Overview
EN ISO 11502:2018 - Plastics - Film and sheeting - Determination of blocking resistance specifies two standard methods to assess the tendency of flexible plastic films and sheets to adhere (block) to one another when held in contact under defined temperature, time and light pressure. The document, adopted by CEN as EN ISO 11502:2018, provides a qualitative method (Method A) and a quantitative method (Method B) for routine laboratory evaluation of blocking resistance.
Key topics and technical requirements
- Scope: Tests blocking (unintentional adherence) of flexible plastic films and sheeting under specified conditions; one qualitative and one quantitative method.
- Conditioning reference: Uses standard atmospheres defined in ISO 291 for specimen conditioning and testing.
- Specimen dimensions and preparation: Typical specimens are strips 150 mm × 76 mm; orientation and sampling rules (e.g., machine direction, printed/embossed faces, sampling from rolls) are specified.
- Method A - Qualitative
- Assemblies are stacked between glass plates and filter paper, loaded to produce 7 kPa pressure, and held at 50 °C ± 2 °C for 24 h (default).
- After conditioning, separation is performed at a controlled rate (25 mm/s ± 2.5 mm/s) with prescribed metal bars (50 g or 100 g) used to detect lifting.
- Blocking is recorded if the metal bar lifts or if surface damage is observed.
- Test-report items are defined (reference to standard, material ID, metal bar used, damage, date).
- Method B - Quantitative
- Specimens are conditioned similarly then placed between platens in a constant-speed tensile testing machine with 100 mm × 100 mm aluminium blocks.
- The machine measures the force required to separate the stuck specimens, giving a quantitative blocking value.
- Apparatus and specimen orientation rules (longest side = machine direction) are specified; precision and reporting requirements are included.
- Flexibility: Alternative times/temperatures/pressures may be used to suit material type or end-use.
Applications and who uses it
- Quality control laboratories in film and sheet manufacturing to ensure consistent anti-block performance.
- Material R&D teams evaluating anti-block additives, coatings, surface treatments, or packaging laminates.
- Converters and printers to assess whether storage, printing or embossing will increase blocking risk.
- Packaging engineers and specifiers selecting films for roll handling, multilayer structures or sensitive printed surfaces.
- Procurement and compliance teams that require standardized test evidence for supplier acceptance.
Related standards
- ISO 291 - Standard atmospheres for conditioning and testing (normative reference).
- EN ISO 11502:2018 supersedes EN ISO 11502:2005.
Keywords: EN ISO 11502:2018, blocking resistance, blocking test, plastics film, sheeting, qualitative method, quantitative method, anti‑block, film testing.
