Overview
EN ISO 845:2009 (identical to ISO 845:2006) specifies a laboratory method for determining the apparent density of cellular plastics and rubbers. The standard covers measurement of both apparent overall density (including skins formed during moulding/extrusion) and apparent core density (after skins are removed). It applies to foamed plastics and rubbers where volume and mass can be measured; for some shaped materials a buoyancy method may be more appropriate.
Key topics and technical requirements
- Test specimens
- Minimum total specimen volume: 100 cm³.
- Minimum number of specimens: five.
- Specimens must be cut without deforming cellular structure and shaped so volume is easily calculated.
- Conditioning
- Wait at least 72 hours after manufacture before cutting specimens (may be reduced to 48 h or 16 h with supporting evidence).
- Specimens conditioned for at least 16 h in standard atmospheres or dry conditions per ISO 291.
- Standard atmospheres listed (examples): (23 ± 2) °C, (50 ± 10) % RH; alternatives at 23 °C/50 % RH or 27 °C/65 % RH.
- Apparatus & measurements
- Balance capability: 0.1 % accuracy recommended.
- Individual weighings: recorded to an accuracy of 0.5 %.
- Dimensional measurements made per ISO 1923; take at least three measurements of each dimension (five for central area of rigid boards).
- Calculation
- Density ρ (kg·m⁻³) = 10^6 × m / V (m in grams, V in mm³).
- Buoyancy correction is provided for very low-density closed-cell materials (explicit correction formula and air density values at 23 °C and 27 °C are given).
- Reporting
- Report shall include reference to the standard, material ID, conditioning conditions, presence/removal of skins, individual results, mean density, standard deviation, buoyancy corrections (if any) and any deviations from the procedure.
Applications
- Quality control and specification of cellular plastics and foams used in insulation, packaging, cushioning, automotive and construction components.
- Comparative testing in R&D to evaluate changes in foam formulation, processing or ageing affecting density.
- Supplier and contract testing where apparent overall density and apparent core density determine product performance and compliance.
Who should use this standard
- Materials test laboratories, quality engineers, product developers, foam manufacturers, and procurement teams specifying foam density requirements.
- Regulatory bodies or certification organizations needing a harmonized method for foam density measurement.
Related standards
- ISO 291 - Standard atmospheres for conditioning and testing (referenced for conditioning).
- ISO 1923 - Determination of linear dimensions for cellular plastics and rubbers (referenced for dimensional measurement).
Keywords: EN ISO 845, ISO 845:2006, apparent density, foam density determination, cellular plastics, cellular rubbers, apparent overall density, apparent core density, conditioning, buoyancy correction.
