The plastics department of the Materials Testing Institute (MPA) in Darmstadt carries out tests on plastics and elastomers according to national and international standards. Its business activities comprise durability analysis on plastic components including long-term internal pressure loading, long term behavior on electric insulating materials and the mechanic degradation on composites under static and cyclic loading.
An important activity is the determination of thermal properties (Vicat or HDT tests) according to ISO 306, EN 727 or ISO 75. During these tests, a plastic specimen in a silicone oil bath is mechanically loaded and then heated using a constant temperature gradient. At a specific deformation of the specimen the instantaneous temperature is recorded as the “Vicat softening temperature” or the “Heat deflection temperature”.
Dependant on the different test methods, it is necessary for Vicat or HDT testers to be configured in a very versatile way:
- For pre-conditioning with or without mechanical loading
- For the degree of mechanical loading during the test
- For the loading time in the non-heated bath
- For the temperature gradient
All these procedures require a well structured and unambiguous system to guide the operator – particularly if a Vicat / HDT-tester consists of several individual test stations. Even inexperienced operators will not have difficulty in using the instrument and the process capability can be maintained.