Overview
ISO 11502:2018 - "Plastics - Film and sheeting - Determination of blocking resistance" defines test methods to assess the tendency of flexible plastic films and sheets to adhere (block) to one another when placed in contact under specified temperature and light pressure. The standard provides two test methods: a qualitative method (Method A) to detect visible damage or lifting of a weight on separation, and a quantitative method (Method B) that measures the separation force in newtons using a tensile-testing machine.
Key topics and requirements
- Scope: Applies to flexible plastic films and sheeting; one qualitative and one quantitative method are specified. Alternative conditions may be used to match material type or end use.
- Specimen size and preparation: Typical specimen strips are 150 mm × 76 mm; minimum time between manufacture and testing is 16 hours; conditioning in standard atmospheres per ISO 291 for 24 hours before testing.
- Method A - Qualitative:
- Assemblies are stacked and heated at 50 °C ± 2 °C for 24 h under a pressure of 7 kPa (using 5.4 kg weights).
- Separation performed at a uniform manual rate (~25 mm/s); blocking is recorded if surface damage occurs or a metal bar (50 g or 100 g depending on print) is lifted.
- Test report must reference ISO 11502:2018, method used, specimen details, metal bar used, blocking/damage observations, and test date.
- Method B - Quantitative:
- Assemblies heated at 50 °C ± 2 °C for 3 h under 3 kPa (2.3 kg weights).
- Samples are fixed to 100 mm × 100 mm aluminium blocks in a tensile-testing machine; crosshead speed 5 mm/min, chart speed 50 mm/min.
- The machine records the maximum force (N) required to separate layers; the mean of five determinations is reported.
- Precision statement not yet established due to lack of interlaboratory data.
Applications and users
ISO 11502:2018 is used to:
- Evaluate and control blocking resistance in product development and quality control for:
- Flexible packaging films
- Agricultural films, laminates, and protective sheeting
- Printed or embossed films where surface interaction matters
- Support material selection, process adjustments, and complaint investigation by:
- Film and sheeting manufacturers
- Converters and packagers
- Testing laboratories and R&D teams
- Specification writers and procurement engineers
Related standards
- ISO 291 - Plastics: standard atmospheres for conditioning and testing (normative reference for conditioning in ISO 11502:2018).
Keywords: ISO 11502:2018, blocking resistance, plastics film testing, film and sheeting, qualitative blocking test, quantitative blocking test, blocking test methods.
