ISO 306 Plastics — Thermoplastic Materials — Determination of Vicat Softening Temperature (VST)

Material Testing

ISO 306 Plastics — Thermoplastic Materials — Determination of Vicat Softening Temperature (VST)

EUROLAB laboratory provides testing and compliance services within the scope of ISO 306 standard. The ISO 306 standard, developed by the International Standards Organization (ISO), specifies four methods for determining the Vicat softening temperature (VST) of thermoplastic materials. The methods mentioned are valid only for thermoplastics, where they give a measure of the temperature at which the thermoplastics begin to soften rapidly.

ISO 306 Plastics — Thermoplastic Materials — Determination of Vicat Softening Temperature (VST)

ISO 306 Test Methods:

  • Method A10 using a force of 50 N and a heating rate of 50 °C/hr
  • Method B50 using a force of 50 N and a heating rate of 50 °C/hr
  • Method A10 using a force of 120 N and a heating rate of 120 °C/hr
  • Method B50 using a force of 120 N and a heating rate of 120 °C/hr.

The temperature at which a standard recess tip with a flat point under a standard load penetrates 1 mm into the surface of the plastic test specimen is determined. While the sample is heated at a certain and uniform rate, the indentation tip exerts a certain force perpendicular to the test sample. The temperature of the sample in degrees Celsius, measured as close as possible to the recessed area at 1 mm penetration, is indicated as VST.

The apparatus essentially consists of a rigid metal frame in which a rod can move freely in the vertical direction. A weight bearing plate is attached to one end of the bar and a recess end to the other. The base of the frame is equipped with a support plate or other suitable load application device.

It is recommended that the inlet bar and frame(s) be made of materials with low thermal expansion. Unless the vertical parts of the apparatus have the same linear coefficient of thermal expansion, the difference in the length change of these parts during testing will cause an error in reading the apparent penetration of the test specimen.

A blank test should be performed on each instrument in the calibration using a test specimen made of rigid material with a low coefficient of expansion and a thickness comparable to that of the specimen under test. The blind test should cover the temperature ranges to be used in the actual determination and a correction term should be determined for each temperature. If the correction term is 0,02 mm or greater, its value and algebraic sign should be recorded; and the term applied to each test result by algebraically adding to the reading of the apparent penetration of the test sample. Invar and borosilicate glass were found suitable as materials for the test specimen in the blank test.

It must be made of hardened steel of at least 2 mm in length, circular cross-section and (1.000 ± 0.015) mm² (corresponding to a recess tip diameter of (1.128 ± 0,008) mm) and fixed at the bottom. reed. The indentation should be perpendicular to the bar when in contact with the sample. The tip should be free of burrs or other defects.

Use a suitable temperature measuring device with the appropriate range and a maximum error limit of ± 1 °C. Temperature measuring instruments must be calibrated at the immersion depth specific to the instrument used and within a temperature range that includes the Vicat softening temperatures to be measured. The temperature sensitive part of the instrument should be positioned no more than 20 mm from the point where the notch tip contacts the sample. The temperature sensing part of the instrument must not touch the sample or come into contact with any part of the frame.

Among the services provided by our organization within the framework of material testing services, there are also ISO 306 standard tests. Do not hesitate to contact our laboratory EUROLAB for your testing and certification requests.

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