Material Testing and Performance Validation for Polyurethane Elastomers

Polyurethane components destined for demanding applications require rigorous material testing before deployment. Standard testing validates critical properties: Shore hardness (ASTM D2240), tensile strength and elongation (ASTM D412), tear resistance (ASTM D624), abrasion resistance (DIN 53516/ISO 4649), and compression set (ASTM D395). Test specimens are prepared per ASTM D3182 and conditioned at 23±2°C (73±4°F) and 50±5% relative humidity for a minimum of three hours before testing.

This systematic approach to polyurethane material testing ensures batch-to-batch consistency and provides engineers with verified data to confidently specify components for critical applications.

1. Polyurethane Material Testing: Physical Properties

Hardness Testing (ASTM D2240)

Hardness serves as the primary classification metric for polyurethane elastomers. Shore hardness testing measures resistance to indentation using a calibrated durometer with a spring-loaded indenter.

Shore A scales apply to flexible elastomers ranging from soft gels (Shore 20A) to firm industrial compounds (Shore 95A). The truncated cone indenter applies 8.05 N of force, and the penetration depth translates to a 0–100 scale reading. Shore D scales measure harder, more rigid materials using a sharper cone indenter with 44.5 N force.

Specimen thickness matters. ASTM D2240 requires a minimum 6 mm (0.24 in) thickness to prevent the support surface from influencing readings. Thinner specimens produce artificially high hardness values—a phenomenon called the “sink-in” effect. While stacking layers to reach 6 mm is permitted, a single homogeneous specimen yields more reliable results.

Standard practice calls for five readings across each specimen, with the average reported. Production tolerances typically run ±5 Shore points, though controlled processing can achieve ±3 points.

Tensile Properties (ASTM D412)

Tensile testing reveals how polyurethane behaves under stretching forces. A universal testing machine pulls dumbbell-shaped specimens at 500±50 mm/min until rupture, generating a stress-strain curve that yields three critical values:

Ultimate tensile strength indicates the maximum stress before failure. High-grade industrial polyurethanes typically range from 20 to 50 MPa (3,000–7,000 PSI).

Elongation at break measures stretch capacity as a percentage of original length. Polyurethanes exhibit exceptional elongation, often reaching 500–700% for Shore 80A–90A formulations.

Tensile modulus (specifically 100% and 300% modulus) represents the stress required to achieve those elongation levels. This metric provides a superior measure of functional stiffness compared to hardness alone.

For components subjected to cyclic loading — such as polyurethane roller coatings — tensile properties directly predict fatigue life and operational durability.

Tear Strength (ASTM D624)

Tear testing measures resistance to crack initiation and propagation—essential for components exposed to sharp impacts or edges. The test uses standardized specimen geometries:

• Die C (crescent): Most common for general elastomer evaluation
• Die B (angle): Used when sharp notch sensitivity is critical
• Die A (no nick): Measures initiation resistance without pre-cut

Results express in kilonewtons per meter (kN/m) or pounds per linear inch (PLI). A Shore 90A polyether polyurethane typically achieves 400–450 PLI tear strength—significantly outperforming natural rubber in demanding industrial environments like mining and material handling.

2. Polyurethane Performance Testing

Abrasion Resistance Testing

Abrasion resistance determines service life in wear-intensive applications. Two primary methods apply:

DIN 53516 / ISO 4649 uses a rotating drum covered with standardized abrasive paper. A cylindrical specimen (16 mm diameter, 6 mm thick) traverses the drum surface under controlled load over a 40-meter path. Results express as volume loss in cubic millimeters—lower values indicate better wear resistance.

ASTM D5963 follows essentially the same procedure with minor parametric variations, making results comparable between standards.

These accelerated tests rank materials effectively for comparison, though they don’t directly predict field performance since actual wear conditions vary significantly. For applications like conveyor scrapers or pipe-laying vessel rollers, field trials supplement laboratory data to validate material selection.

Compression Set Testing (ASTM D395)

Sealing applications demand materials that maintain shape after sustained compression. Compression set testing quantifies permanent deformation.

