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When selecting silicone rubber for industrial seals, buyers often start with hardness.
A typical request might be:
“We need a low-temperature silicone rubber, preferably a harder grade.”
But higher hardness does not automatically mean better sealing performance.
A seal must provide suitable contact pressure while accommodating the equipment's geometry and operating conditions.
This becomes particularly important when the seal is exposed to low temperatures.
Shore A hardness describes a material's resistance to indentation under specified test conditions.
It is useful when comparing elastomer grades, but it does not directly measure sealing performance.
A harder compound may provide greater resistance to deformation in some situations.
A softer compound may conform more readily to certain sealing surfaces.
Neither is automatically superior.
The appropriate choice depends on the seal geometry, compression, pressure and service conditions.
At low temperatures, the stiffness and recovery behavior of an elastomer can change.
For an O-ring or gasket, maintaining suitable contact with the sealing surfaces is important.
A material may remain intact without cracking but still fail to meet the required sealing performance.
This is why low-temperature evaluation may need to consider:
Elastic recovery
Compression behavior
Changes in stiffness
Seal geometry
Contact pressure
Exposure duration
Thermal cycling
A single temperature value does not fully describe the behavior of a finished seal.
The IOTA 3830 Series Phenyl HTV Silicone Rubber is positioned for molded and extruded silicone rubber applications.
Published application directions include seals, gaskets, tubing and damping components for demanding temperature conditions.
The series includes several grades with different listed hardness values:
| Grade | Listed hardness |
|---|---|
| IOTA 3830 | 30 |
| IOTA 3835 | 35 |
| IOTA 3840 | 40 |
| IOTA 3850 | 52 |
| IOTA 3860 | 59 |
These options can support preliminary grade selection.
However, the published values should not be treated as guaranteed performance results for every finished sealing component.
Processing, curing and finished-part design must also be considered.
A relatively softer grade may be worth evaluating when the design requires easier deformation under a specified compression load.
A harder grade may be worth evaluating where the application requires greater support or resistance to deformation.
But this does not establish which grade will provide the lowest leakage.
For example, two seals made from the same rubber grade may perform differently if their cross-sections, groove dimensions or compression conditions differ.
The material and seal design should therefore be evaluated together.
Depending on the application, a meaningful evaluation may include:
Low-temperature behavior
Assess stiffness and recovery under the intended temperature conditions.
Compression set
Measure recovery after compression under defined test conditions.
Media compatibility
Check exposure to the actual oil, fuel or other operating medium.
Finished-part sealing
Verify leakage performance in the intended geometry.
Processing and curing
Confirm that the material can be processed using the available manufacturing equipment.
Before requesting a grade recommendation, provide:
Seal type and dimensions
Minimum and maximum operating temperatures
Target hardness
Contact medium
Compression and pressure conditions
Existing material
Required finished-part tests
Processing and curing method
These details are more useful than specifying hardness alone.
Does higher Shore A hardness always improve sealing?
No. Sealing depends on material behavior, geometry, compression and operating conditions.
Which hardness grades are available in the IOTA 3830 Series?
The published product information lists grades with hardness values of 30, 35, 40, 52 and 59.
Can phenyl silicone rubber be used for low-temperature seals?
Certain phenyl silicone rubber grades are candidates for low-temperature applications, subject to formulation and finished-part validation.
Is low-temperature brittleness testing enough?
No. Elastic recovery, compression behavior and actual sealing performance may also need evaluation.
Can one hardness grade replace another directly?
A direct replacement should not be assumed. The finished component should be tested under the required conditions.
IOTA 3830 Series Phenyl HTV Silicone Rubber
Application Boundary: Published material properties support preliminary screening. Final low-temperature sealing performance depends on compound formulation, curing, seal design and actual service conditions.
