High and Low Temperature Tensile Performance Testing of Sealing Strips: Standards, Methods, and Eval

High and low temperature tensile performance testing of sealing strips evaluates how rubber and elastomeric seals maintain tensile strength, elongation, and stress-strain behavior under extreme thermal conditions. This testing is essential for automotive, construction, and industrial applications where sealing integrity must be guaranteed across service temperatures ranging from -40°C to +150°C. By following internationally recognized standards such as ISO 37, ASTM D412, and GB/T 528, accredited third-party laboratories provide reliable data that supports material selection, product certification, and quality control.

Technical Overview

Sealing strips are flexible elastomeric components widely used in vehicles, buildings, appliances, and industrial equipment to block dust, water, air, noise, and vibration. They are typically manufactured from EPDM rubber, PVC, silicone rubber, thermoplastic elastomers (TPE/TPV), or foam materials, and their mechanical performance is highly sensitive to temperature. At elevated temperatures, polymer chains soften and degrade, reducing tensile strength and elongation; at sub-zero temperatures, materials stiffen and become brittle, increasing the risk of cracking during installation or dynamic service.

High and low temperature tensile performance testing subjects sealing strip materials to controlled thermal environments—either during the tensile test itself or after thermal aging—and measures key mechanical properties under those conditions. The results reveal whether a sealing strip can maintain structural integrity and elastic recovery throughout its expected service life. Testing is performed in accordance with recognized standards published by ISO, ASTM, and GB (Chinese national standards), and is commonly carried out by accredited third-party laboratories as part of incoming material inspection, supplier qualification, and product certification programs.

Testing Samples

Dense Rubber Sealing Strips

Dense (solid) sealing strips, most commonly extruded from EPDM compounds, form the load-bearing skeleton of automotive door seals, window channels, and trunk seals. Standard dumbbell-shaped specimens are die-cut from the dense rubber portion of the profile, or from companion test plaques of the same compound and cure state, and evaluated for tensile strength and elongation at break at both elevated and reduced temperatures.

Sponge and Foam Sealing Strips

Cellular or sponge sealing strips contain closed-cell or open-cell structures that provide compression and recovery behavior. Because foam morphology strongly affects tensile response, specimens are prepared from the sponge bulb region of the profile. Testing at temperature extremes verifies that the foam does not become brittle in cold climates or lose elasticity in hot environments.

PVC and Thermoplastic Elastomer Sealing Strips

Flexible PVC and TPE/TPV sealing strips are widely used in building doors, windows, and curtain walls. These thermoplastic materials exhibit pronounced softening near their glass transition and melting ranges, making high-temperature tensile testing and heat aging retention studies particularly important for confirming long-term performance in sun-exposed installations.

Silicone Rubber Sealing Strips

Silicone seals serve high-temperature applications such as oven doors, industrial furnaces, and electrical enclosures. Silicone rubber retains flexibility across an exceptionally wide temperature range, and tensile verification at temperatures up to 200°C or higher confirms suitability for extreme service conditions.

Testing Items

Depending on the product specification and end-use requirements, the following properties are typically measured as part of a high and low temperature tensile evaluation:

• Tensile strength at specified high and low temperatures (e.g., -40°C, -20°C, +70°C, +100°C, +150°C)
• Elongation at break under temperature-controlled conditions
• Tensile stress at a given elongation (100% or 300% modulus) at ambient and extreme temperatures
• Retention of tensile strength after hot air aging, expressed as a percentage of the original value
• Retention of elongation at break after hot air aging or low temperature exposure
• Change in hardness and stress-strain behavior following thermal conditioning
• Behavior after combined aging sequences such as heat aging followed by low temperature flexing

Testing Methods

Reference Standards

The core tensile test methods are ISO 37 (Rubber, vulcanized or thermoplastic—Determination of tensile stress-strain properties), ASTM D412 (Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension), and GB/T 528, the corresponding Chinese national standard. Thermal aging preconditioning is governed by ISO 188, ASTM D573, and GB/T 3512, while product-specific requirements for automotive sealing strips are defined in standards such as GB/T 21282 and related OEM specifications.

