The effect of cross-contamination on the long-term crack resistance
of polyethylene and polypropylene
In order to create added value of plastics in terms of improved circular economy, an increasing use of recycled polymers becomes more and more important. For long-term applications, such as plastic pipes, the resistance against crack initiation and slow crack growth is a crucial material property as it is directly linked to the structural lifetime. The current paper demonstrates the characterization of the slow crack growth resistance with the cyclic cracked round bar (CRB) test and shows how recycled polyethylene (PE) and polypropylene (PP) perform. Moreover, systematical investigations of PE mixed with increasing amounts of PP will be presented as well as blending of different PE types, typically used for extrusion and blow moulding. The generated results confirm a significant impact of the purity and degree of sorting on lifetime relevant long-term properties.