Overview - ISO 4651:1988 (Cellular rubbers and plastics - Determination of dynamic cushioning performance)
ISO 4651:1988 specifies a laboratory method to determine the dynamic cushioning performance of cellular rubbers and rigid or flexible cellular plastics used in packaging. The standard measures the peak deceleration of a drop hammer impacting a test piece and is intended primarily for quality assurance. Annex A provides notes to consider if the test is used to obtain design data (e.g., cushioning diagrams and dynamic compressibility).
Key topics and technical requirements
- Test scope: Applicable solely to materials used in packaging; focuses on peak deceleration and displacement during impact.
- Specimen geometry: Test pieces typically 150 mm × 150 mm × 50 mm (±5 mm). Ten specimens minimum; thickness and density uniformity limits apply.
- Conditioning: Samples tested at least 72 h after manufacture and conditioned (e.g., 23 °C ± 2 °C, 50 % ± 5 % RH) per referenced ISO standards.
- Drop apparatus: Flat-based drop hammer on an anvil (anvil mass ≥ 100× hammer mass) - guided vertical drop tester preferred for high decelerations; pendulum tester acceptable for low stresses.
- Impact velocities: Standard equivalent drop heights of 250 mm and 750 mm (1 250 mm optional). Impact velocity must be ≥ 95 % of free-fall value.
- Static stress: Five static stress levels recommended (chosen so one gives minimum peak deceleration and others ±10–20 %). Fewer stresses may be agreed by supplier/purchaser.
- Measurements: Record deceleration–time pulses and displacement; measure peak deceleration on first and third impacts of three successive impacts per specimen. Correct peak deceleration for any deviation from 50 mm reference thickness.
- Instrumentation: Transducers (piezoelectric or strain-gauge) and recorders with adequate frequency response are required. Decelerometer natural frequency and amplifier time-constant requirements are specified to limit measurement error to ±5 %.
- Outputs: Peak deceleration, corrected peak deceleration, displacement curves, dynamic compression diagrams and cushioning diagrams (see Annex A for design-use notes).
Applications and who uses it
- Packaging engineers and product designers selecting or validating cushioning foams and cellular plastics.
- Manufacturers performing routine quality assurance on cellular rubber/plastic cushioning.
- Test laboratories providing standardized impact-response data for packaging materials.
- Procurement teams and purchasers specifying performance requirements for protective packaging.
Related standards
Normative references cited in ISO 4651:1988 include:
Keywords: ISO 4651:1988, dynamic cushioning performance, cellular rubbers and plastics, drop hammer test, peak deceleration, packaging materials, quality assurance, cushioning diagram.
