In situ dissolved polypropylene prediction by Raman and ATR-IR spectroscopy for its recycling

Monitoring the dissolution of polyolefins using online spectroscopy analysis is addressed in this work, with the aim of optimizing plastic recycling processes. Two in situ spectroscopic methods are used to predict the dissolved polymer content: Raman spectroscopy and attenuated total reflectance infrared spectroscopy. Commercially available polypropylenes are considered. Different solvents are selected based on their affinity with polypropylene. Partial least squares regression is employed to identify models predicting the polymer concentration for each solvent from the online spectra. Raman spectroscopy was found to give a better prediction. It was therefore used to study different parameters influencing the dissolution process, such as solvent type, temperature and polymer form.