Background Information


i. Deflection Temperature Under Load (DTUL) – a specified bending stress is applied by means of a presser to the sample immersed in oil tank and temperature of the heating medium (oil) is raised at constant rate and the temperature when the sample attains specified deflection is determined as the deflection temperature under load (DTUL). There are flatwise testing method and edgewise testing method according to the direction of bending of sample. After conducting test, the heating medium is safely cooled at fast rate by means of an externally installed heat exchanger and repeated tests are automatically continued.
ii. Vicat Softening Temperature (Vicat) – manually or automatically changing the presser with a needle shaped presser and measuring the temperature at which the needle penetrates 1mm into the sample. This test method is not recommended for ethyl cellulose, non-rigid poly(vinyl chloride), poly(vinylidene chloride), or other materials having a wide Vicat softening range.
iii. Ball Pressure Temperature – by manual operation it can conduct ball pressure test specified as heat resistance test for electric products by changing the presser, etc.


This machine evaluates thermal properties of plastics according to the following standards.

  1. Deflection Temperature Under Load (DTUL) testing method JIS K 7191-1, 2 (ISO 75-1, 2)
  2. Vicat Softening Temperature (VST) testing method JIS K 7206 (ISO 306)
  3. Ball Pressure Temperature testing method (IEC, 335-1)
  4. ASTM D648 – Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position
  5. ASTM D1525 – Standard Test Method for Vicat Softening Temperature of Plastics

Test Summary

1. Heat deflection temperature to ISO 75 (HDT)

Heat deflection temperature (HDT) (ISO 75 -1/2/3) indicates the relative behavior of different types of material under load at elevated temperatures. It is determined for materials such as thermoplastics, hard rubber and duroplastic laminates.

Test sequence

  • A specimen is placed in a 3-point flexure test kit and loaded with the test weight required to achieve the flexural stress specified in the standard.
  • The temperature of the oil-bath is then increased at a uniform heating rate of 120K/h.
  • The temperature at which the specimen reaches the deflection specified in the standard is determined.


2. Vicat softening temperature (VST) to ISO 306

Vicat softening temperature (VST) provides a value for the temperature at which a thermoplastic material begins to soften rapidly. This temperature is determined using a needle-shaped indenter with a round cross-sectional area of 1 mm².

Test sequence

  • The indenter is placed on the plastic specimen and loaded with a defined test weight.
  • The specimen is then heated at a specified rate.
  • The VST is obtained when the needle penetrates to a depth of 1 mm.
  • ISO 306 and ASTM D1525 are identical with regard to the test sequence.

ISO 306 distinguishes between 2 procedures and 2 different heating rates, giving 4 different test methods in all:

  1. Method A = 10 N load, heating rate 50 K/h
  2. Method A = 10 N load, heating rate 120 K/h
  3. Method B = 50 N load, heating rate 50 K/h (preferred method for comparative tests ISO 13050-1)
  4. Method B = 50 N load, heating rate 120 K/h

Test Materials

Ethylene vinyl acetate, polystyrene, high-density polyethylene, nylon, polypropylene, ABS, acrylic, polycarbonate, PMMA, polysulfone, acetal copolymers, etc.

Vicat Softening Temperature test only applicable to Thermoplastic material.

What should the users look for in getting an HDT Vicat Test Machine

  1. Hassle-free – The independent specimen base can be pulled out when attaching the test samples to the specimen base. This enables the high workability for the operator and also prevents test sample from falling into the oil bath.
  2. Ease Operation – The specimen bases will automatically go down into the oil bath when the operator starts the test through software. After the test has been conducted, the machine will automatically cool down the oil bath and specimens before the specimen bases rise automatically at the completion of the test.
  3. Better Heating Rate Accuracy – Able to meet and achieve better heating rate accuracy.
  4. Fast Cooling – The Double Cooling Type (Cooling Water + Refrigerator) which allow high throughput of analysis
  5. Space Saving – Incorporation of refrigerator into machine internal design allows space savings
  6. Safe operation – by design of emergency stop, safety door (option), over-heat dial, oil bath net, etc.


Yasuda HDT Vicat Tester

                                                     Yasuda HDT Vicat Tester