An Innovative Route to Circular Rigid Plastics

Abstract

An innovative route for plastics recycling is proposed, based on a combination of a logarithmic sorting process and colour plus high-resolution near-infrared (NIR) sensors. Although counterintuitive, it is shown that such a technology could sort clean flakes from rigid packaging waste into a very large number of different plastic grades with modest sorter capacity, provided that the chosen sensor is able to differentiate correctly between any two grades of plastics in the waste. Tests with high-resolution NIR on single pixels of transparent flakes from different types and brands of packaging show that this is indeed the case for a selection of 20 different packaging items bought from shops. Moreover, the results seem to indicate, in line with previous research, that high-resolution NIR data can be linked to important physical plastic properties like the melt flow viscosity and tensile strength. The attraction of deep sorting of waste plastics with relatively cheap sensors and modest sorter capacity is that the present industrial practice of tuning plastic grades to specific applications could coexist with commercial high-grade recycling at high levels of circularity and low carbon footprint. Therefore, advanced recycling technology is likely to be a societal alternative to phasing out plastics for rigid applications.

The impact of impurities on the mechanical properties of recycled polyethylene

“…Another alternative strategy is co‐collect the bottles with LWP, sort it conventionally, mechanically recycle the PE conventionally and to use advanced sorting technologies on the flake level, such as logarithmic sorting, 39 to obtain a single grade of rPE. This approach will also benefit from the same design‐for‐recycling guidelines.…”

A first assessment of the impact ofimpurities in PP and PE recycled plastics

“…To produce a range of high-performance recycled plastics suitable for circular applications such as packages and related consumer articles, advanced sorting technologies are required. To sort recycled plastics not only on the main type of polymer, but also on the grade, either advanced optical sorting technologies are required [Engelshoven van et al, 2019] or the packages need to be marked [Polymark, Prism, Holy Grail, Bezati et al 2011] and technologies have to be available for their sorting. Both approaches can result in recycled plastics that are sorted both on the main type and the grade of polymers.…”

Review on the photonic techniques suitable for automatic monitoring of the composition of multi-materials wastes in view of their posterior recycling

“…Different photonic technologies among those previously described play a substantial role in advanced polymer recycling ( van Engelshoven et al, 2019 ) but applications differ in terms of target characteristic, sorting strategy and position in the value chain.…”

“…In line with the different circular economy initiatives around the world, there is an increasing pressure for improving the plastic end-of-life (EoL) phase, especially towards increasing recycling and reducing depletion of our resources as well as leakage in land or marine environments. Since pure plastic fractions are generally needed to perform most recycling processes which are currently available at a commercial scale, more and more innovations are emerging in the field of plastic sorting ( Nüßler et al, 2016 ; van Engelshoven et al, 2019 ). Currently, such sorting is often performed automatically by coupling different identification and separation technologies based on size and density, as well as optical and magnetic properties (to remove ferrous packaging) with manipulation carried out via air jets, magnetic separators or mechanical pistons ( Neidel and Jakobsen, 2013 ).…”