BISCO® RS-870 Soft
BISCO® RS-870 is a soft cellular silicone sponge with a density of 16 lb/ft³ and a compression force deflection of 5 psi per ASTM D1056, designed to retain the lightness of a foam while providing the enhanced sealing capability of a traditional sponge rubber. The material has a temperature range of -67°F to 392°F, passes UL 94 V-0 and UL 94 HF-1 at a third-party laboratory, and is UV and ozone resistant. RS-870 is an alternative to HT-870.
Key Properties
- Compression Force Deflection: 5 psi (ASTM D1056)
- Compression Set, 22 Hours @ 212°F @ 50%: 3.5% (ASTM D1056)
- Water Absorption: 1.0% (ASTM D1056)
- Density: 16 lb/ft³
- Temperature Range: -67°F to 392°F
- UL 94 V-0 / UL 94 HF-1: Pass (Meets at third party lab)
We want to help!
Enter your information and we'll get you in touch with our knowledgable staff. We know how important to the right product for your project.
Request a Consultation
- Specifications
- Applications
- General Info
- FAQs
Physical Properties
| Property | Value | Test Method |
| Thickness | 1/8″, 3/16″, 1/4″ | — |
| Color | Gray | — |
| Material/Substrate | Silicone Sponge | — |
| Density | 16 lb/ft³ | — |
Mechanical Properties
| Property | Value | Test Method |
| Compression Force Deflection | 5 psi | ASTM D1056 |
| Compression Set, 22 Hours @ 212°F @ 50% | 3.5% | ASTM D1056 |
| Water Absorption | 1.0% | ASTM D1056 |
| Low Temperature Brittleness | -67°F | ASTM D746 |
Thermal Properties
| Property | Value | Test Method |
| Temperature Range | -67°F to 392°F | — |
Flame & Fire Performance
| Property | Value | Test Method |
| UL 94 V-0 | Pass | Meets at third party lab |
| UL 94 HF-1 | Pass | Meets at third party lab |
Environmental Performance
| Property | Value | Test Method |
| UV Resistance | Yes | — |
| Ozone Resistance | Yes | — |
Compliance
- UL 94 V-0 — Compliant (Meets at third party lab)
- UL 94 HF-1 — Compliant (Meets at third party lab)
- Environmental seals against dust, moisture, air, and light penetration in outdoor enclosures including lighting fixtures, HVAC units, and electronic cabinets where low closure force is available
- Shock absorbing cushions and gaskets in automobiles requiring a soft, lightweight silicone sponge
- Shock absorbing gasket and cushioning components in household appliances subject to vibration and thermal cycling
- Environmental sealing in low-load enclosure assemblies requiring UL 94 V-0 and HF-1 rated soft silicone sponge
- Replacement or alternative sealing for HT-870 applications
Common industries: Electronics, HVAC, automotive, appliances, outdoor enclosures.
BISCO® RS-870 is the softest and lowest-density grade in the BISCO® RS cellular silicone sponge series at 16 lb/ft³ and 5 psi CFD, positioned as a direct alternative to HT-870. It is designed for environmental sealing applications where low closure force is available — such as lighting enclosures, HVAC units, and electronic cabinet doors — as well as shock absorbing cushions and gaskets in automobiles and appliances.
Available in 1/8″, 3/16″, and 1/4″ thicknesses, it provides maximum compliance under minimal applied load while retaining the environmental and thermal resistance of the silicone sponge family.
RS-870 achieves the lowest compression set in the RS series at 3.5% at 22 hours, 212°F, 50% deflection per ASTM D1056 — lower than the 4.0% recorded for RS-800, RS-820, and RS-840 — indicating superior recovery after sustained compression for this soft grade. Low temperature brittleness is rated at -67°F per ASTM D746, consistent with the full temperature range of -67°F to 392°F. Water absorption is 1.0% per ASTM D1056.
UV resistance and ozone resistance are both confirmed Yes. The material exhibits temperature independency across its service range as stated on the TDS.
Compliant with UL 94 V-0 and UL 94 HF-1 (meets at third party lab).
What differentiates RS-870 from the other grades in the BISCO® RS series?
RS-870 is the softest and lowest-density grade in the BISCO® RS series at 16 lb/ft³ and 5 psi CFD — substantially more compliant than RS-800 (25 lb/ft³, 11.5 psi CFD), and far softer than RS-820 and RS-840 (both 30 lb/ft³, 22.5 psi CFD). It also achieves the lowest compression set in the series at 3.5%, compared to 4.0% for all other RS grades. RS-870 is the appropriate selection when low closure forces must be sufficient to compress the gasket fully, and it is the only RS grade described for shock absorbing applications in automobiles and appliances.
Why is compression set critical for a soft cellular silicone sponge used in environmental sealing and shock absorption?
Soft sponge grades are especially susceptible to compression set because they are compressed under lower applied loads and may remain under sustained compression for extended periods. In environmental sealing, a soft sponge with high compression set progressively loses contact force against the enclosure flange, allowing gaps to open and permitting ingress of dust, moisture, or air. In shock absorption, permanent set reduces the material's ability to return to its original geometry between impact events, degrading cushioning effectiveness over time. RS-870's compression set of 3.5% at 22 hours, 212°F, 50% deflection — the lowest in the RS series — confirms excellent dimensional recovery even at elevated temperature for this soft grade.
What is the temperature range for RS-870?
The temperature range is -67°F to 392°F as listed on the TDS. Low temperature brittleness is rated at -67°F per ASTM D746.
Is RS-870 suitable for flame-rated environments?
Yes. RS-870 passes UL 94 V-0 and UL 94 HF-1 at a third-party laboratory as listed on the TDS.
How should RS-870 be specified?
Specify grade (RS-870), thickness (1/8", 3/16", or 1/4"), color (Gray), applicable compliance requirements (UL 94 V-0, UL 94 HF-1), dimensional tolerances, and finished format (sheet, slit roll, or die-cut gasket).
