Overview
ISO 23900-5:2015 specifies a laboratory method - the filter pressure value (FPV) test - for assessing the degree of dispersion (dispersibility) of pigments and extenders in thermoplastic polymers. The method is intended for colour concentrates used in extrusion and melt‑spinning processes. FPV is measured as the pressure increase generated at a defined screen‑pack during melt extrusion and provides a quantitative indicator of agglomerates or poorly dispersed particles in a polymer melt.
Keywords: ISO 23900-5, filter pressure value test, dispersibility in plastics, pigments and extenders, colour concentrate testing.
Key topics and technical requirements
- Principle: A test mixture (colour concentrate + basic test polymer) is extruded through a defined screen‑pack; the pressure difference between start and maximum pressure in front of the screen‑pack is used to calculate the FPV.
- Materials:
- Colour concentrate: homogeneous preparation of a colorant in a thermoplastic polymer.
- Basic test polymer: agreed grade/type (development work was carried out in polypropylene).
- Test mixtures:
- Mixture 1 - 200 g total with 5.0 g colorant (2.5%) for colour pigments.
- Mixture 2 - 1 000 g total with 80.0 g colorant (8%) for white and carbon black pigments.
- Apparatus:
- Single‑screw extruder (19–30 mm diameter, L/D 20–30) with non‑grooved barrel and screw without dispersing elements.
- Melt pump (constant throughput ~50–60 cm3/min) and melt pressure transducers (resolution 0.1 bar). Maintain melt pressure (controller) typically 30–60 bar to ensure pump fill.
- Screen‑packs as defined filter media (screen diameter ≈ 33.8 mm) with specific multi‑layer constructions; breaker plate to define free area; sealing ring specifications given.
- Pressure transducer accuracy typically ±1% with repeatability