CD Laboratory for Impact of recycled materials on the mechanical lifetime estimation of polymers

This CD Laboratory researches the interactions between the design of plastic pipes, their loading con-ditions and the materials used. On this basis, methods for estimating the service life of such pipe systems are developed in order to contribute to their reliable and safe operation.

As polymer pipes are very frequently used in modern infrastructure, for example to transport gas or drinking water and wastewater, the use of recycled materials for their production represents an im-portant step towards sustainability. However, a major challenge is to use the available recycled poly-mers, which naturally vary in quality, to produce pipes that are as reliable and safe to operate as those made from less sustainable materials: Different molecular weight distributions, polymer inclu-sions and general impurities have a strong influence on the mechanical properties of the end product.

In the area of polypropylene, which has been comparatively little researched in this respect and is the focus of the CD Laboratory, there are even additional challenges: In the course of recycling, it is not possible to separate different types of polypropylene, and the different crystal formation depending on the mixing ratio has a potentially strong influence on the final properties. This can lead to highly un-predictable results when using currently available methods. And while modern polymer pipe systems are expected to function reliably for at least 50 years, knowledge of the relevant damage and failure mechanisms under long-term static loading and their determination is still very limited, especially for polypropylene pipes.

The CD Laboratory team is therefore working towards closing this knowledge gap in materials science by focusing on three main topics: Firstly, analysing in detail the underlying mechanisms responsible for the long-term properties of polypropylene. Secondly, how the morphology of a "polypropylene mix-ture" develops in relation to its components (the individual polypropylene materials) and how this af-fects the mechanical properties of the end product. And thirdly, even more precise methods for esti-mating the service life of polypropylene pipes are to be developed on the basis of these findings.

The CD Laboratory will provide important information on the basis of which the industry can find ways to deal with the constantly changing material quality of recycled materials and ensure the safe opera-tion of their products: this will enable an even better, durable and sustainable infrastructure for future generations.