The temperature at which a thermoplastic material reaches a specific degree of softness, as measured by a standardized indentation test. Exact value is mainly only meaningful when comparing two materials.
The ASTM D1525 test for this property is largely equivalent to the ISO 306 test. Vinyl-based plastics are poorly suited for this test because they tend to have a wide Vicat softening range.
Also called "Vicat Hardness" or "Vicat Softening Temperature".
ASTM D1525, Standard Test Method for Vicat Softening Temperature of Plastics.