ISO 6721-1:2019

Overview

ISO 6721-1:2019 - Plastics - Determination of dynamic mechanical properties - Part 1: General principles defines the common principles, definitions and requirements that apply across the ISO 6721 series for measuring the dynamic mechanical properties of rigid plastics in the linear viscoelastic region. It establishes terminology (e.g., complex modulus, storage modulus, loss modulus, phase angle) and describes the aspects shared by individual test methods (torsion, flexural, tensile, shear, wave propagation, rheometry, etc.). The standard emphasizes that different deformation modes (tensile, flexural, torsional) can yield non‑directly comparable results unless test conditions and specimen homogeneity are controlled.

Key Topics

• Definitions and theory: clear definitions of complex modulus M*, storage modulus M′, loss modulus M″ and phase angle δ, and relationships between moduli for isotropic materials.
• Principles of measurement: general measurement concepts for sinusoidal and resonant methods, limits of linear viscoelastic assumptions and implications for data interpretation.
• Test apparatus requirements: guidance on mechanical, electronic and recording systems, temperature‑controlled enclosures, gas supply and dimensional measurement devices.
• Specimens and preparation: general requirements for specimen shape, dimensions, preparation, conditioning (reference to ISO 291 for atmospheres) and required number of specimens.
• Test procedure: common procedural requirements including test atmosphere, cross‑section measurement, specimen mounting, and controlled variation of temperature, frequency, and dynamic strain amplitude.
• Data handling: expression of results, precision statements, required test report contents and informative annexes (resonance curves; deviations from linear behaviour).
• Normative references: links to other parts of ISO 6721 (Parts 2–10 and 12) and related standards (e.g., ISO 4593).

Applications and Users

ISO 6721-1:2019 is foundational for anyone conducting dynamic mechanical analysis (DMA) or vibration/damping evaluations of plastics. Typical users include:

• Materials scientists and polymer researchers performing viscoelastic characterization.
• Test laboratories and quality‑control teams validating material properties for specifications.
• Product developers in automotive, aerospace, electronics and construction assessing performance under temperature and frequency changes.
• Acoustic and vibration engineers estimating damping and sound transmission in polymer or polymer‑metal systems.
• Standards and compliance professionals preparing test reports for procurement, certification or regulatory documentation.

This part ensures consistent terminology and shared test principles so that results reported under different ISO 6721 methods are transparent and comparable when test conditions and specimen homogeneity are clearly documented.

Related Standards

• ISO 6721 series: Parts 2–10, 12 (torsion, flexural, tensile, shear, wave‑propagation, rheometry, etc.)
• ISO 291 - Standard atmospheres for conditioning and testing
• ISO 4593 - Determination of thickness by mechanical scanning

Keywords: ISO 6721-1:2019, dynamic mechanical properties, plastics, viscoelastic, complex modulus, storage modulus, loss modulus, DMA, tensile, flexural, testing standards.