Vicat Softening Temperature
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Vicat softening temperature
Methodological basics
The aim of the VICAT heat resistance method is to quantitatively characterise the heat distortion resistance temperature of a plastic. For this purpose, the VICAT heat distortion resistance temperature is determined, which, for methodological reasons, does not have to be quantitatively identical to the heat distortion temperatures determined by other experimental methods (such as the heat distortion temperature HDT) [1].
The ISO 306 standard [2] specifies four methods for determining the VICAT softening temperature, designated according to the selected test load and heating rate:
Procedure
- A 50: with a force of 10 N and a heating rate of 50 °C/h
- A 120: with a force of 10 N and a heating rate of 120 °C/h
- B 50: with a force of 50 N and a heating rate of 50 °C/h
- B 120: with a force of 50 N and a heating rate of 120 °C/h
The temperature in °C at which an indenter tip penetrates 1 mm deep into the surface of the test specimen is determined. The indenter tip has a circular cross-section surface with an area of 1 mm2 . The measured temperature is referred to as the Vicat Softening Temperature VST. Square (base area 10 mm x 10 mm) or round (minimum diameter 10 mm) test specimens with a thickness of 3 mm to 6.5 mm are used for the test. The surfaces must be flat and parallel, as well as burr-free.
Principle of the VICAT test equipment
The VICAT test device consists of a rod with a support plate for the test weights and a fixture for the indenter tip, as well as a calibrated dial gauge for determining the indentation depth. The test specimens described are positioned on a test specimen support and heated at a defined heating rate in a silicone bath or with air heating (see Figure 1).
| Fig. 1: | Test setup for determination VICAT softening temperature |
Examples of VICAT softening temperatures
Since the VICAT softening temperature responds to a change in molecular size, the measurement can be used to infer processing-related thermal damage.
| Material | VST (°C) | |
|---|---|---|
| A 50 | B 50 | |
| unreinforced plastics | ||
| PE-HD | 75 | |
| PE-LD | 52 | |
| PE-UHMW | 130 | 74 |
| PP | 150 | 90 |
| POM | 150 | |
| PA 6 | 200 | |
| PBT | 190 | |
| PC | 145 | |
| PMMA | 103 | |
| PVC-U | 83 | 77 |
| PVC-P | 42 | |
| PS | 84 | |
| SAN | 106 | |
| ABS | 87 | |
| reinforced plastics | ||
| PP + 20 M.-% Talkum | 153 | 95 |
| PP + 40 M.-% Talkum | 153 | 98 |
A comprehensive literature review on the experimental values of Vicat softening temperatures is presented in [5] for ABS, ASA, ECTFE, ETFE, EVA, FEP, HABS, PA6, PA66, PA46, PA610, PA612, PA 11, PA 12, PA1010, PA1, PB-1, PPI, PBT, PC, PCTFE, PE-HD, PE-HMW, PE-LD, PE-UD, PE-MD, PE-UHMW, PE-X, PEEK, PEI, PEK, PESU, PET, PHR, PI, PMMA, PMMI, POM, PP, PPA, PPE, PPS, PPSU, PS, PSU, PTFE, PVC, PVDF, SAN and SB-Copolymers are included. In addition, examples of the dependence of the Vicat softening temperature on filler contents of particles or nanoparticles in various thermoplastics are given.
See also
References
| [1] | Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser Munich (2022) 3rd Edition (2022) pp. 570–573 (ISBN 978-1-56990-806-8; see AMK-Library under A 22) |
| [2] | ISO 306 (2022-11): Plastics – Thermoplastic Materials – Determination of Vicat Softening Temperature (VST) |
| [3] | Carlowitz, B.: Tabellarische Übersicht über die Prüfung von Kunststoffen. Giesel Verlag für Publizität, Isernhagen (1992) (ISBN 978-3980294201; see AMK-Library under C 9) |
| [4] | Campus® Database: http://www.campusplastics.com (access at 02.05.2025) |
| [5] | Kotter, I., Grellmann, W.: Vicat Softening Temperature and Heat Distortion Temperature. In: Grellmann, W., Seidler, S.: Mechanical and Thermomechanical Properties of Polymers. Landolt-Börnstein. Volume VIII/6A3, Springer Berlin (2014) pp. 62–75, (ISBN 978-3-642-55165-9; see AMK-Library under A 16) |
Compilation of Standards
- ASTM D 1525 (2025): Standard Test Method for Vicat Softening Temperature of Plastics
- ISO 2507 (1995-02): Thermoplastics Pipes and Fittings – Vicat Softening Temperature –
- Part 1: General Test Method
- Part 2: Test Conditions for Unplasticised Poly(vinyl Chloride) (PVC-U) or Chlorinated Poly(vinyl chloride) (PVC-C) Pipes and Fittings and for High Impact Resistance Poly(vinyl chloride) (PVC-HI) Pipes
- Part 3: Test Conditions for Acrylonitrile/butadiene/styrene (ABS) and Acrylonitrile/styrene/acrylic Ester (ASA) Pipes and Fittings