BISCO® MF1® Soft
BISCO® MF1® Soft is a soft-grade silicone foam cast into a block form with a density of 5.0 lb/ft³ and a compression force deflection range of 0.2–1.2 psi per ASTM D1056, designed for cushioning, sealing, and shock and vibration management applications including passenger rail car seating. The material is rated for recommended constant use to 392°F and passes FMVSS302 for flame resistance. It is FDA compliant in accordance with 21 CFR 177.2600.
Key Properties
- Compression Force Deflection: 0.2–1.2 psi (ASTM D1056)
- Tensile Strength: 12.5 psi (ASTM D412)
- Elongation: 45% (ASTM D412)
- Compression Set, 22 Hours @ 212°F @ 50%: 1.5% (ASTM D1056)
- Density: 5.0 lb/ft³ (ASTM D1056)
- Recommended Constant Use: 392°F
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- Specifications
- Applications
- General Info
- FAQs
Physical Properties
| Property | Value | Test Method |
| Thickness | Custom | — |
| Color | White | — |
| Material/Substrate | Silicone Foam | — |
| Density | 5.0 lb/ft³ | ASTM D1056 |
Mechanical Properties
| Property | Value | Test Method |
| Compression Force Deflection | 0.2–1.2 psi | ASTM D1056 |
| Compression Set, 22 Hours @ 212°F @ 50% | 1.5% | ASTM D1056 |
| Tensile Strength | 12.5 psi | ASTM D412 |
| Elongation | 45% | ASTM D412 |
| Tear Strength | >2.0 ppi | ASTM D624 |
| Low Temperature Flex | Pass | ASTM D1056 |
Thermal Properties
| Property | Value | Test Method |
| Recommended Constant Use | 392°F | — |
| Thermal Conductivity (Uncompressed) | 0.036 W/mK | ASTM C518 |
Electrical Properties
| Property | Value | Test Method |
| Dielectric Breakdown, Method C: Slow Rate of Rise (500 v/s) | 43 | ASTM D149 |
| Volume Resistivity | 7.0 × 10¹³ | ASTM D257 |
Flame & Fire Performance
| Property | Value | Test Method |
| FMVSS302 | Pass | — |
Environmental Performance
| Property | Value | Test Method |
| Ozone | Pass | — |
| UV Resistant | Pass | — |
Compliance
- FDA 21 CFR 177.2600 — Compliant
- FMVSS302 — Compliant (Pass)
- Seat cushions for passenger rail cars requiring FST-compliant soft silicone foam with maximum compression compliance
- General cushioning applications where low deflection force and vibration damping are the primary design requirements
- Sealing components in assemblies requiring a highly conformable foam under compression and environmental stress
- Shock and vibration management pads for absorbing mechanical forces and reducing transmitted vibration in equipment assemblies
- Lightweight impact protection components in transit and industrial applications
Common industries: Mass transit, industrial manufacturing, medical devices, electronics, transportation.
BISCO® MF1® Soft is the lowest-density grade in the MF1® bun silicone foam series at 5.0 lb/ft³, cast into block form and available in custom thicknesses. It is designed for applications requiring maximum compliance under compression, including passenger rail seating, general cushioning, sealing under compression and environmental stress, and shock and vibration management for absorbing mechanical forces and reducing vibration. The bun-cast construction allows conversion into custom thickness profiles for a wide range of finished part geometries.
The material achieves a compression set of only 1.5% at 22 hours, 212°F, 50% deflection — consistent with the other MF1® grades — despite being the softest and least dense grade in the series. Elongation is 45% per ASTM D412, and tear strength exceeds 2.0 ppi per ASTM D624. Low temperature flex passes per ASTM D1056. Thermal conductivity (uncompressed) is 0.036 W/mK per ASTM C518 — the lowest in the MF1® series, reflecting the lower density.
Ozone and UV resistance both pass. Dielectric breakdown (Method C, slow rate of rise, 500 v/s) is 43 per ASTM D149, and volume resistivity is 7.0 × 10¹³ per ASTM D257. FMVSS302 is passed for automotive and transit flame compliance.
What differentiates MF1® Soft from the Medium and Firm grades in the MF1® series?
MF1® Soft is the lowest-density and most compliant grade in the MF1® bun silicone foam series at 5.0 lb/ft³, with the lowest compression force deflection range of 0.2–1.2 psi. It requires less force to compress than the Medium (0.4–1.5 psi) and Firm (0.6–1.8 psi) grades, making it the appropriate selection where maximum conformance to surface geometry, low contact pressure, or high vibration absorption is the primary design requirement. Its dielectric breakdown value of 43 is also specific to this grade and differs from the 45 reported for the Firm and Medium grades.
Why is compression set critical for a soft bun silicone foam used in cushioning and sealing?
Compression set is especially important for soft foam grades because they operate at lower applied loads and are more susceptible to progressive deformation over time. A soft foam with high compression set will gradually "bottom out" in a seating application — losing the compliance that defines its value — or lose its sealing contact force in a joint. MF1® Soft's compression set of 1.5% at 22 hours, 212°F, 50% deflection demonstrates that the material maintains its low-force compression response over its service life, even under elevated thermal conditions.
What is the recommended constant use temperature for MF1® Soft?
The recommended constant use temperature is 392°F as listed on the TDS.
Is MF1® Soft suitable for regulated environments?
Yes. MF1® Soft is FDA compliant in accordance with 21 CFR 177.2600, supporting food-contact-adjacent and medical applications. It also passes FMVSS302 for automotive and transit flame compliance, and FST resistance performance is described as superior on the TDS, supporting mass transit interior applications.
How should MF1® Soft be specified?
Specify grade (MF1SOFTSIL), density (5.0 lb/ft³), CFD range (0.2–1.2 psi), color (White), applicable compliance requirements (FDA 21 CFR 177.2600, FMVSS302), custom thickness, dimensional tolerances, and finished format (bun block, sheet, or die-cut component).
