Reliable testing is indispensable, especially for products that are designed for a particularly long service life. Plastics have already played a major role for years in construction products such as pipes, landfill sealing or geotextiles. These are applications with a long service life, high stress and a cost-intensive repair effort, which also pose a risk in the event of failure. Therefore, reliable testing of resistance is necessary for such products.
Further development of the SHT method also for polypropylene
With the Strain Hardening Test (SHT), a method for the rapid characterisation of stress crack resistance is available at the SKZ. In a research project, the method has now also been further developed for use with polypropylene, starting with polyethylene. By comparing the results of two comparative methods (full-notch creep test and cracked round bar test), it was possible to show that the test method can be used with high accuracy and reproducibility.
With this project, the SKZ is helping to create a basis for evaluating the stress cracking resistance of products made of polypropylene. For this purpose, the influences of various parameters - such as molecular structure, morphology, colour and filler addition and processing - on the results of the SHT were specifically evaluated.
Time-saving alternative to conventional methods
"The Strain Hardening Test provides the industry with another and economically attractive tool to characterise stress crack resistance", explains Britta Gerets, scientist at SKZ. Particularly in terms of the time required, the method offers an interesting alternative to the established testing options for polypropylene.
