Vicat softening point
Vicat softening temperature or Vicat hardness is the determination of the softening point for materials that have no definite melting point, such as plastics. It is taken as the temperature at which the specimen is penetrated to a depth of by a flat-ended needle with a circular or square cross-section. For the Vicat A test, a load of is used. For the Vicat B test, the load is. It is named after the French engineer Louis Vicat.
Standards to determine Vicat softening point include ASTM D 1525 and International [Organization for Standardization|ISO] 306, which are largely equivalent.
One advantage of measuring the softening point using the Vicat test rather than heat [deflection temperature] is that the Vicat is less sensitive to internal stresses introduced by processes like injection molding.
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 |
| 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