Title: percolation threshold
Long Title: IUPAC Gold Book - percolation threshold
DOI: 10.1351/goldbook.08848
Status: current

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.

Related Term
- Electrically conducting polymer composites: https://goldbook.iupac.org/terms/view/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)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/08848/html
- json: https://goldbook.iupac.org/terms/view/08848/json
- xml: https://goldbook.iupac.org/terms/view/08848/xml

Citation: 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. 10.1351/goldbook.08848
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Accessed: 2026-06-24T16:02:47+00:00