Dynamic Thermo-Mechanical Analysis (DTMA) according to ASTM D5026 and ISO 6721

Test Principle:

ASTM D5026 outlines a method for determining the dynamic mechanical properties of plastic materials when subjected to oscillating tensile forces. The test measures how the material responds to sinusoidal stress over a range of temperatures and/or frequencies, providing insight into stiffness, damping, and viscoelastic behavior.

Test Method Summary:

• Sample Preparation:
  • Test specimens are typically rectangular bars or dumbbell-shaped, prepared according to the standard's dimensions and guidelines.
• Test Setup:
  • A Dynamic Mechanical Analyzer (DMA) is used in tensile mode.
  • The specimen is clamped at both ends and subjected to a sinusoidal tensile deformation while being heated or cooled at a controlled rate.
• Measurements:
  • The instrument measures:
    • Storage modulus (E') – reflects elastic behavior (stiffness).
    • Loss modulus (E'') – reflects viscous behavior (energy dissipation).
    • Tan δ (damping factor) – ratio of E'' to E', indicating how much energy is lost as heat.
  • Data is typically collected over a range of temperatures or frequencies.
• Test Conditions:
  • Frequency range: usually 0.01 to 100 Hz.
  • Temperature range: depends on the material but commonly from -100°C to +300°C.

Purpose:

This test helps assess a plastic's performance under real-world dynamic loading conditions and is especially useful for:

• Comparing materials
• Quality control
• Predicting long-term mechanical performance

(Particularly ISO 6721-4 for tensile mode)

Test Principle:

ISO 6721 is the international counterpart to ASTM D5026, detailing methods for determining dynamic mechanical properties using sinusoidal oscillation. ISO 6721 is split into parts depending on the test mode (tension, bending, shear, etc.). ISO 6721-4 specifically addresses tensile oscillation for rigid plastics.

Test Method Summary (ISO 6721-4):

• Very similar to ASTM D5026, using a DMA in tensile mode.
• The sample is subjected to periodic tensile deformation while temperature or frequency is varied.
• Measurements include:
  • Storage modulus (E')
  • Loss modulus (E'')
  • Loss factor (tan δ)
• Standard specimen size and clamp type are defined, and precision in temperature/frequency control is critical.

Purpose:

Used to evaluate the viscoelastic behavior of rigid plastics under dynamic conditions, ISO 6721 is particularly useful for:

• Identifying material transitions (e.g., glass transition)
• Predicting behavior in structural or load-bearing applications
• Comparing material performance across suppliers or formulations