COLLEGE OF ENGINEERING Chemical, Biological & Environmental Engineering

Extrusion and Grinding Goal: Develop a process for recycling PLA RECYCLING FOR (PLA) 3D prints to be reused as 3D printing filament Johnathon Hesseltine, Colin Marshall, Wyatt Self School of CBEE Polymer Characterization Laboratory Purpose: Recycling will minimize waste in the growing 3D printing Saturation Characterization market • Determine influence of high moisture content on PLA MFI and response to drying. PLA pellets from EcNow Tech were used for this test. MFI results in “Recycling Process” are not related. Extruding filament onto winder Laboratory mill Saturation DSC, MFI, DSC, MFI, Virgin Pellets 1, 7 and 14 days Oven dry 2, 7 and 21 days used to grind Chamber and mass and mass failed 3D prints Effect of Moisture on MFI Conclusions Figure 1: Figure shows • Moisture content of less than 1% can weight % water vs MFI as increase MFI by over a factor of 4 DSC Results circle markers. Dashed line • Moisture content above 0.4% during DSC testing showed shows the average value extrusion can lead to non-uniform filament that crystallization after oven drying saturated • MFI increased by an average of 9.5% per behavior, glass pellets. Moisture content cycle corresponding to a molecular weight transition and melting of less than 1% can PLA Background decrease of 2.6% Formula temperatures did not increase MFI by over a • • Recycled filament for 3D printing is possible change with moisture factor of 4. Initial with minimal loss of strength content or drying. moisture has little affect on MFI after drying. Future Work • Characterize effect of humidity to • Biodegradable determine drying process needed for • temperature from 40 to Recycling Process TA Q800 DMA Testing effective filament formation 70 °C Dynamic Mechanical Analyzer (DMA) – A three • Develop improved winding system • Melting temperature from 157 and 180 °C point bend test attachment was used to obtain • Adjust printer settings for recycled Challenges: the elastic (storage) and viscous (loss) moduli. filament • PLA absorbs moisture which breaks down polymer upon heating Acknowledgments • PLA is highly variable, depending on • Skip Rochefort– Project sponsor • Cody Rucker– MFI and grinder training factors such as grade and manufacturer • EcNow Team (Noah Pearson, Nathaniel McArthur, Tristan Figure 2: Shows the recycle process. Moisture 3D printing succeeded using the 1st and 5th Knopf, Le Zhou)– Supplying virgin PLA • Dan Foster- DSC and TGA training control can be oven drying or humidity control. cycles. The printed rectangular bars could be • Britany Swann- Logistical assistance tested using the DMA three point bend test • Justin Pommerenck and Yokochi Lab- Assistance with 3D printing • Ehsan Taghizadeh- DMA training and assistance • Phil Harding– Project guidance

Virgin PLA Pellets Ground Failed Prints Successful 3D print from recycled Terminology material! • Differential Scanning Calorimetry (DSC) – Heat cycles to determine glass transition and melting temperature • Melt Flow Index (MFI) – Forces melted Figure 3: Shows results for multiple recycle Figure 4: Figure shows temperature (°C) vs polymer through a capillary to determine processes (note that 3D printing step was elastic modulus (MPa) and tan δ. Lines show viscosity, which correlates to molecular skipped due to filament limitations). highest quality print, 3D printing variation led weight MFI increased by an average of 9.5% per cycle to differences in results. • Extrusion – Polymer is melted and forced corresponding to a molecular weight decrease Recycling decreases elastic modulus. Print through a nozzle which produces filament of 2.6%. quality impacts elastic modulus.