This International Standard specifies four methods for the determination of the Vicat softening temperature (VST) of thermoplastic materials: — method A50 using a force of 10 N and a heating rate of 50 K/h; — method B50 using a force of 50 N and a heating rate of 50 K/h; — method A120 using a force of 10 N and a heating rate of 120 K/h; — method B120 using a force of 50 N and a heating rate of 120 K/h. The methods specified are applicable only to thermoplastics, for which they give a measure of the temperature at which the thermoplastics start to soften rapidly.