40 Durometer Natural Rubber Sheet
40 Durometer Natural Rubber Sheet is a soft-durometer polyisoprene elastomer sheeting compound offering a service temperature range of -70 to +180°F and elongation of 500% to 900%. Natural rubber delivers superior resilience, tensile strength, and excellent adhesion to fabrics and metals — performance characteristics that make it the material of choice for dynamic applications requiring energy absorption, abrasion resistance, and flex-crack resistance. At 40 Shore A, this grade provides maximum conformability within the Natural Rubber Sheet line and is well suited for low-load sealing, cushioning, and vibration isolation applications.
Key Properties
- Hardness, Shore A: 40 ± 5 (ASTM D2240)
- Elongation: 500–900%
- Service Temperature Range: -70 to +180°F
- ASTM D2000 / SAE J200 Classification: AA
- ASTM D-1418 Designation: NR
- Recommended Shelf Life: 3 years
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- Specifications
- Applications
- General Info
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Physical Properties
| Property | Value | Test Method |
| Hardness, Shore A | 40 ± 5 | ASTM D2240 |
| Elongation, % | 500–900 | — |
| Temperature Range | -70 to +180°F | — |
| ASTM D2000 / SAE J200 Classification | AA | — |
| ASTM D-1418 Designation | NR | — |
| MIL-R-3065 / SAE J-14 / MIL-STD-417 Classification | RN | — |
| Recommended Shelf Life | 3 years | — |
Mechanical Properties
| Property | Rating |
| Compression Set | Excellent |
| Abrasion Resistance | Excellent |
| Impact Resistance | Excellent |
| Resilience (Cold) | Excellent |
| Resilience (Hot) | Excellent |
| Flex Cracking Resistance | Excellent |
| Tear Resistance | Very Good |
| Flame Resistance | Poor |
Environmental Properties
| Property | Rating |
| Ozone Resistance | Poor |
| Weather Resistance | Poor to Fair |
| Sunlight Resistance | Poor |
| Steam Resistance | Fair to Good |
| Water Resistance | Very Good |
| Oxidation Resistance | Good |
| Gas Permeability | Fair to Good |
| Radiation Resistance | Fair to Good |
Compliance
- ASTM D2000 / SAE J200 Classification AA — Compliant
- MIL-R-3065 / SAE J-14 / MIL-STD-417 Classification RN — Compliant
- Automotive gaskets and seals
- Industrial belts and vibration dampers
- Construction components and expansion joints
- Conveyor systems and machine mounts
- Abrasion-resistant liners and wear pads
Common industries: Automotive, General Industrial, Construction, Material Handling, OEM Equipment.
40 Durometer Natural Rubber Sheet is the softest grade in the Natural Rubber Sheet line, combining the inherent mechanical advantages of polyisoprene — exceptional resilience, abrasion resistance, and flex-crack resistance — with a 40 Shore A hardness that provides maximum conformability for low-load sealing and cushioning applications. The high elongation range of 500% to 900% supports energy absorption and dynamic deflection across a wide range of contact conditions.
The -70 to +180°F service temperature range is among the broadest available in commercial elastomer sheeting, supporting both extreme cold-environment applications and moderate elevated-temperature service. Natural rubber’s outstanding adhesion to fabrics and metals makes this grade particularly suited to bonded and laminated constructions.
Compression set, abrasion resistance, impact resistance, and resilience are all rated Excellent; tear resistance is rated Very Good. Note that natural rubber has poor resistance to ozone, UV, sunlight, petroleum-based oils, and flame — application environments should be evaluated accordingly.
What differentiates 40 Durometer Natural Rubber Sheet from the 50 Durometer, 60 Durometer, and 70 Durometer grades?
40 Durometer Natural Rubber Sheet is the softest grade in the line at 40 Shore A, providing the greatest conformability and flexibility for low-load or dynamic applications. 50 Durometer Natural Rubber Sheet offers a medium-soft profile for applications requiring slightly higher compression resistance. 60 Durometer Natural Rubber Sheet is the mid-range grade, and 70 Durometer Natural Rubber Sheet is the firmest grade for high-load sealing and vibration isolation applications requiring maximum dimensional stability.
What makes natural rubber superior to synthetic elastomers for dynamic applications?
Natural rubber (polyisoprene) provides a combination of resilience, tensile strength, and elongation that synthetic elastomers typically cannot match at equivalent hardness. Its cold and hot resilience are both rated Excellent, meaning it recovers rapidly from dynamic deflection without significant heat buildup — a critical property for belts, mounts, and vibration isolators subjected to repeated loading cycles.
What is the service temperature range for 40 Durometer Natural Rubber Sheet?
The service temperature range is -70 to +180°F, as listed on the Technical Datasheet.
What are the limitations of natural rubber in outdoor or chemical environments?
Natural rubber has poor resistance to ozone, sunlight, UV exposure, and weathering, and is not recommended for contact with petroleum-based oils, fuels, gasoline, mineral oil, or most hydrocarbon solvents. Applications involving these exposures should consider a synthetic elastomer such as EPDM or nitrile. Salt water and sodium hydroxide are rated as having little or minor effect and are acceptable.
How should 40 Durometer Natural Rubber Sheet be specified?
Specify grade (40 Durometer Natural Rubber Sheet), thickness, applicable classification (ASTM D2000 AA or MIL-R-3065 RN as required), dimensional tolerances, and finished format.
