Towards Distributed Recycling with Additive Manufacturing of PET Flake Feedstocks.

Helen A Little,Samantha L Snabes,Nagendra G Tanikella,Matthew J Reich,Joshua M Pearce,Matthew J Fiedler

doi:10.3390/ma13194273

Helen A Little, Samantha L Snabes + Show 4 more

Open Access

https://doi.org/10.3390/ma13194273

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Abstract

This study explores the potential to reach a circular economy for post-consumer Recycled Polyethylene Terephthalate (rPET) packaging and bottles by using it as a Distributed Recycling for Additive Manufacturing (DRAM) feedstock. Specifically, for the first time, rPET water bottle flake is processed using only an open source toolchain with Fused Particle Fabrication (FPF) or Fused Granular Fabrication (FGF) processing rather than first converting it to filament. In this study, first the impact of granulation, sifting, and heating (and their sequential combination) is quantified on the shape and size distribution of the rPET flakes. Then 3D printing tests were performed on the rPET flake with two different feed systems: an external feeder and feed tube augmented with a motorized auger screw, and an extruder-mounted hopper that enables direct 3D printing. Two Gigabot X machines were used, each with the different feed systems, and one without and the latter with extended part cooling. 3D print settings were optimized based on thermal characterization, and both systems were shown to 3D print rPET directly from shredded water bottles. Mechanical testing showed the importance of isolating rPET from moisture and that geometry was important for uniform extrusion. The mechanical strength of 3D-printed parts with FPF and inconsistent flow is lower than optimized fused filament, but adequate for a wide range of applications. Future work is needed to improve consistency and enable water bottles to be used as a widespread DRAM feedstock.

Highlights

The vast majority of plastics end up landfilled or contaminating the natural environment, as the global polymer recycling rate is an embarrassingly low 9% [1]
Part of the problem is that it is costly to separate the numerous types of plastic, and as consumers have no direct financial incentive to do it in conventional centralized recycling, increasingly sophisticated sorting technologies are proposed [7] to reach a circular economy [8,9,10]
Another approach to reach a circular economy for plastic is Distributed Recycling for Additive

Summary

Introduction

The vast majority of plastics end up landfilled or contaminating the natural environment, as the global polymer recycling rate is an embarrassingly low 9% [1]. The problems of plastic recycling were recently highlighted when China imposed an import ban on waste plastic [2], which stalled global recycling efforts [3,4,5]. Part of the problem is that it is costly to separate the numerous types of plastic, and as consumers have no direct financial incentive to do it in conventional centralized recycling, increasingly sophisticated sorting technologies are proposed [7] to reach a circular economy [8,9,10]. Another approach to reach a circular economy for plastic is Distributed Recycling for Additive. In the DRAM methodology, consumers have an economic incentive [11,13] to recycle because they can use their waste as feedstock for a wide range of consumer products that can be produced for a fraction of conventional costs of equivalent products [14,15,16,17]

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