ISO 306:1994

Plastics — Thermoplastic materials — Determination of Vicat softening temperature (VST)

Specifies four methods for the determination: method A50 using a force of 10 N and a heating rate of 50 °C/h, method B50 using a force of 50 N and a heating rate of 50 °C/h, method A120 using a force of 10 N and a heating rate of 120 °C/h, method B120 using a force of 50 N and a heating rate of 120 °C/h. The principle is determining the temperature at which a standard indenter penetrates 1 mm into the surface. The methods are applicable only to thermoplastics, for which they give a measure of the temperature at which the thermoplastics start to soften rapidly.