Overview
EN ISO 11501:2004 specifies a standardized method for determining the dimensional change of plastic films and sheeting when heated. The procedure applies to films and sheets up to 1 mm thick and may be used for materials designated as thermoshrinking or not. The method supports repeatable measurement of longitudinal and transverse changes, enabling quality control, material comparison and informed processing decisions for thermoforming or shrink-film applications.
Key Topics
- Scope and conditioning: Samples are conditioned in a standard atmosphere (see ISO 291) before cutting and testing.
- Specimen dimensions: Typical specimens are approximately 120 mm × 120 mm, taken from the centre and two sides of the sheet; samples should be at least 50 mm from edges.
- Apparatus essentials:
- Circulating-air oven sized so test assemblies occupy no more than 10% of oven free volume, with provision for ≥6 air changes per hour and thermostatic control (±2 °C; ±1 °C if the test temperature is less than 100 °C).
- Metal container with a kaolin bed ~20 mm deep to support specimens during heating.
- Temperature probe immersed in the kaolin bed, stopwatch and a graduated scale capable of 0.5 mm resolution.
- Procedure summary:
- Mark longitudinal (machine) and transverse directions and central gauge lengths on each specimen.
- Measure initial gauge lengths (to 0.5 mm).
- Place specimens flat on kaolin bed in oven and heat at the specified temperature for the specified time.
- After heating, cool for at least 30 minutes in the conditioning atmosphere and re-measure gauge lengths.
- Expression of results: Percent change is calculated as (L - L0) / L0 × 100 for longitudinal and transverse directions; report mean values for three specimens, rounded to one decimal place.
- Annex A guidance: Provides example heating times and recommended temperatures for common materials (examples include recommended heating times of 5 min for non-shrink materials and 30 min for thermoshrinking/thermoforming materials, and suggested temperatures for materials such as PVC, PE, PP, PMMA and ABS).
Applications
- Quality control and batch verification of film and sheet dimensional stability.
- Process development for thermoforming, heat-sealing and shrink-film packaging.
- Material selection and comparative testing for converters, OEMs and material suppliers.
- Troubleshooting dimensional distortion during thermal processing.
Related Standards
- ISO 11501:1995 (original International Standard text adopted as EN ISO 11501:2004).
- ISO 291 - Plastics: standard atmospheres for conditioning and testing (normative reference used by EN ISO 11501:2004).
This standardized test method provides a reproducible framework for measuring thermal dimensional change of plastic films and sheeting, helping manufacturers and laboratories produce consistent, comparable data for design and process control.
