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What Is Tensile Strength? A Guide to Rubber Materials

Tensile strength is an important mechanical property used to evaluate the strength of rubber, plastic, metal, and other materials. For rubber products such as EPDM and silicone rubber sealing strips, tensile strength helps manufacturers and buyers understand how a material responds to pulling forces before it breaks.

But what exactly is tensile strength, how is it measured, and why should you consider it when choosing a rubber sealing product? This guide explains the basics and shows how tensile strength relates to real-world rubber applications.

1. What Is Tensile Strength?

Tensile strength is the maximum tensile stress a material withstands while being stretched before failure during a tensile test.

In simple terms, it indicates how much pulling stress a material can withstand before it breaks.

Tensile strength is generally expressed in megapascals (MPa), newtons per square millimeter (N/mm²), or pounds per square inch (psi). One MPa is equivalent to one N/mm².

For rubber materials, tensile strength is an important indicator of mechanical performance. However, it should not be used alone to determine whether a rubber product is suitable for a particular application.

2. How Is Tensile Strength Calculated?

Tensile strength is calculated by dividing the maximum tensile force recorded during a test by the specimen's original cross-sectional area.

Formula:

Tensile Strength = Maximum Tensile Force ÷ Original Cross-Sectional Area

For example, if a rubber specimen has an original cross-sectional area of 25 mm² and reaches a maximum tensile force of 500 N, its tensile strength is:

500 N ÷ 25 mm² = 20 N/mm² = 20 MPa

This example illustrates the calculation only. Actual tensile strength values vary depending on the rubber compound, specimen preparation, and testing conditions.

3. How Is Tensile Strength Tested?

Tensile strength is commonly measured using a tensile testing machine. A rubber specimen is securely held between two grips and pulled at a controlled rate until it breaks.

During the test, the machine records the applied force and the specimen's extension. The resulting data can be used to determine tensile strength, elongation at break, and other tensile properties.

Two commonly referenced standards for rubber tensile testing are:

• ASTM D412: Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension.

• ISO 37:2024: Rubber, Vulcanized or Thermoplastic—Determination of Tensile Stress-Strain Properties.

The results can be affected by factors such as test temperature, extension rate, specimen dimensions, and preparation methods. For meaningful comparisons, samples should be tested under comparable conditions.

4. What Is the Difference Between Tensile Strength and Elongation at Break?

Tensile strength and elongation at break are related but measure different properties.

A rubber compound may have high tensile strength without having the highest elongation at break. Likewise, hardness does not directly tell you how much tensile stress a rubber material can withstand.

These properties should be considered together when selecting a material for a particular sealing application.

5. Tensile Strength of EPDM vs. Silicone Rubber

EPDM and silicone rubber are widely used materials for sealing products, but they have different characteristics. Their tensile strength depends on the specific formulation, hardness, manufacturing process, and test conditions.

EPDM Rubber

EPDM rubber is commonly selected for applications requiring resistance to outdoor weathering, ozone, and moisture.

EPDM sealing strips may be used in construction, automotive systems, solar panel assemblies, and other outdoor applications. When evaluating an EPDM compound, buyers should consider tensile strength alongside elongation at break, hardness, compression set, and environmental resistance.

Silicone Rubber

Silicone rubber is often chosen for applications requiring flexibility across a broad temperature range. Specific silicone compounds can also be formulated for different industrial and sealing requirements.

When evaluating silicone rubber sealing strips, tensile strength should be considered together with elongation, tear resistance, hardness, operating temperature, and other application-specific properties.

Which material has higher tensile strength?

There is no universal answer. The result depends on the grades and formulations being compared. Buyers should request technical data for the specific EPDM and silicone compounds under consideration rather than assuming one material always has higher tensile strength.

Conclusion

Tensile strength is an important parameter for understanding the mechanical performance of rubber materials. It helps manufacturers and buyers evaluate resistance to pulling forces, compare compounds, and support quality control.

For EPDM and silicone rubber sealing strips, however, tensile strength is only one part of the overall material specification. The right choice also depends on flexibility, sealing requirements, environmental exposure, product geometry, and other performance criteria.

When sourcing custom rubber sealing strips, provide your application details, drawings, dimensions, operating conditions, and required material properties. This information helps a manufacturer identify a suitable compound and profile for your needs.

Looking for custom EPDM or silicone rubber sealing strips? Contact our team to discuss your application, technical specifications, and customized manufacturing requirements.