pakkaustiheyden

Pakkaustiheyden is a term used in Finnish to refer to packing density, the fraction of a given volume that is occupied by solid material in a packed assembly of particles. It is commonly expressed as a dimensionless volume fraction, φ = V_solid / V_total, and is related but not identical to bulk density and true density. In practice, packing density can be described by bulk density (including void space) and tapped density after compaction by tapping or vibration.

Several factors influence packing density: particle size distribution, shape, and porosity; surface roughness; moisture and cohesion; and the method used to compact the material (pouring, tapping, vibration). Monodisperse, spherical particles tend to reach higher densities under ideal packing conditions, while irregular shapes and broad size distributions often reduce density.

Common concepts connected to packing density include porosity and permeability. Porosity is the complement of packing density, with porosity ε = 1 − φ. In porous materials, packing density affects how easily fluids or gases move through the material, as well as mechanical strength, thermal and electrical properties, and processing behavior such as compaction and sintering.

Typical values for model systems: random loose packing (RLP) around 0.55; random close packing (RCP) about 0.64 for spherical particles; ideal ordered close packing (face-centered cubic or hexagonal close packing) around 0.74. For real powders, densities vary with material and preparation.

Applications: packing density is important in powder metallurgy, pharmaceuticals, ceramics, soil science, and packaging engineering. Measuring and controlling packing density helps predict flow, compaction, porosity, and performance of particulate systems.

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