Overview
ISO 8570:1991 - Plastics - Film and sheeting - Determination of cold-crack temperature specifies a repeatable impact method to assess the brittleness of plastic film and sheeting at low temperatures. The standard defines how to determine a conventional cold‑crack temperature (the temperature at which 50% of specimens break or are damaged) for finished films and sheets of a given thickness and texture. The method characterizes finished products rather than raw-material composition and is intended for comparative evaluation of low‑temperature behaviour.
Key topics and technical requirements
- Specimen preparation: Strips of 60 mm × 15 mm, edges free of defects; specimens looped with printed/textured side outward if applicable. Thickness measured per ISO 4593; conditioning per ISO 291.
- Test geometry: Specimens formed into a flattened loop and clamped on a platen; the fold location is 20 mm from the clamp.
- Impact device: Guide tube and free‑fall impact mass (typical masses: 200 g and 500 g), mass diameter 18–29 mm; guide tube ~250 mm long with internal diameter ≈ mass + 1 mm.
- Cooling and temperature control: Cooling chamber capable of stepping temperature in 5 °C increments and maintaining temperature to within ±1 °C; thermometer or thermocouple accuracy 0.5 °C.
- Procedure: Test 10 specimens per direction (machine and transverse); start with temperature where no specimen fails, then lower in 5 °C steps and apply impact; repeat until all specimens fail. If specimens fail at the starting temperature, increase temperature in 5 °C steps until no failures occur, then follow the downward sequence.
- Result expression: Cold‑crack temperature is the highest test temperature (°C) at which all specimens are broken/damaged or calculated from failure data (graphical or calculation method) where 50% failure is determined.
- Reporting: Include standard reference, material identification (thickness, manufacture date, surface type), cold‑crack temperature with impact mass in brackets (e.g., (200): −13 °C), number of specimens, failure type, and any deviations.
Applications and users
ISO 8570:1991 is used where low‑temperature brittleness of plastic film and sheeting is critical:
- Quality control and acceptance testing for packaging films, protective sheeting and industrial film products
- Product development and comparative testing for automotive, cold‑climate, and outdoor applications
- Certification labs and suppliers verifying low temperature performance and brittleness
- Regulatory and procurement specifications requiring standardized cold‑crack assessment
Related standards
- ISO 291 - Standard atmospheres for conditioning and testing (referenced for specimen conditioning)
- ISO 4593 - Determination of thickness of plastics film and sheeting (referenced for thickness measurement)
Keywords: ISO 8570:1991, cold-crack temperature, plastics film testing, low temperature brittleness, plastic sheeting, impact test, cooling chamber, ISO 4593, ISO 291.
