In order to achieve the European recycling targets, the Austrian recycling rate for plastic packaging must improve in the next few years. Packaging films used for food protection or transport purposes are hardly recycled.

Multilayer packaging films are particularly critical because they represent contamination within the mono-material streams and currently cannot be detected by modern sorting equipment. The problem is that these devices can only detect the surface layer facing the detector and cannot identify the different materials that are underneath the surface layer. The Multilayer Detection project aimed to improve the identification and sorting of multilayer packaging films by modifying the commonly used NIR-based sorting devices. By applying the concept of transflectance, good detection and separation of multilayer packaging materials from mono-material streams could be achieved. The adaptation consisted of placing a reflective background on the sorter to (I) increase the intensity of the signal reflected back to the sensor and (II) obtain information about the materials beneath the surface. Polymer fractions sorted in this way resulted in recyclates with better properties and processability. In addition, the LCA results showed that the optimized sorting process can reduce CO2 emissions and enable a closed recycling loop.

This work was funded by the province of Styria and Zukunftsfonds Steiermark for the project “Multilayer Detection” (project number 1314).