Specimen Preparation and Conditioning

Dumbbell specimens—commonly Type 1, Type 2, or Type 1A depending on the standard and available material—are die-cut with the thickness of the finished part measured at three points along the test section. Where the profile geometry prevents cutting full dumbbells, straight strip specimens of uniform cross-section may be permitted with an agreed correction factor. Prior to testing, specimens are conditioned in a standard laboratory atmosphere of 23 ± 2°C and 50 ± 5% relative humidity for a minimum of 16 hours.

Equipment and Temperature Control

Testing is conducted using a universal tensile testing machine equipped with an environmental chamber capable of covering the required temperature range, typically -40°C to +150°C with stability of ±2°C. Liquid nitrogen or mechanical refrigeration provides low temperature capability, while resistance heating supplies elevated temperatures. Specimens are soaked at the set point for a minimum equilibration period—commonly 10 to 30 minutes depending on thickness—before the test begins, ensuring the entire cross-section reaches thermal equilibrium.

Test Procedure

The specimen is mounted in the grips inside the chamber, brought to the target temperature, and extended at the crosshead speed specified by the standard, typically 500 mm/min for ISO 37 and GB/T 528. Force and extension are recorded continuously until rupture, and tensile strength, elongation at break, and stress at specified elongation are calculated from the recorded data. For aged conditions, replicate specimens are first exposed in a hot air aging oven for a defined period (for example 72 h, 96 h, or 168 h at the specified temperature), cooled, and then tested at either ambient or specified temperatures.

Retention Calculation and Evaluation

The retention of a property after thermal exposure is calculated as the aged value divided by the original unaged value, multiplied by 100%. Typical acceptance criteria for automotive EPDM sealing strips require tensile strength retention of at least 75% to 85% and elongation retention of at least 60% to 75% after aging, though exact limits are set by the applicable product standard or customer specification. Results are compared against declared limits to determine conformity, and a test report documents specimen details, test temperatures, aging conditions, individual and median results, and the standards applied.

Applications

High and low temperature tensile testing of sealing strips supports quality assurance and product development across multiple industries:

• Automotive: door seals, window channels, sunroof seals, trunk seals, and hood seals that must perform from arctic winters to engine-bay-level heat
• Construction: door and window weatherstrips, curtain wall gaskets, and expansion joint seals exposed to outdoor climate cycles
• Rail transit and aerospace: cabin door seals and hatch seals facing rapid pressure and temperature changes
• Appliances and HVAC: refrigerator door gaskets and oven seals requiring reliable performance at both cold and hot extremes
• Electrical enclosures: IP-rated sealing systems that must maintain sealing force across the rated operating temperature range
• Material development: comparative evaluation of new compounds, recycled content, and alternative elastomers under thermal stress

FAQ

What temperature range is typically tested?

Most automotive and architectural sealing strip specifications cover -40°C to +100°C or +150°C. EPDM compounds are commonly tested at -40°C for cold performance and aged at 70°C to 125°C for heat resistance, while silicone seals may be evaluated at temperatures up to 200°C or higher for specialized applications.

What is the difference between testing at temperature and testing after aging?

Testing at temperature measures the immediate short-term mechanical response while the specimen is hot or cold inside an environmental chamber. Testing after aging measures the permanent change in properties following prolonged thermal exposure, evaluated either at ambient temperature or at a specified test temperature. Both approaches are complementary and are frequently required together in product specifications.

Can finished sealing strip profiles be tested directly?

Yes. When the profile geometry allows, specimens are die-cut directly from the finished product, which reflects the actual manufacturing process, cure state, and material quality. When geometry is too complex, test plaques produced from the same compound and processing conditions are used as agreed between the parties.

How is retention of tensile strength calculated?

Retention equals the median aged tensile strength divided by the median original tensile strength, expressed as a percentage. The same calculation applies to elongation at break and modulus values. Comparing retention against specification limits determines whether the material passes the thermal aging requirement.

Why is elongation at break so important for sealing strips?

Sealing strips are routinely stretched during installation, joined at corners, and flexed in service. A low elongation at break, particularly after heat aging or at low temperature, indicates brittleness and a high risk of tearing or cracking, which directly compromises sealing integrity and long-term durability.