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HDT/Vicat Standard

Test methods
  • HDT
  • Vicat
Heat transfer
  • Via heat transfer fluid

Determination of heat deflection temperature (HDT)

The Vicat testing instrument consists of a bath with an option to mount measuring heads. A built-in thermostat controls the bath temperature. The thermostat ensures a constant increase of the temperature with the standardized gradient over the entire test sequence.
Not only Vicat but also HDT tests can be performed with the measuring heads by simple mechanical conversion. The measuring heads accept the specimen and measure the puncture by the Vicat needle during Vicat tests or deflection of specimens during HDT tests via the installed digital measuring transducer.
In this configuration the Vicat testing instrument can be operated as a manual testing instrument. This means that you have to record the values of the digital measuring transducer and the temperature sequence manually.
We recommend the PC expansion as an accessory. It includes an interface box, the current testXpert software and the respective communication leads. The PC expansion enables fully automatic evaluation of the test job, printout of a test report as well as operation of the Vicat testing instrument via a PC. Temperature and travel values are recorded and saved together with the test parameters.

Advantages & Features

Advantages & Features

Functions, elements and interfaces
Test procedure
Re-cooling the heat-transfer fluid


  • Optional external re-cooling device for faster attainment of starting temperature
  • Testing to ISO 306, ASTM D1525, ISO 75 and ASTM D648.


Determination of heat deflection temperature (HDT)

  • as per ISO 75, Parts 1 to 3, and ASTM D648, Methods A and B, on thermoplastics, hard rubber and fiber-reinforced and filled thermosets.

Determination of Vicat softening temperature (VST)

  • of thermoplastics as per ISO 306 and ASTM D1525 .

Determination of creep behavior

  • under flexural load

Functions, elements and interfaces

  • built-in microprocessor-controlled electronics for temperature control and measured-value acquisition
  • measured values clearly displayed
  • safety thermostat
  • electronic level-monitoring
  • test control and data acquisition via PC with ZwickRoell Prüfsoftware (2 RS232 interfaces required in PC; 1x for temperature channel, 1x for displacement channel)
  • integrated compensation for heat expansion of measuring stations with PC operation
  • manual lowering of measuring stations
  • manual application of test weights.

Test procedure

As soon as the heat-transfer fluid has reached the starting temperature, the specimens are inserted into the measuring stations and lowered manually into the oil bath. In the next step the test weight specified in the standards is applied manually and the menu-driven test-sequence is started on the PC.

On completion of pre-heating under the influence of force, the displacement signals are zeroed (program-controlled) and the heating of the heat-transfer fluid at the pre-set rate is started. As soon as the required deflection, outer-fiber strain or penetration is attained, the heating is switched off and the test is ended.

Re-cooling of the heat-transfer fluid is started manually or by the PC via a solenoid valve. Specimens can afterwards be removed.

Re-cooling the heat-transfer fluid

Instrument cooling is via a cooling coil located in the oil-bath. Coolant (water) can be pumped in via a connection located on the left-hand side of the instrument.

Water-cooling is switched on manually, but not before 130°C at the earliest. For faster re-cooling a connection for an external re-cooling unit is available.

Technical Overview

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Learn more about HDT & Vicat

Determination of HDT VST plastics
ISO 306, ASTM D1525, ISO 75, ASTM D648
Determination of heat deflection temperature (HDT) and Vicat softening temperature (VST)
to Determination of HDT VST plastics
HDT and Vicat Testing Instruments
Standard-compliant testing to ISO 75, ISO 306, ASTM D1215 and ASTM D648.
The thermal resistance of plastics in many ranges of application is measured via heat deflection temperature (ISO 75 and ISO 306).
to HDT and Vicat Testing Instruments


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  • Product information: HDT/Vicat Standard PDF 798 KB

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