Overview
ISO 171:2022 - Plastics - Determination of bulk factor of moulding materials specifies a standard method to determine the bulk factor of moulding materials. The bulk factor is defined as the ratio of the apparent volumetric density of a given quantity of particles to the material density. This value is used in mould design and material handling to relate particle packing to the true density of the polymer.
Key topics and requirements
- Definition: Bulk factor = apparent volumetric density / material density.
- Principle: The bulk factor enables calculation of minimum cavity volume in mould design by linking loose-particle packing to solid material density.
- Test conditions: Determinations must be performed at one of the test temperatures specified in ISO 291 (standard atmospheres for conditioning and testing).
- Apparent volumetric density: Measured for the particulate form of the moulding material using either ISO 60 (pourable materials, funnel method) or ISO 61 (non-pourable materials).
- Material density: Determined in accordance with the ISO 1183 series (methods for density of non-cellular plastics).
- Calculation and reporting: The bulk factor is calculated from the two independently measured densities. The standard also specifies required items in the test report, including:
- reference to ISO 171:2022
- material identification and test temperature
- measured apparent volumetric density and material density
- calculated bulk factor
- deviations, unusual observations, and test date
Applications and who uses it
ISO 171:2022 is directly relevant for:
- Mould designers and toolmakers - use the bulk factor to estimate minimum cavity volume and optimize mould size.
- Materials laboratories and QA/QC teams - perform standardized measurements for material specifications and batch acceptance.
- Polymer compounders and suppliers - provide consistent bulk factor data to customers for processing and tooling calculations.
- Production engineers - plan feed-hopper capacity, shot weight, and handling logistics based on particle packing characteristics.
Practical benefits include improved accuracy in mould cavity design, consistent material specification across suppliers, and reduced trial-and-error during tool commissioning.
Related standards
- ISO 60 - Apparent density of pourable materials (funnel method)
- ISO 61 - Apparent density of non-pourable moulding materials
- ISO 1183 (all parts) - Density determination of non-cellular plastics
- ISO 291 - Standard atmospheres for conditioning and testing
Using ISO 171:2022 alongside these referenced methods ensures consistent, reproducible bulk factor measurements for plastics processing and mould design.