Recycled PP strength to be assessed

SKZ Plastics Center is launching a two-year research project to develop an easy-to-use method for polypropylene (PP) recyclates.

PP recyclates are increasingly important in long-lasting applications such as furniture, packaging, automotive parts, textiles and medical devices. Mechanical recycling is the primary process for secondary PP.

The material is heated to soften or melt it and then mechanically formed into new products. Heating degrades the carbon backbone, however.

To ensure the reliability of the recyclates, the SKZ Plastics Center is working on a new testing method based on the Strain Hardening Test (SHT). Compared to other tests, SHT offers benefits such as easy implementation with standard testing technology (tensile test) and short testing times.

Slow cracks

A quantitative assessment of material quality is seen as crucial for the use of polypropylene recyclates. In particular, the failure mechanisms relevant to polyolefins must be considered, above all, a material’s ability to resist slow crack growth.

A strain hardening test (ISO 18488) is already established for virgin polyethylene in pipe applications.’
Initially, recyclates will be simulated by mixtures of materials with known properties. ‘Our main focus is on the dependence of the test results on mixture proportions and ratios,’ explains Britta Gerets, senior engineer at SKZ.

Virgin additives

The method will then be validated on post-industrial and post-consumer recyclates. In addition, the extent to which stress crack resistance can be improved by the targeted addition of virgin material will be investigated.
Interested parties can contact the research team via the project page.

More details available here >>

SKZ is a climate protection company and a member of the Zuse Association. This is an association of independent, industry-related research institutions that pursue the goal of improving the performance and competitiveness of industry, especially SMEs, through innovation and networking.