ISO 14616 Thermal Shrinking and contracting forces test of heat shrinkable films, Film thermal shrinkage test

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ISO 14616 | Heat Shrink Film Shrinkage & Contraction Stress Tester | UnitedTest

UnitedTest manufactures professional, fully compliant ISO 14616 shrinkage stress testers for precise performance testing of polyethylene heat-shrinkable films, ethylene copolymers, and blended shrink film materials.

ISO 14616 is the global standard dedicated to plastics heat shrink film testing, specializing in quantifying two critical mechanical properties of PE-based shrink films: shrinking stress (hot shrink stress) and contraction stress (cold clamping stress). Beyond core stress indicators, this standard also supports auxiliary shrinkage ratio measurement for fast material comparison, though it is not designated as the official reference method for shrinkage ratio testing.

Engineered for packaging film R&D and quality control, our ISO 14616 compliant test machine delivers accurate, repeatable hot and cold stress data to evaluate the shrink performance and structural stability of industrial heat-shrink films.

Test Principle

A flat, tension-free film specimen is clamped to a force sensor and displacement transducer.

A vertically movable heating hood rapidly raises the specimen to a defined reference shrink temperature, releasing internal oriented residual stress generated during film extrusion and stretching manufacturing.

During heating, the film generates shrinking force (Fᵣ) as residual stress releases; the peak value of Fᵣ is recorded.

After the shrinking force drops 15%–30%, lift the heating hood and expose the specimen to ambient air (23 °C ± 2 °C) for natural cooling.

During cooling, the film produces a much larger contracting force (Fᶜ); its maximum value is captured.

A multi-channel data acquisition system continuously records real-time reference air temperature, force, displacement and time throughout heating and cooling phases. Recorded curves determine optimal thermal shrink processing parameters for the film.

ISO 14616 Thermal Shrinking and contracting forces test of heat shrinkable films

Test Specimen Requirements

Directions: lengthwise (machine direction) and crosswise (transverse direction); test at least 10 specimens per direction

Width: 15 ± 0.5 mm

Effective length between jaws: 100 mm

Thickness: mean of 3 measurements along the specimen, to nearest 1 µm

Biaxially oriented vs. uniaxially oriented films are both covered.

ISO 14616 Thermal Shrinking and contracting forces test required Test Equipment

Recomend UnitedTest Film Heat Shrinkage Tester:

Vertically mobile heating hood	Equipped with heating elements and temperature regulator to stabilize test air temperature; must calibrate correlation curves between hood setpoint and actual reference temperature θᵣ regularly. (calibration range: 100–230 °C typical).
T-shaped mounting bracket	For flat, straight fixture of film specimens without pre-tension.
Thermocouple probe	Max diameter 1.5 mm, temperature accuracy ±2 °C; probe tip positioned 5 mm beside the specimen midpoint to measure reference temperature θᵣ (read at 45 s after hood closure).
Measuring parts	Force meter: Measuring range ≥ 20 N, accuracy ±2% FS, to capture shrinking force Fᵣ and contracting force Fᶜ. Displacement transducer: Displacement measurement accuracy ±1 mm, used to calculate post-shrink length change for shrinkage ratio. Multi-channel data acquisition device: Real-time continuous logging of time, force, displacement and temperature signals.

Test Parameters:

Critical Temperature Parameter: Reference Temperature θᵣ

Definition: Air temperature measured by the thermocouple 5 mm from the specimen at exactly 45 s after lowering the heating hood.

Default baseline setting: θᵣ = 200 °C ± 3 °C if no product specification defines target temperature.

Adjustment rule: If peak shrinking force appears in <15 s heating, lower θᵣ by 10 °C increments; if no peak Fᵣ after 30 s heating, raise θᵣ by 10 °C steps. Target window for peak Fᵣ: 15–30 s of heating exposure.

5.2 Force Metrics

Shrinking force Fᵣ (N): Peak tensile force generated when heating unlocks manufacturing residual orientation stress; low Fᵣ corresponds to high free shrinkage, enabling gentle wrapping around packaged loads.

Contracting force Fᶜ (N): Maximum force generated during air cooling after heating; Fᶜ is significantly higher than Fᵣ and provides permanent clamping tightness on goods.

Complete Test Procedures of ISO 14616 Thermal Shrinking and contracting forces test of heat shrinkable films

Step 1: Specimen Mounting

Fix the flat, straight specimen on the T-bracket and force meter with zero initial tension; test lengthwise direction first for easier curve signal development.

Step 2: Temperature Setup

Use pre-established hood temperature correlation curve to set regulator to reach target θᵣ (default 200 °C ±3 °C).

Step 3: Heating & Shrinking Force Recording

Lower the hood, start timer and data logging. The moment force peaks equals the film’s shrink activation temperature; record peak Fᵣ. Once Fᵣ drops 15%–30%, lift the hood and log heating time.

Step 4: Cooling & Contracting Force Recording

Continue logging force data during natural air cooling; capture the maximum contracting force Fᶜ generated in the cooling stage. Adjust θᵣ and repeat test if peak Fᵣ falls outside the 15–30 s heating window.

