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Virgin-like recycled polypropylene from waste carpets

Tue, 30 August, 2022

Recovering pure plastics from post-consumer waste was considered necessary early on in order to save resources and meanwhile is also seen as a potentially lucrative business idea in times of rising crude oil prices. Interest in new and increasingly efficient processes is growing steadily. First technologies were based on purely mechanical recycling. Shredded plastic waste is separated by purely mechanical processes. However, the result is not pure resin, since dyes and additives cannot be extracted from the complex matrix. This is now being referred to as “down-cycling” of plastics.

"Reactive recycling" processes are in turn based on a different approach: Pyrolytic processes break plastic molecules into their individual liquid or gaseous components. While this approach succeeds in returning to the raw materials, it is a complex multi-step process that requires high energy input. Small profit margins thus limit its applicability.

ISOPREP pursues a completely different strategy: the use of a non-toxic, low vapor pressure ionic liquid tuned to dissolve only polypropylene. While the separation of impurities is thus greatly facilitated, the complete recovery of the ionic liquid is a challenge. The Institute of Process and Particle Engineering, part of the Graz University of Technology, has developed approaches to overcome this problem with its know-how in the field of solid-liquid separation.