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Fluorescence filters hold promise for plastics recycling

Fluorescence filters could make recycling plastics of different types substantially easier in the years to come.

According to scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich, the solution to sorting plastics faster and more easily for recycling could be to expose them to a brief flash of light.

When this is done, the plastic fluoresces, and by observing the decay of this fluorescence it is possible to identify the polymers contained within the material.

This means that a relatively simple setup of fluorescence filters could be all that is needed to easily identify different types of plastic from a typically mixed selection of recyclable materials.

Separating different types of plastic can be crucial to making sure the recycled material is usable, and the scientists say contamination of less than 5% by a different type of material can have an adverse impact on the chemical properties of the plastic.

Professor Heinz Langhals of the LMU Department of Chemistry says: “Polymers represent an interesting basis for the sustainable cycling of technological materials. The crucial requirement is that the recycled material should be chemically pure.

“In that case, bottles made of PET, for example, can be relatively easily turned into synthetic fibre.”