Quality assurance of polyethylene blends and recyclates
The increasing use of recycled materials in industry makes the further development of existing test methods an urgent necessity. At the SKZ Plastics Center, a team of experts is therefore researching the development of a rapid test method to quantify the stress crack resistance and has achieved significant results.
PE recyclate as granulate, extruded film, pressed sheet and test specimen after the strain hardening test (SHT). (Photo: Britta Gerets, SKZ)
SKZ develops test method for evaluating recyclate quality
Blends and recyclates are increasingly being used in industrial practice. In view of the development towards a circular economy, this is an encouraging trend. However, the use of recyclates in particular is often limited to applications with very low material requirements. Tests are the basis for ensuring high quality of materials and products. For many years, a wide range of test methods have been established and proven in practice for plastics.
Rapid quantification of stress crack resistance
Many manufacturers are still reluctant to use recycled materials more widely in demanding applications. The basic prerequisite for this to change is the further development of the test methods that have been developed for virgin materials. At SKZ, researchers have taken on these tasks and developed a method for the rapid quantification of the stress crack resistance of blends and recyclates made of polyethylene based on the strain hardening test (SHT). “The aim was to develop a procedure for the production, testing and evaluation of test specimens that takes into account the challenges associated with blends and recyclates. In particular, the influence of blend components and ratios had to be investigated,” explains Britta Gerets, Senior Engineer at SKZ.
Direct application possibilities for industry
In the project, the institute's experts were also able to successfully demonstrate a change in the stress crack resistance of recyclates by adding virgin material. This can thus be used specifically to optimize properties. The findings obtained at SKZ offer direct application possibilities for industry. SHT is a quantitative method for testing the quality of materials. “Thanks to the findings, SMEs can also very quickly and easily characterize their products and assess whether material requirements are met, even when recyclate is added,” says Ruben Schlutter, group leader for component properties at SKZ.
More about the SKZ research group Component Properties
