Extrusion International 5-2024

15 Extrusion International 5/2024 In-line Quality Control for Plastic Recyclate  The RecyQuant research project makes it possible to monitor and maintain tolerable levels of foreign materi - als in the recyclate directly in the process. The joint proj- ect between ColVisTec AG and the SKZ Plastics Center successfully implemented the detection of foreign poly - mers and the direct readjustment of the dosing scales. The basis for this was the modeling of the photometric data of the plastic melt. A major challenge when using recyclates in the ex - truder process is the fluctuations in quality. In addition to general impurities, post-consumer recyclates in par - ticular contain foreign polymers. However, excessive levels of foreign polymers in the base polymer lead to inferior product quality. In a joint project, the SKZ Plastics Center and ColVisTec took on the challenge of measuring and automatically correcting the foreign polymer content during the ongoing process in 2022. In the event of a deviation from defined tolerance ranges, the process sequences were to be automatically adjusted by cou- pling with the extruder's system technology. The aim of the two-year research project was to realize a new application of CVT technology, which is to be market - ed as a system combining hardware and software. The research team was very satisfied with the results once all the tests had been completed. The main objec- tives were achieved and the concept was proven on a demonstrator. First of all, a chemometric model for pre - dicting the foreign polymer content (polyethylene con - tent between 0 and 10% by weight) in the base polymer (polypropylene) for virgin and recycled material was cre - ated in the project. A reduced wavelength range in the near-infrared could be determined for a high prediction accuracy. The suitability of the photometric approach was demonstrated using a spectrometer and modeling. In addition, both a cost-effective broadband probe for the UV-VIS-NIR spectral range and a flexible software package for control were developed. The latter enables the dosing scale to be controlled when the threshold val - ue of the foreign polymer quantity is exceeded. “The decisive factor is that carrying out tests using demonstrators on realistically colored recycled material was able to prove that the measuring system is suffi - ciently sensitive even for weakly reflective material,” ex - plains Cosima Güttler, Scientist Spectroscopy at SKZ. The solution developed enables significantly improved qual - ity control when using recycled material and therefore makes a valuable contribution to both product quality and the circular economy. SKZ Plastics Center Cosima Güttler, c.guettler@skz.de www.skz.de Test setup at the SKZ (Photo: Kilian Dietl, SKZ) Herbold Meckesheim GmbH Industriestrasse 33 I D-74909 Meckesheim I Tel: +49 6226 932-0 I herbold@herbold.com I www.herbold.com Energy Efficient ▪ Easy Maintenance ▪ Excellent Flakes Modular system solutions for automated PET washing lines