ISO 11501:1995

Overview

ISO 11501:1995 specifies a laboratory method for determining the dimensional change on heating of plastics film and sheeting (up to 1 mm thick). The test measures changes in the longitudinal (machine) and transverse directions after controlled heating on a kaolin bed in a circulating-air oven. The procedure applies to both thermoshrinking/thermoforming materials and non‑shrink films, and is used to express shrinkage or elongation as a percentage change in gauge length.

Key topics and requirements

• Scope: Films and sheets up to 1 mm thick; measurement of dimensional change in longitudinal and transverse directions.
• Specimens: Three specimens ~120 mm × 120 mm, cut from centre and sides, with samples taken at least 50 mm from sheet edges; conditioned per ISO 291 prior to testing.
• Apparatus:
  • Circulating-air oven with minimum six air changes per hour; oven temperature controlled to keep test assembly within ±2 °C (±1 °C if specified temperature < 100 °C).
  • Metal container with a kaolin bed (~20 mm depth) sized to hold specimens flat without deformation.
  • Temperature-measuring device (probe immersed in kaolin), graduated scale (0.5 mm resolution), stopwatch.
• Procedure:
  • Mark longitudinal and transverse gauge lengths, measure initial lengths (L0, T0).
  • Heat specimens on kaolin bed for specified time and temperature.
  • After heating, cool specimens at least 30 minutes in the conditioning atmosphere and remeasure lengths (L, T).
  • Calculate percentage change: ΔL = (L − L0) / L0 × 100 (similarly ΔT).
• Reporting: Include reference to ISO 11501, material identification, test temperature and heating time, mean percentage change, direction of change, and test date.
• Annex A (informative): Provides example heating times (e.g., 5 min for non‑shrink films; 30 min for thermoshrinking/thermoforming) and recommended temperatures for common polymers (PVC, PE, PP, ABS, PMMA, cellulose acetate).

Applications and users

ISO 11501 is used to:

• Verify thermal dimensional stability for packaging films, shrink films, thermoformed parts and industrial sheets.
• Support quality control, material comparison, and supplier specifications for converters, film producers, and materials laboratories.
• Evaluate material suitability for processes involving heat (shrink tunnels, thermoforming ovens, heat-sealing).

Primary users:

• Plastics testing laboratories, quality engineers, R&D teams, converters (packaging, thermoforming), and standards/ compliance professionals.

Related standards

• ISO 291 - Standard atmospheres for conditioning and testing plastics (referenced for specimen conditioning).

Keywords: ISO 11501:1995, dimensional change, plastics film and sheeting, thermal shrinkage, kaolin bed, circulating-air oven, gauge length, thermoforming test.