ISO 306, ASTM D1525, ISO 75, ASTM D648: heat deformation temperature (HDT) and vicat softening temperature (VST)
ISO 306, ASTM D1525, ISO 75 and ASTM D648 standard describes the heat deformation temperature (HDT) and vicat softening temperature (VST) determination.Thermal deformation temperature and vicat softening temperature is under the condition of similar characterization of plastic highest use temperature property values.
Especially thermoplastics, under the high temperature will gradually lost its rigidity and hardness.The performance based on the sample measurement by applying a constant load, with the increase of temperature, deformation of specimen will gradually, embodied in deflection (HDT) or needles indentation (VST).
Plastic manualThe VST vicat softening temperatureThe thermal deformation temperature of HDTTest requirementsHeat transfer methodThe test system
The vicat softening temperature, VST ISO 306 and ASTM D1525
The vicat softening temperature (VST), pressure needle will load weight, hardness loss through pressure needle under the condition of temperature rising of indentation is measured.VST is refers to the pressure needle to specify the temperature at which the indentation depth.The method is used for characterization of molding material, it isISO 10350-1Part of the standard stipulated in the single point data.Because the sample size is relatively small, this method can also be applied to measuring intercept down the sample from the parts.
Heat deformation temperature (HDT), ISO 75 and ASTM D648
For the thermal deformation temperature (HDT), three point bending method is used to measure the stiffness loss.This method is usually used for characterization of molding material, it isISO 10350-1Standard stipulated in the part of a single point of data, usually displayed on the material card (please refer towww.campusplastics.com).ISO 75-1, ISO 75-2, ISO 75-3andASTM D648Standard in this test method was introduced in detail.
Test requirements
According to the measured frequency and time used in heat transfer fluid subcooling, can use different versions of the instrument.Range from relatively simple manual operation instrument to support most of the automatic test sequence of instruments.The quality of较高的仪器配有电气互锁保护盖和集成式排烟选装件，可为操作员提供额外的便利性和安全性。
Test starts at ambient temperature.ISO 75-1The highest standard starting temperature of 27 ° C.After applying appropriate standards specified in the test weight, material began to deformation of the changing over time.This part of the deformation is not needed, 5 minutes later, the pressure needle through the deflection measurement of displacement or indentation to zero can be minimized.After testing to 50 K or 120 K/h/h of heating rate on the heat transfer fluid heated, until reach the standard based on deflection or indentation depth.The temperature that is representative of the test results.
Heat transfer method
- Because of the heat is passed a set good heating rate, in this test method is passed to the sample quantity of heat is very important.
- Classic methods using a heat transfer fluid, usually silicone oil.Through the sample and good contact with heat conduction medium can get a high comparability of test results.
- In addition, over the years has also set up a variety of options in the standard methods of heat transfer.One of the alternative method has been in the Vicat D model technology.In this method, the sample by the two heating heating disc contact heat transfer.This method does not need to use silicone oil.
