Due to recent changes in the EU regulations, improvements in the useability of recycled plastics are required. However the lack of intuitive solutions make it difficult and intransparent to comply with these regulations.

While the increased use of recycled materials is a crucial step towards a circular economy, integrating them into plastics production processes presents significant challenges.

The inherent variability of recycled materials – especially considering the increasing use of post-consumer recyclates (PCR) – often leads to uncertainty about final part quality. Damaged materials and inconsistent quality levels from batch to batch, bag to bag or even within a tank filling can cause significant deviations in molding behavior compared to virgin polymer compounds. To give an example: The molecular chain length distribution of a plastic depends largely on the history and processing parameters of the plastic but has a direct influence on the flowability of the material. This inconsistency can lead to process inefficiencies, higher scrap rates, and difficulties in achieving desired product performance and should therefore be taken into account in the process control.

Furthermore, detecting deviations during the molding process becomes even more complex with recycled materials, as control is primarily limited to the stages of material pre-processing, injection, and post-process quality assurance (QA) testing. The lack of ‘live’ feedback and material monitoring within the mold hinders the ability to identify and address issues promptly.

Until now, the possibilities for gaining insight into material behavior were limited. Material suppliers are working diligently to enhance the quality of recycled content through meticulous sorting and cleaning processes. While this approach has yielded promising results thus far, the increasing demand for recycled materials is likely to render it difficult to maintain consistent high quality without taking any further measures.

Machine manufacturers are also actively developing technologies to improve the processing of recycled materials. Many of these solutions focus on controlling material volume and machine pressure to ensure consistent injection into the mold. However, once the material enters the mold cavity, monitoring and control becomes significantly more complex. Cavity pressure sensors offer some insights, but their effectiveness is limited to the early stages of the molding process, as they become less sensitive once the initial plastic layer solidifies (frozen skin).