Headspace and extraction gas chromatography of plastic waste during different reprocessing steps of mechanical recycling

Description

Mechanical recycling is one of the most important strategies for plastics recycling. It involves pretreatment (sorting and shredding) and subsequent reprocessing steps such as cold/hot washing, and the application of various decontamination technologies. Combining these reprocessing steps should lead to an increased cleaning effect and recyclate of higher quality. The effectiveness of the single steps is often not known. For this project, plastics waste with a high content of food contact material was hand sorted, separated into polypropylene (PP) and polystyrene (PS), and further divided with respect to color allowing individual examination all along the recycling path. The fractions (different materials, different colors) were reprocessed in three subsequent steps namely hot washing, pelletizing and a final solid state decontamination. Two separate gas chromatography - mass spectrometry (GC-MS) methods were established for analysis. Static headspace sampling allowed a direct analysis of the more volatile substances whereas GC-MS analysis of extracts was used for covering the less volatile compounds. Combining the results from these two approaches proved extremely valuable for conclusively discussing the effectivity of the washing process during mechanical recycling. A direct comparison for PP and PS showed different polymer degradation behaviors during reprocessing as well as different kinds of contaminations. Thereby PP and PS could be distinguished based on their different fields of application. In a similar way also for the different color fractions, variations in the degree of contamination were observed. PP was mainly cleaned during primal washing while further reprocessing had little to no impact. Contrary, sufficient cleaning of PS was only possible by subsequent pelletizing and solid state decontamination.

Period	24 Sept 2024
Event title	Chemietage 2024
Event type	Conference
Location	AustriaShow on map