Overview
EN ISO 6721-1:2019 - Plastics: Determination of dynamic mechanical properties - Part 1: General principles defines the core terminology and general principles used across the ISO 6721 series for measuring the dynamic mechanical (viscoelastic) properties of rigid plastics. The standard covers testing within the region of linear viscoelastic behaviour and establishes the common framework for methods that determine storage modulus, loss modulus, damping and related dynamic properties.
Key topics and technical requirements
- Scope and definitions: Clear definitions of terms and the limits of applicability (rigid plastics, linear viscoelastic region).
- Principle: Fundamental concepts for oscillatory testing and interpretation of viscoelastic responses (storage and loss moduli, transition regions).
- Test apparatus: General requirements for mechanical, electronic and recording systems; temperature-controlled enclosures; gas supply and measurement devices.
- Specimens: Guidance on specimen shape, dimensions, preparation and conditioning to standard atmospheres.
- Test procedure variables: Guidance on mounting, temperature variation, frequency and dynamic-strain amplitude control.
- Data expression and reporting: How to present moduli, damping and related results, and required test-report content.
- Precision and annexes: Notes on measurement precision and informative annexes (resonance curves; deviations from linear behaviour).
Important technical note included in the standard: different deformation modes (tensile, flexural, torsional, shear, wave propagation, etc.) can produce non-comparable results. For example, tensile-vibration tests produce uniform stress through thickness, while flexural tests preferentially sample surface regions; values are comparable only at linear strain levels and for homogeneous specimens.
Practical applications and users
EN ISO 6721-1:2019 provides the foundational principles used by:
- Materials and plastics engineers conducting dynamic mechanical analysis of polymers
- Test laboratories and QA/QC departments standardizing viscoelastic testing
- Product designers evaluating temperature- and frequency-dependent stiffness and damping
- Researchers studying polymer transitions, sound/vibration damping and performance under oscillatory loads
Practical uses include characterizing glass-transition behaviour, establishing temperature/frequency dependence of stiffness, and estimating damping for vibration or acoustic applications in automotive, aerospace, electronics and consumer products.
Related standards
Part 1 is the general-principles document for the ISO 6721 series. Normative references and method-specific parts include:
- ISO 291 (conditioning/standard atmospheres)
- ISO 4593 (thickness measurement)
- ISO 6721-2 through ISO 6721-10 (torsion-pendulum, flexural resonance, tensile vibration, shear, torsional, wave-propagation, sonic-pulse and other method-specific procedures)
Using EN ISO 6721-1:2019 ensures consistent terminology, test-report content and interpretation across dynamic mechanical property tests for plastics.