Step 5: Shrinkage Ratio Measurement (Auxiliary)

Re-mount specimen between the bracket arm and displacement transducer (100 mm effective length), run heating/cooling under identical θᵣ conditions. Record final displacement after full cooling to calculate dimensional shrinkage ratio. This measurement can run simultaneously with force testing if equipment supports dual-channel logging.

Industrial Application Fields

This standard targets polyethylene-based heat-shrink film manufacturing and end-use packaging sectors:

Primary production: LDPE, LLDPE, EVA copolymer heat-shrink film factories for quality control of blown/cast oriented shrink film.

Packaging industry: Food shrink wrapping, beverage bundle packaging, logistics pallet stretch-shrink wrapping, industrial goods consolidation packaging, protective shrink packaging for metal/electronic components.

R&D laboratories: Development of new ethylene copolymer shrink film formulations, comparison of orientation process parameters, optimization of shrink tunnel heating temperature for packaging lines.

Auxiliary application: Qualification testing of non-PE heat-shrink films when customized heating parameters are validated.

Related Standard:

ASTM D2732	Standard Test Method for Unrestrained Linear Thermal Shrinkage of Plastic Film and Sheeting. focused solely on dimensional shrinkage percentage with no force/stress measurement capability, analogous to ISO 11501 rather than ISO 14616.
ASTM D1042	Standard Test Method for Linear Dimensional Changes of Plastics Caused by Exposure to Heat and Moisture
ISO 11501	Plastics Film and sheeting Determination of dimensional change on heating. ISO 11501 is the reference standard for shrinkage ratio, measuring only dimensional length change without capturing shrink/contract force.
GB/T 12027	Plastics--Film and sheeting--Determination of dimensional change on heating
GB/T 13519	Polyethylene heat-shrinkable film for packaging applications
ES 4395	Plastics-Film and sheeting - determination of dimensional change on heating.
ISO 14616	Plastics - Heat shrinkable films of polyethylene, ethylene copolymers and their mixtures - Determination of shrinkage stress and contraction stress
GB/T 34848	Determination of shrinkage character for heat-shrinkable films.
DIN 53369	Testing of plastic films; determination of the shrinking stress. key difference: DIN 53369 defines contracting force as equilibrium force after 20 minutes cooling, while ISO 14616 records the maximum transient contracting force during the cooling phase.
DIN 53377	Testing Plastic Films to Determine Dimensional Stability

Keywords: UnitedTest ISO 14616 tester, heat shrink film shrinkage stress tester, polyethylene shrink film contraction stress test machine, ISO 14616 ethylene copolymer shrink film test equipment, hot shrink cold clamping stress analyzer, PE heat shrink film shrinkage ratio testing instrument

Integrated Film Thermal Shrinkage Performance Tester, simultaneously captures real-time test data including temperature, thermal shrinkage force, residual shrinkage force and shrinkage displacement, Conform with ISO 14616, DIN 53369, ASTM D2732 as a shrink force tester or comprehensive shrink tester

Professional film heat shrink tester is precision lab equipment engineered to evaluate thermal shrinkage characteristics and thermal dimensional stability of diverse raw materials, including plastic films. compliant with international testing standards ASTM D2732 and ISO 11501.

Suitable to measure various kinds of plastic pipe or plastic materials size change after heating, or used to heat the test sample. It can be used as a heating oven as well.

Q1: What is the core purpose of ISO 14616 compared to other shrink film standards like ISO 11501?

A1: ISO 14616 mainly measures shrinking force/stress (hot stage) and contraction force/stress (cooling stage) of PE heat-shrink films. It can only assess shrinkage ratio as an auxiliary index. ISO 11501 is the official reference standard purely for measuring dimensional shrinkage rate, with no function to test shrink force or clamping force. The two standards are complementary: ISO 14616 evaluates mechanical clamping performance, ISO 11501 measures dimensional shrink magnitude.

Q2: Why is ISO 14616 testing essential for polyethylene heat-shrink films?

A2: Two core practical reasons:

Functional performance judgement: Low shrinking force lets the film softly attach to irregular goods without rupture during heating; high contraction force after cooling tightly locks bundles/pallets to avoid shifting in logistics. The test quantifies both forces numerically instead of subjective visual judgement.

Production & process optimization: Shrink stress directly reflects residual orientation stress generated during film extrusion and stretching. Deviations of shrink/contraction stress data reveal unstable manufacturing parameters (draw ratio, stretching temperature, film thickness). Test curves also help packaging factories set optimal heating tunnel temperature and dwell time to reduce film waste.

Q3: What materials does ISO 14616 apply to, and can it test non-PE shrink films?

A3: The standard’s primary scope covers polyethylene, ethylene copolymers (EVA, LLDPE blends) and their compound heat-shrinkable films. Under customized, stable operating temperatures and calibrated equipment, the test method can be extended to other thermoplastic shrink films, but the default reference temperature (200°C) is only validated for ethylene-based materials.

