Fraunhofer-Gesellschaft Exploiting new material flows and developing new synthesis strategies
The optimizations in material recycling achieved in the project primarily focus on tapping into other material flows that were previously difficult or impossible to recycle. In order to enable high-quality applications for reuse, knowledge was gained on the ageing assessment of recyclates. Simulations for recycling cycles and the use phase were created and suitable test specimens for sensor technology were manufactured. These enabled in-depth analysis of the ageing process, for example with regard to molar mass degradation and build-up in polyamides, changes in melt viscosity or restabilization processes. The individual ageing effects were also correlated in order to be able to compare damage phenomena, for example.
An important result is the determination of tipping points for PP and PA, beyond which material recycling no longer makes sense and chemical recycling should be chosen instead. In order to efficiently determine changes in molecular weight that have a direct effect on viscosity, a method for online rheology was developed as a quick diagnostic tool for formulation development with the use of appropriate additives.
The samples produced from recyclates were tested with regard to their mechanical performance (tensile tests, notched bar impact tests), characterized microstructurally and compared with virgin material. In addition, the large-scale production of PA recyclate with high purity was carried out, which was obtained from shredder waste using solvent-based recycling. Blends obtained from recyclates in the project were compounded using twin-screw extruders (type ZE25A-UTX) for the production of demonstrators in injection molding.