Márton Bredács - Polymer Competence Center Leoben GmbH, Leoben, Austria

Jutta Geier - Polymer Competence Center Leoben GmbH, Leoben, Austria

Mario Messiha - Polymer Competence Center Leoben GmbH, Leoben, Austria

Gernot Oreski - Polymer Competence Center Leoben GmbH, Leoben, Austria

Raphael Horvath - IRsweep AG, Staefa, Switzerland

Szilveszter Gergely - University of Technology and Economics Budapest, Hungary

Gerald Koinig - University of Leoben, Leoben, Austria

Gerald Pinter - University of Leoben, Leoben, Austria

In 2020, 367 million tons of plastics were produced globally, whereof in Europe 20 % was used in the building & construction sector to manufacture in significant proportion polyethylene (PE) and polypropylene (PP) pipes [1]. To increase the current 30 % of recycling rate improving the quality of recyclates and consequently facilitate the production of recycled high-value products such as pipes is essential. Previous studies [2, 3], showed that improved mechanical sorting of post-consumed plastics would improve the quality of recyclates and pipes containing recycled PO grades.

State of the art near infrared (NIR) sensors of mechanical sorting lines limit the sorting degree due to the characteristics of the recorded overtone vibrations. Thus, the objectives of this work are to improve the current NIR sorting technology applying multivariate data analysis and to investigate the applicability of dual comb spectroscopy in the mid-IR spectral range as a new sensor technology in mechanical recycling. Applying principal component analysis (PCA) separation of virgin high-density PE and PP grades were found to be possible, hence higher degree of sorting could be achieved for post-consumed PO products with NIR sensors. In fact, PCA of post-consumed PO indicate that processing method (e.g.: extrusion, injection molding) based separation is possible. Moreover, PE density can be predicted accurately with partial least square regression relying on Raman and FTIR spectroscopy [3]. Although the current NIR spectra are not suitable for MFR and density prediction during the sorting process, an emerging new method applying dual comb spectroscopy provides high spectral resolution [4] and allows the accurate prediction of MFR and density of PE. An in-line, mid-IR spectroscopy based MFR and density prediction could lead to pure recycled fractions containing only PE pipe grades. Such enhancement would be a significant step towards increased plastic recycling and towards circular plastic pipe products.

Acknowledgement

This work was performed at the PCCL, within the framework of the COMET-program of the Federal Ministry for Transport, Innovation and Technology and Federal Ministry for Economy, Family and Youth with contributions by the IRsweep AG, Montanuniversitaet Leoben, BUTE.

Keywords

PO pipes, mechanical recycling, spectroscopy, PCA