Method B (constant deflection) is most common: specimens compress to 75% of original thickness and hold at 70°C (158°F) for 22 hours. After releasing and allowing recovery at room temperature, the permanent set calculates as:

Compression Set (%) = (Original Thickness – Recovered Thickness) / (Original Thickness – Spacer Thickness) × 100

Lower percentages indicate better elastic memory. High-performance polyether polyurethanes achieve 15–30% compression set, making them suitable for gaskets and seals requiring long-term sealing integrity. General-purpose elastomers exceeding 50% compression set typically fail prematurely in sealing applications.

Resilience Testing (ASTM D2632)

Rebound resilience measures energy return—the ratio of energy released during recovery to energy absorbed during deformation. The vertical rebound test drops a standard plunger from a fixed height onto the specimen and measures rebound height as a percentage.

High resilience (60–80%) indicates low hysteresis and minimal heat buildup during dynamic cycling—critical for high-speed rollers and wheels. Lower resilience (30–50%) suggests better energy absorption, preferred for vibration damping and impact pads.

3. Environmental Resistance Testing

Beyond mechanical properties, environmental exposure testing validates long-term performance:

Heat aging (ASTM D573) exposes specimens to elevated temperatures (typically 70–100°C / 158–212°F) for extended periods (24–168 hours). Post-aging property retention—particularly hardness change and tensile strength retention—indicates thermal stability.

Fluid immersion (ASTM D471) measures volume and weight change after submersion in oils, fuels, or process chemicals. Results guide material selection for applications involving fluid contact.

UV and ozone resistance testing applies to outdoor applications where photodegradation and ozone cracking threaten service life.

4. Test Documentation and Reporting

Comprehensive testing generates documentation linking results to raw materials and process parameters:

• Unique lot/batch identification
• Raw material traceability (supplier lot numbers, Certificates of Analysis)
• Test date, conditions, and operator identification
• Individual measurements and statistical analysis
• Pass/fail determination against acceptance criteria

Records retention follows industry standards compliance requirements—typically five years minimum for industrial applications, with marine and offshore components often requiring ten years or longer per classification society rules.

5. In-House vs. Third-Party Testing

Routine quality control relies on in-house testing for production efficiency. Calibrated instruments, trained operators, and documented procedures ensure reliable results for incoming material verification, in-process monitoring, and final product release.

Third-party accredited laboratory testing applies when:

• Customers require independent verification
• Certification bodies mandate external testing (DNV, ABS, Lloyd’s)
• Dispute resolution requires neutral evaluation
• Specialized tests exceed in-house capabilities

Accredited laboratories operate under ISO/IEC 17025 quality systems, providing defensible results accepted globally.

6. Frequently Asked Questions

What standard tests are performed on polyurethane elastomers?

Standard testing includes Shore hardness (ASTM D2240), tensile properties and elongation (ASTM D412), tear strength (ASTM D624), compression set (ASTM D395), and abrasion resistance (DIN 53516 or ASTM D5963). Additional tests may include resilience, heat aging, and chemical resistance depending on application requirements.

How is abrasion resistance measured for polyurethane?

Abrasion resistance testing per DIN 53516 or ASTM D5963 moves a cylindrical specimen across rotating abrasive paper under controlled load. Volume loss in cubic millimeters quantifies wear resistance—lower values indicate better performance. Results enable material comparison but don’t directly predict field service life.

What is compression set and why does it matter?

Compression set measures permanent deformation after sustained compression at elevated temperature. Expressed as a percentage, lower values indicate better elastic recovery. For sealing applications, compression set below 30% typically ensures adequate long-term sealing performance, while values exceeding 50% suggest premature seal failure.

Are test certificates provided with polyurethane shipments?

Reputable manufacturers provide Certificates of Conformance documenting batch identification, material specification, and key test results. Full material test reports with complete property data are typically available upon request and required for marine, aerospace, and other certified applications.

Can custom testing be performed to specific requirements?

Beyond standard ASTM and ISO tests, many manufacturers accommodate customer-specific test protocols, application-simulating conditions, and specialized measurements. Engineers should discuss testing requirements early in the specification process to ensure documentation meets quality system needs.

Pepson has manufactured high-performance polyurethane elastomers since 1998, serving industries worldwide from our Dongguan, China facility. Our material science expertise and quality manufacturing deliver solutions optimized for demanding applications.