HDT and Vicat Testing

The Challenge

Using lightweight materials such as thermoplastic polymers can help to meet increasing demand for reducing vehicle weight, fuel consumption, and production cost. Automotive interior design is influenced by the proportions, shape, placement, and surfaces for the instrument panel, seats, interior trims, fans and shrouds, etc. Smoothness, feel, and stiffness are just a few of the material characteristics considered when developing automotive interiors. 

It is also important to evaluate short-term heat resistance. For example, the dashboard of your car on a hot summer day when the temperatures inside the car could reach up to 50°C (122°F). If the material used to make the dashboard is not tested under these conditions, the dashboard can potentially deform and be damaged. 

Our Solution

Instron's HV system allows performing both heat deflection temperature (HDT) and Vicat softening temperature (VST) tests according to both ASTM and ISO standards. The polymer specimen is immersed in a fluid bath where the temperature is raised uniformly at a specific rate (120°C/h or 50°C/h). A predefined load or stress is applied to the specimen in order to measure the temperature at which it shows a set deflection (HDT test) or penetration (VST test). Higher HDT and VST values obtained in a test signify that the tested material is suitable for high-temperature applications, making it a preferable material for automotive applications. In addition to the bulk properties, HDT and VST test results also provide input on the surface properties of a polymer. At temperatures higher than those established by an HDT or VST test, it can be anticipated that the polymer sample undergoes permanent deformation generating further surface defects.