Overview
ISO 14616:1997 specifies a conventional laboratory method for measuring the shrinkage (shrinking) stress and contraction (contracting) stress of heat‑shrinkable films made from polyethylene, ethylene copolymers, and their mixtures. The standard defines terminology, test apparatus, specimen preparation, test procedure, and the form of results. It also permits assessment of the shrinkage ratio (dimensional change on heating), while noting ISO 11501 as the reference method for dimensional-change measurement.
Key topics and technical requirements
- Scope & purpose: Procedure to quantify forces generated when heat‑treated, oriented films shrink and contract; method may be adapted to other materials with appropriate settings.
- Definitions: Heatshrinkable film (uniaxial/biaxial orientation), shrinkage ratio, shrinking force, contracting force, reference temperature.
- Specimen preparation:
- At least 10 specimens per direction (lengthwise and crosswise).
- Width: 15 mm ± 0.5 mm; effective gauge length 100 mm.
- Thickness measured as the mean of three readings (accuracy 1 µm).
- Apparatus requirements:
- Vertically mobile heating hood with regulated air temperature.
- Force meter capable of measuring forces over a range of at least 20 N with ±2% accuracy.
- Displacement transducer (±1 mm) when measuring shrinkage ratio.
- Multichannel recorder for time, force, temperature and displacement.
- Thermocouple probe (max 13 mm diameter, ±2 °C accuracy) positioned ~5 mm from the specimen.
- Test procedure:
- Mount specimen slack on force meter; heat under hood to the shrinkage temperature.
- Record force until the maximum shrinking force appears, then continue to observe until the shrinkage force drops ~15–30% before lifting hood.
- Allow cooling in air to ambient 23 °C ±2 °C and record the contracting force peak.
- Adjust the reference temperature (typically tested in a range) so maximum shrinking occurs within 15–30 s of exposure; default starting reference often 200 °C ±3 °C when unspecified.
- Results & reporting:
- Report shrinking and contracting stresses as force divided by cross‑sectional area (Pa) and shrinkage ratio as percent decrease in length.
- Note method precision is not established by inter‑laboratory data - intended for within‑laboratory comparisons.
- Test report must include film type/origin, thickness, orientation, reference temperature, stress values, shrinkage ratio, mean and standard deviation, procedural notes and date.
Applications and users
- Film and packaging manufacturers performing quality control and process optimization for heat‑shrink packaging.
- Materials and product test laboratories assessing performance of shrink films (polyethylene and ethylene copolymers).
- R&D and process engineers evaluating orientation, sealing, and shrink behavior in protective and packaging films.
- Buyers and specification writers who require standardized test data for procurement and compliance.
Related standards
- ISO 11501 - referenced as the reference method for precise measurement of dimensional change (shrinkage ratio).
Open preview (PDF)Plastics — Heatshrinkable films of polyethylene, ethylene copolymers and their mixtures — Determination of shrinkage stress and contraction stress
