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Vicat softening temperature orVicat hardness is the determination of thesoftening point for materials that have no definitemelting point, such asplastics. It is taken as the temperature at which the specimen is penetrated to a depth of1 mm by a flat-ended needle with a1 mm2 circular or square cross-section. For the Vicat A test, a load of10 N is used. For the Vicat B test, the load is50 N. It is named after the French engineerLouis Vicat.
Standards to determine Vicat softening point includeASTM D 1525 andISO 306, which are largely equivalent.[1]
One advantage of measuring the softening point using the Vicat test rather thanheat deflection temperature is that the Vicat is less sensitive to internal stresses introduced by processes likeinjection molding.[2]
The Vicat softening temperature can be used to compare the heat-characteristics of different materials.
Four different methods may be used for testing.
| Method | Load | Heating rate |
|---|---|---|
| (N) | (°C/h) | |
| A50 | 10 | 50 |
| B50 | 50 | 50 |
| A120 | 10 | 120 |
| B120 | 50 | 120 |
ISO 10350 Note
ISO 10350 Vicat values are tested using the B50 method.
Similar Standards: ASTM D1525
