Reprint: Closed-Loop Materials Flow in Additive Manufacturing

Overview

Polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) are the two most common materials used in three-dimensional (3D) printing, a rapidly expanding industry currently valued at $17.4B. Unfortunately, PLA and ABS are classified as Type 7/“Other” plastic, and thus cannot be recycled by conventional means. Moreover, due to a waste rate of ~30-50% in the 3D printing industry, thousands of tons of 3D-printed materials are discarded annually. In this project, we developed a novel, cost-effective, and environmentally friendly closed-loop solution to scalably recycle these plastics. First, we evaluated the densities, tensile properties, impact strength, and melt flow indices of more than ten different types of 3D-printed PLA and ABS waste materials, as well as their mixtures. We then designed a density-based separation process that leverages an inexpensive, readily available, and non-toxic sodium chloride (NaCl) solution to separate PLA and ABS in the waste mixture. Ultimately, we developed a method to extrude and regenerate high-quality 3D printing filament consisting of 100% recycled PLA and ABS (rPLA and rABS). While the individual extrusion processes for recycled PLA and ABS were unsuccessful in producing high-quality 3D printing filament due to issues such as moisture bubbles, inconsistent thickness, and brittleness, a specific combination of PLA and ABS yielded high-quality, smooth, and printable filament. Our recycling method is both environmentally friendly and cost-effective, providing significant advantages over the currently prevalent chemical recycling methods that are capital-intensive and pollution-generating, as well as the practice of using a high percentage of virgin materials (>30%).

Competition history

• AJAS 2024 Category not listed

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