# Deinking of Post-Consumer Waste Flakes—Objective Assessment of Ink Removal on Inhomogeneous Film Fractions

## TL;DR

This paper introduces a new method to objectively assess ink removal from plastic waste flakes, improving the quality of recycled plastics.

## Contribution

A novel image-based method for evaluating deinking efficiency on inhomogeneous plastic flakes is proposed.

## Key findings

- An image-based analysis using grey scale and statistical metrics assesses deinking efficiency.
- The method is compared to the CIE Lab-method and its robustness is evaluated.
- The approach identifies effective parameters for ink removal on inhomogeneous flakes.

## Abstract

The deinking of plastic packaging waste offers the potential of decreasing contamination and thus increasing the overall quality of recycled plastics, enabling their use in more demanding applications. However, for flexible polyethylene packaging waste, deinking is not yet implemented on an industrial scale and there is currently no objective methodology to evaluate the deinking effect on those inhomogeneous flakes. In this study, a novel approach for the objective assessment of ink removal on flexible post-consumer waste (PCW) is proposed. Via an image-based analysis, the transparency of the flakes is transformed into the 8-bit grey scale, and the deinking efficiency of several experiments is compared via the skewness and median of grey value distributions. The method is compared to the International Commission on Illumination (CIE) Lab-method and its robustness against wrinkles and overlaps is critically discussed. Using this analysis method enables the investigation of the general behaviour of contaminated PCW materials in deinking and identifies the most effective parameters for ink removal on inhomogeneous flakes.