Consider two scenarios; the lid of a plastic container should still fit correctly after coming out of the dishwasher, plastic piping intended for transporting hot liquids should not warp. In both of these examples, the designer needs precise data which is used to assess the risk of material deformation or to set the limits for manufacturing. At this year’s International Forum for Materials Testing in Ulm, Germany, Zwick is introducing a new and complete line of products for making these measurements.
The tests for the heat deflection temperature (HDT) and the Vicat softening temperature (VST) form part of the fundamental characterization methods for plastics, and are described in ISO 10350-1.
Thermoplastic plastic materials do not exhibit an exact melting point marking the transition from a solid to liquid, so the Vicat softening temperature was introduced as a substitute for the melting point for measurement and test purposes. It defines the temperature at which a thermoplastic material begins to soften.
The heat deflection temperature is an additional measurement parameter. A prismatic test specimen is flexed and then heated with a defined increase in temperature. The heat deflection temperature is reached when the specimen reaches a flexure value defined in the Standards. Since this temperature result is dependent on the applied load, specimen geometry, heating rate, and the chosen flexure value, the HDT is a value which allows different materials to be compared with one another.
Zwick’s new product line includes manually operated “HDT/Vicat Standard” models with computerized calculations from the measured data. The “HDT/Vicat Allround” models additionally have computer controlled functions such as motorized lowering of the measuring stations, and the motor-driven application of test weights. Both models are available in different variants with one to six measuring stations.
While the specimens in the Standard and Allround models are heated in a bath with a heat transfer liquid, the “Vicat D” model applies the dry process where the specimen is heated in a copper block as described in DIN EN ISO 306. This method features many advantages for the operator such as no annoying vapor, the test is very clean, and tests at higher temperatures are no longer a problem. The test is fully software controlled and requires no intervention by the operator.
The new product line now enables Zwick to offer a total testing solution for Vicat and HDT testing, and all of the Standard, Allround, and Vicat D models are conveniently operated using Zwick’s testXpert® II testing software. This standardized operation is a significant advantage for operators who already use other Zwick products. In addition, the software also contains many other useful functions for measurement and control graphs, result calculations, and data storage.
With its new product line, Zwick is targeting raw material manufacturers, compounders, recyclers, research and development and technical support, as well as final product manufacturers, plastic pipe manufacturers, automobile and aerospace industry, universities and institutes, and test service providers.