kSil® US40
kSil® US40 is a solid silicone elastomer with a 40 Shore A durometer, offering high elongation of 550% and a tensile strength of 9 MPa. It meets AA-59588 and AMS 3301 specifications and is compliant with FAR 25.853 Horizontal and FDA 21 CFR 177.2600. The material is available in red-orange, black, and grey.
Key Properties
- Durometer: 40 Shore A (ISO 48-4)
- Tensile Strength: 9 MPa (ISO 37 Type 2)
- Elongation: 550% (ISO 37 Type 2)
- Compression Set, 24 Hours @ 150°C: 24% (ISO 815, 24h @150°C)
- Tear Strength: 18 N/mm (ASTM D624 Die B)
- Thermal Conductivity: 0.24 W/m·°C (ASTM C518)
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- Specifications
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- General Info
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Physical Properties
| Property | Value | Test Method |
| Thermal Conductivity | 0.24 W/m·°C | ASTM C518 |
| Colors Available | Red-orange, Black, Grey | Visual |
Mechanical Properties
| Property | Value | Test Method |
| Durometer | 40 Shore A | ISO 48-4 |
| Tensile Strength | 9 MPa | ISO 37 Type 2 |
| Elongation | 550% | ISO 37 Type 2 |
| Tear Strength | 18 N/mm | ASTM D624 Die B |
| Compression Set — 24 Hours @ 150°C | 24% | ISO 815, 24h @150°C |
Compliance
- AA-59588 — Compliant
- AMS 3301 — Compliant
- FAR 25.853 Horizontal — Compliant
- FDA 21 CFR 177.2600 — Compliant
- Flexible gaskets and seals where a soft-medium durometer and high elongation are required
- Food contact components in processing and packaging equipment
- Aerospace sealing applications requiring AA-59588 and AMS 3301 qualification
- Aerospace flame compliance applications per FAR 25.853 Horizontal
- Automotive sealing components requiring a flexible, compliant silicone elastomer
Common industries: Aerospace, Automotive, Food Processing, Industrial Manufacturing.
kSil® US40 is a soft-medium grade in the kSil® US general purpose solid silicone series, with a 40 Shore A durometer. It is qualified to AMS 3301 and meets AA-59588 aerospace specifications, making it suited for flexible aerospace and automotive sealing applications as well as food contact components where high elongation and regulatory compliance are required.
The material achieves a tensile strength of 9 MPa and an elongation of 550%, both per ISO 37 Type 2, along with a tear strength of 18 N/mm per ASTM D624 Die B. Compression set is 24% after 24 hours at 150°C per ISO 815. Thermal conductivity is 0.24 W/m·°C per ASTM C518. US40 is available in red-orange, black, and grey.
Compliant with AA-59588, AMS 3301, FAR 25.853 Horizontal, and FDA 21 CFR 177.2600.
What differentiates US40 from US30 and US50 in the kSil® US solid silicone series?
US40 sits between the ultra-soft US30 (800% elongation, no listed durometer) and the medium US50 (50 Shore A, 310% elongation). At 40 Shore A and 550% elongation, it provides a soft-medium balance of flexibility and firmness, combined with AMS 3301 aerospace qualification not shared by all grades in the range.
Why is compression set critical for solid silicone elastomers like US40?
Compression set measures how well a material recovers its original thickness after being held under compressive load at elevated temperature. For sealing applications, a high compression set results in permanent deformation and loss of contact force over time. US40 exhibits a compression set of 24% after 24 hours at 150°C per ISO 815.
What is the operating temperature range for US40?
No discrete operating temperature range is specified on the manufacturer's TDS for US40. The compression set test condition is 150°C. Contact H-O Products for service temperature guidance specific to your application.
Is US40 suitable for aerospace or food contact environments?
Yes. US40 is qualified to AMS 3301, meets AA-59588, and is compliant with FAR 25.853 Horizontal for aerospace applications. It is also compliant with FDA 21 CFR 177.2600 for food contact use.
How should US40 be specified?
Specify grade (US40), thickness, color (Red-orange, Black, or Grey), compliance requirements, dimensional tolerances, and finished format.
