Term: percolation threshold
https://doi.org/10.1351/goldbook.08848

Definition:
Minimal volume fraction of functionally active small particles evenly dispersed in a non-active matrix, at which the long-range (infinite) functional connectivity in the system is achieved.

Notes:
1) A desired transport through the composite material is not possible below the percolation threshold. Percolation threshold is about \(\pu{0.3}\) to \(\pu{0.35}\) (by volume) for composites with nearly spherical disperse particles while it can be even below \(\pu{0.10}\) for composites with short fibers, depending on the fibers’ aspect ratio (the length to diameter ratio).
2) Electrically conducting polymer composites composed of carbon black microparticles dispersed in a rubbery matrix are transposed in the electrically conducting state above percolation threshold.

Link: 
Related Term: electrically conducting polymer composites (http://doi.org/10.1351/goldbook.08798).

Source: PAC, 2022, 94, 15. 'Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)' on page 40 (https://doi.org/10.1515/pac-2020-0501)

Citation: 'percolation threshold' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08848

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