Q4: What are the differences between uniaxially oriented and biaxially oriented film testing under ISO 14616?

A4: Testers must prepare minimum 10 specimens separately for lengthwise (machine direction) and crosswise (transverse) directions:

Uniaxial film: Most shrink force and contraction stress concentrate on the machine direction; transverse force values will be extremely low.

Biaxial film: Both directions show obvious shrink and contraction forces.

Testing both directions distinguishes film orientation grade, which is critical for matching packaging scenarios (pallet bundling vs. all-round food wrapping).

Q5: What is reference temperature θᵣ, and why must we calibrate the correlation curve between hood setting and θᵣ regularly?

A5: Reference temperature θᵣ is the air temperature detected by the thermocouple 5 mm beside the specimen, measured exactly 45 seconds after covering the heating hood. It represents the real temperature the film specimen receives, rather than the display value of the heater regulator.

Heating hoods have environmental drift, heater aging and uneven cavity temperature. The correlation curve converts equipment setpoint to actual specimen temperature. Regular calibration prevents inaccurate heating conditions, which will cause invalid shrink force peak time and wrong stress results. The typical calibration temperature range is 100°C–230°C.

Q6: How to adjust the reference temperature if the peak shrinking force appears too fast or too slow?

A6: The target time window for the maximum shrinking force peak is 15–30 seconds after heating starts:

Peak appears <15 s: The temperature is too high; reduce θᵣ by 10°C each step and retest until meeting the time window.

No peak after 30 s heating: The temperature is too low; raise θᵣ by 10°C each step and retest.

Too fast heating causes instant over-shrinkage and inaccurate force readings; slow heating cannot fully release residual orientation stress inside the film.

Q7: What is the difference between shrinking force Fᵣ and contracting force Fc?

A7: Shrinking force Fᵣ: Generated during heating when the film’s manufacturing residual stress releases. It is a relatively small force that enables gentle conforming to product surfaces.

Contracting force Fc: Generated during open-air cooling (23°C ±2°C) after heating. Its maximum value is far larger than Fᵣ, which provides permanent tight fastening to fix packaged loads.

Both forces are converted into shrinkage stress and contraction stress by dividing with specimen cross-sectional area.

Q8: What specimen specifications are mandatory in ISO 14616?

A8: Quantity: At least 10 specimens for machine direction, another 10 for transverse direction.

Dimensions: Specimen width = 15 mm ±0.5 mm; effective clamping length between jaws = 100 mm.

Thickness: Measure three evenly spaced points on each specimen with a 1 μm precision thickness gauge, use average thickness to calculate cross-section area S.

Pre-treatment: Specimens must be flat, wrinkle-free and mounted without any initial tensile load before testing.

Q9: Can ISO 14616 test data be used for cross-laboratory comparison of film performance?

A9: No. The standard clearly states there is no available inter-laboratory round-robin test data to verify the method’s cross-lab precision. This test method is only valid for internal comparative testing within one single laboratory. Enterprises cannot rely on ISO 14616 raw stress values to compare film quality tested by different third-party labs.

Q10: Why do we lift the heating hood when shrinking force drops 15%–30% from its peak value?

A10: When Fᵣ falls 15%–30%, most of the film’s residual orientation stress has been released. Removing the hood at this stage stops further heating and triggers the cooling phase to capture the maximum contraction force accurately. If the hood stays heated longer, the film will over-relax, and the measured contraction force will be artificially low, failing to reflect real cold clamping performance in actual packaging lines.

Q11, Importance of ISO 14616 Testing for Heat-Shrink Film Materials?

A11, Characterize core packaging functionality balance

Low shrinking force (Fᵣ) allows the film to conform gently around irregular product shapes without tearing during heating; high contracting force (Fᶜ) creates permanent tight clamping after cooling to prevent loose shifting of palletized or bundled goods. ISO 14616 quantifies both properties simultaneously to balance wrapping conformability and load stability.

Manufacturing process quality control

Film orientation (uniaxial/biaxial), stretching draw ratio, and annealing temperature directly alter residual stress. Changes in σᵣ and σᶜ indicate drift in extrusion/stretching production parameters, enabling real-time adjustment of film manufacturing lines to maintain consistent shrink performance.

Optimize downstream packaging equipment parameters

The recorded temperature-force-time curves identify the optimal shrink tunnel temperature and heating dwell time for a specific film grade, reducing production waste (film breakage, insufficient wrapping, over-shrink deformation).

Formulation development benchmarking

When modifying PE copolymer resin blends, additives, or film thickness, σᵣ and σᶜ provide objective numerical data to compare shrink performance of different formulations, replacing subjective visual wrapping evaluation.

Product specification validation for end users

Packaging converters and brand owners can use standardized ISO 14616 stress values to define film purchasing specifications, ensuring uniform load-securing performance across different film suppliers.

Distinguish uniaxial vs. biaxial shrink film performance

Separate testing along machine and transverse directions quantifies directional shrink stress differences, critical for applications requiring balanced two-way shrinkage (e.g., food overwrap) vs. unidirectional pallet bundling shrink film.

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