Depth-Sensing Macroindentation Test and Stepped Isothermal Method-Accelerated Assessment of the Local Retardation Behaviour of Thermoplastic Polymers

摘要

The prototype of a depth-sensing macrohardness testing system with temperature chamber and temperature controlling unit for contact heating/ cooling was upgraded in terms of control and software in such a way, that it allows application of the Stepped Isothermal Method (SIM) as for now. The SIM is a single-specimen method, for which the temperature is raised stepwise at constant load and kept constant for a given time for each step, where the changes in indentation depth are measured as a function of time in this case. After correction of the thermally induced change in indentation depth and mathematical procedures a master curve construction is realised along a logarithmic time axis. The method was successfully applied to the assessment of the long-term creep behaviour of different thermoplastic polymers such as PP, PE-HD, PET and PVDF. The results obtained were compared with results of the SIM using tensile testing and the short-term creep test using the depth-sensing macrohardness testing system.