Standard Test Method for Peel or Stripping Strength of Adhesive Bonds - PDF

 

ASTM D903 covers the test method for determining the peel or stripping strength of adhesive bonds — specifically when flexible materials are bonded to rigid or flexible substrates.
It measures the force required to peel a bonded material from another at a specified angle and rate.

This standard is widely used in the adhesives industry to evaluate the performance of tapes, labels, laminates, and other adhesive-backed products.

Purpose of ASTM D903

The main objectives of ASTM D903 are:

• Determine the peel strength of adhesive bonds.

• Evaluate adhesive performance under controlled peel conditions.

• Compare different adhesive formulations or bonding processes.

• Support product quality control and material qualification.

It is typically applied to flexible-to-rigid or flexible-to-flexible bonded systems.

Equipment Required for ASTM D903 Testing

The following equipment is necessary to perform ASTM D903 testing:

• Universal Testing Machine (UTM):

  • Must be capable of applying tensile loads at a constant speed.

  • Must record force vs. displacement throughout the test.

• Peel Grips or Standard Tensile Grips:

  • Suitable grips to hold both the flexible material (peeling member) and the substrate securely.

  • Grips must avoid slippage without damaging the materials.

• Test Fixture (Optional for Rigid Samples):

  • A table or support surface may be needed to align and support rigid substrates properly.

• Measurement Devices:

  • Rulers or calipers to ensure specimen dimensions meet test specifications.

• Environmental Conditioning Equipment (Optional):

  • Ovens, chambers, or humidity cabinets to precondition samples where required.

Specimens

• Typically consists of a flexible adherend bonded to either another flexible or a rigid adherend.

• Width of the test strip is usually 1 inch (25 mm) unless otherwise specified.

• Specimens are prepared with clean, straight edges and consistent bonding conditions.

• The bonded assembly may require a curing or conditioning period before testing, depending on adhesive type.

General Test Procedure for ASTM D903

1. Specimen Preparation:

   • Prepare a bonded specimen of defined dimensions.

   • Precondition if necessary.

2. Mounting:

   • Secure the substrate in a lower grip (or to a fixed base if rigid).

   • Insert the flexible peeling material into the upper grip.

3. Test Setup:

   • Align the peeling angle at approximately 180 degrees unless otherwise specified.

   • Set the crosshead speed, typically 2 inches per minute (50 mm/min) unless specified differently.

4. Testing:

   • Start the test machine.

   • Record the force required to peel the flexible adherend from the substrate.

5. Data Collection:

   • Record the average peel force over the specified peeling distance.

   • Note any anomalies like adhesive failure, cohesive failure, or substrate failure.

6. Inspection:

   • Examine and document the type of failure:

     • Adhesive failure (bond separates at adhesive/substrate interface)

     • Cohesive failure (adhesive itself tears)

     • Substrate failure (substrate material fails)

7. Reporting:

   • Report average peel strength (usually in pounds per inch or Newtons per millimeter), failure mode, and any deviations from standard procedure.

Results and Reporting

A complete ASTM D903 test report should include:

• Description of the adhesive and substrate materials

• Adhesive application method and curing conditions

• Specimen dimensions

• Test speed and peel angle

• Average peel strength

• Observed failure mode(s)

• Environmental conditions during testing

• Any deviations from standard procedure

Related ASTM and Similar Standards

Several other ASTM standards are closely related to peel and adhesive strength testing:

• ASTM F88 – Standard Test Method for Seal Strength of Flexible Barrier Materials:
  Focuses on peel testing of seals (often heat seals) in flexible packaging.

• ASTM D1876 – Standard Test Method for Peel Resistance of Adhesives ("T-Peel Test"):
  Measures the peel resistance between two flexible bonded substrates arranged in a T-configuration.

• ASTM D3330 – Standard Test Method for Peel Adhesion of Pressure-Sensitive Tapes:
  Specifically designed for testing tapes and labels.

• ASTM D5170 – Standard Test Method for Peel Strength ("Floating Roller" method):
  Used for pressure-sensitive adhesives in specialized cases where standard peel fixtures are insufficient.

• ISO 8510-1 and ISO 8510-2 – Adhesives — Peel test for flexible-bonded-to-rigid test specimens:
  International equivalents for 180-degree peel tests.

Applications of ASTM D903 Testing

ASTM D903 peel testing is crucial in industries like:

• Automotive (interior trim adhesives)

• Aerospace (bonded panels, films)

• Construction materials (membranes, flashing tapes)

• Medical devices (wound dressings, tapes)

• Consumer goods (labels, packaging seals)

It ensures adhesive systems meet the performance expectations needed for product reliability and safety.

Conclusion

ASTM D903 is the foundation method for evaluating the peel strength of adhesive bonds, especially when flexible materials are involved.
Using proper grips, machines, and sample preparation techniques ensures accurate and meaningful results.
Standards like ASTM D1876 and ASTM D3330 offer complementary testing procedures for different adhesive system configurations.