ISO 6721-6:2019

Overview

ISO 6721-6:2019 - Plastics - Determination of dynamic mechanical properties - Part 6: Shear vibration - Non-resonance method describes a forced, non-resonant test method to determine the shear complex modulus (G*) of polymers. The standard covers measurements at frequencies typically from 0.01 Hz to 100 Hz, is suited to storage moduli from 0.1 MPa to 50 MPa, and is optimized for loss-factor (tan δ) measurements > 0.02. It explains principle, apparatus, specimen preparation, test procedure, data reduction (G′, G″, tan δ), and reporting requirements.

Key topics and requirements

• Test principle: Apply sinusoidal shear force/deformation below the assembly’s fundamental shear resonance and measure force, displacement and phase angle to compute G′ (storage), G″ (loss) and tan δ.
• Frequency & modulus ranges: Typical frequency 0.01–100 Hz; reliable storage moduli ~0.1–50 MPa. Higher-frequency data can introduce significant errors.
• Apparatus essentials:
  • Shear loading assembly with rigid clamps and low thermal conductance
  • Force and displacement transducers (calibrated and traceable)
  • Electronic data-processing with specified accuracies (amplitude ±1%, phase ±0.1°, frequency ±10%)
  • Temperature control and measurement per ISO 6721-1
• Specimens: Bonded or clamped polymer specimens between metal end-pieces; dimensions and preparation per clause requirements; dimensional variation ≤ 3% recommended.
• Quality & corrections:
  • Avoid test assembly resonance (see clauses on resonance avoidance and transducer correction)
  • Apply apparatus compliance corrections if clamped/bolted connections add compliance
  • Transducer calibration accuracy: traceable and typically ±2% for minimum amplitudes
• Data handling: Calculation formulas for G′, G″ and tan δ, presentation as functions of temperature, and generation of frequency–temperature master plots using shift procedures.
• Reporting and precision: Clause guidance on precision, test atmosphere, conditioning and required test report items.

Applications and users

ISO 6721-6 is used for:

• Material R&D: characterizing viscoelastic behavior across glass–rubber transition regions
• Quality control: verifying dynamic shear properties for production batches
• Product development: evaluating damping (loss factor) and mechanical performance under cyclic shear
• Academic research: constructing master curves using frequency/temperature shift techniques Typical users include polymer testing laboratories, materials scientists, manufacturers of plastics and elastomers, instrument vendors (DMA/DMT systems), and standards/quality engineers.

Related standards

• ISO 6721-1 - General principles for dynamic mechanical properties
• ISO 6721-2 and ISO 6721-7 - Torsional deformation methods (recommended for stiffer materials >50 MPa)
• Relevant normative references are cited within ISO 6721-6 for specimen conditioning and temperature control.

Keywords: ISO 6721-6, plastics testing, shear vibration, non-resonance method, shear complex modulus, dynamic mechanical properties, tan δ, master plots.