The properties of polymeric materials at constant load change with time. At constant stress, material deformation increases with time. The process of increasing the deformation with time at constant stress is called creep, while the material property, which results from this behavior, is called creep compliance.
Within the thesis, we composed a simple device for demonstrating the creep behavior of various polymer materials. The device allows measurements at constant temperature and various stress levels. Within the thesis, we measured five materials: two rubbers with different hardness, polyvinyl chloride (PVC), low density polyethylene (LDPE) and thermoplastic polyurethane (TPU). The tests were carried out on a time scale from 250 to 900 seconds. The properties of rubber with higher hardness and polyvinyl chloride were measured in the time range of 45000 seconds.
The results obtained with simple device were compared with the results obtained on a sophisticated commercial device. The comparison of the measurements has shown that the simple device can be used to estimate the time-dependent properties of polymeric materials; however, the measurements on this device underestimate the creep compliance on average by 20.2 %.
|
