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- Specifications
- Applications
- General Info
- FAQs
Physical Properties
| Property | Value | Test Method |
| Material | Closed Cell Silicone Foam | — |
| Density | 24 lb/ft³ (384 kg/m³) typical | — |
| Thermal Conductivity | 0.09 W/m°K | ASTM C518 |
| Water Absorption | 0.5%; spec <5% | Internal (24 hrs, 2″ below surface) |
| Thicknesses Available | 0.031″, 0.063″, 0.094″, 0.188″, 0.250″ | — |
| Colors | Gray | — |
Mechanical Properties
| Property | Value | Test Method |
| Compression Force Deflection @ 25% | 15.3 psi (106 kPa) typical; spec 12–20 psi (82–138 kPa) | ASTM D1056 |
| Compression Set (22 hrs @ 212°F, 50%) | 2.6% typical; spec <5% | ASTM D1056 |
Flame & Fire Performance
| Property | Value | Test Method |
| Flame Resistance | V-0 | UL 94 (File E83967) |
| Flame Spread Index (Is) | <35, Flaming Mode | ASTM E162 |
| Smoke Density (Ds) @ 1.5 Minutes | <100, Flaming Mode | ASTM E662 |
| Smoke Density (Ds) @ 4 Minutes | <200, Flaming Mode | ASTM E662 |
| Burn Length | <100 mm/min | FMVSS 302 |
Thermal & Environmental Performance
| Property | Value | Test Method |
| Recommended Use Temperature | −67°F to 392°F (−55°C to +200°C) | Internal |
| Low Temperature Flexibility | Pass at −67°F (−55°C) / 3 min | ASTM D746 |
| Low Temperature Brittleness | Pass at −67°F (−55°C) / 5 hrs | ASTM D1056 |
| UV Resistance | Yes | — |
| Ozone Resistance | Yes | — |
Electrical Properties
| Property | Value | Test Method |
| Dielectric Strength | 66 V/mil | ASTM D149 |
| Dielectric Constant @ 1 kHz | 1.7 | ASTM D150 |
| Dissipation Factor @ 1 kHz | 0.006 | ASTM D150 |
| Dry Arc Resistance | 174 sec | ASTM D495 |
| Volume Resistivity | 10¹⁴ Ω·cm | ASTM D257 |
Outgassing (ASTM E595)
| Property | Value | Test Method |
| Total Mass Loss (TML) | 2.11% | ASTM E595 |
| Collected Volatile Condensable Materials (CVCM) | 0.63% | ASTM E595 |
| Water Vapor Regain (WVR) | 0.02% | ASTM E595 |
Compliance
- UL 94 V-0 — Compliant (File E83967)
- FMVSS-302 — Compliant
- AMS3196 — Compliant
- High closure force outdoor enclosure and communication cabinet gasketing
- Fine dust and wind-driven rain sealing in lighting and electronics enclosures
- Durable environmental sealing requiring higher mechanical strength than medium-grade foams
- Shock absorption and vibration isolation in demanding industrial environments
- Fire-resistant gasketing in transportation and electronic equipment
Common industries: telecommunications, electronics, lighting, transportation, and industrial equipment.
HT-820 is the firm grade in the HT-800 series, designed for enclosures and applications requiring a more durable, high-closure-force gasket. Its compact cell structure provides enhanced sealing against fine dust particles, wind-driven rain, and fire. HT-820 offers higher tear and tensile strength than the lighter BF and HT-870/HT-800 grades, making it the appropriate choice when mechanical durability under repeated compression and environmental exposure is required.
Excellent memory and low stress relaxation ensure sustained sealing force retention over the product life cycle, reducing maintenance costs associated with gasket softening and compression set failure. Rated to the most stringent UL flame standards and compliant with FMVSS-302 and AMS3196.
What differentiates HT-820 from other HT-800 series grades
HT-820 is the firm grade at 15.3 psi CFD typical, offering higher closure force, greater tear and tensile strength, and enhanced durability compared to HT-870 and HT-800. It is specified when a more mechanically robust, high-closure-force gasket is required.
Why is compression set critical?
Compression set measures long-term recovery after sustained compression. Lower values indicate better sealing force retention over the life of the application, reducing maintenance costs from gasket failure.
What is the operating temperature range?
−67°F to 392°F (−55°C to +200°C)
Is HT-820 suitable for regulated environments?
Yes. HT-820 complies with UL 94 V-0, FMVSS-302, and AMS3196 aerospace material specifications.
How should this material be specified
Specify grade (HT-820), thickness, compliance requirements, dimensional tolerances, and finished format. Note: available in Gray only.
