Title: fragile glass
Long Title: IUPAC Gold Book - fragile glass
DOI: 10.1351/goldbook.12768
Status: current

Definition
Glass characterised by a large value of the fragility index (m).

Notes
1) A very fragile glass has \(m \approx 250\).
2) A fragile glass has a markedly non-Arrhenius-type temperature dependence of the viscosity and relaxation time.
3) The Vogel–Fulcher–Tammann equation can be used to describe the relaxation-time behaviour of a fragile glass.

Related Terms
- Glass: https://goldbook.iupac.org//terms/view/12773
- Vogel–Fulcher–Tammann equation: https://goldbook.iupac.org//terms/view/12819
- fragility index: https://goldbook.iupac.org//terms/view/12769
- strong glass: https://goldbook.iupac.org//terms/view/12804

Source
- PAC, 2013, 85, 1017. 'Glossary of terms relating to thermal and thermomechanical properties of polymers (IUPAC Recommendations 2013)' on page 1028 (https://doi.org/10.1351/PAC-REC-12-03-02)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/12768/html
- json: https://goldbook.iupac.org/terms/view/12768/json
- xml: https://goldbook.iupac.org/terms/view/12768/xml

Citation: Citation: 'fragile glass' 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.12768
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Accessed: 2026-04-18T06:00:25+00:00