Aidan Vogel*a and Joseph Moniodis b
Recycled PC-ABS was extruded to produce 1.75mm upcycled PC-ABS 3D printing filament. The ideal extrusion temperature was 245°C at an extrusion rate of 100% and an airpath speed of 75%. The filament produced had a consistent diameter 1.66 – 1.76mm.
The mixing or blending of polymers is an area of material science that is growing considerably.[1][2] Mixtures enhance the existing properties of the combined polymers and exhibit novel ones.[1] The blending of Polycarbonate (PC) with Acrylonitrile-Butadiene-Styrene (ABS) aims to combine the toughness and heat-resistance offered by PC along with the ductility and processability offered by ABS.[3][4] The resulting PC-ABS composite exhibits high strength, high stiffness, high heat resistance, and high impact resistance, even at low temperatures.[3]
Extrusion of polymers and polymer blends into 3D printing filament unlocks the potential for recycled polymers to be used in the manufacture of new goods (upcycling).[2] Extrusion conditions for polymer composites depend on multiple factors and composites vary widely, so polymers of the same blend that are produced differently will require different extrusion conditions.[1][2] The purpose of this study is to determine the ideal extrusion conditions to produce an upcycled PC-ABS 3D printing filament with a variation of 0.10 mm that measures between 1.65 – 1.75 mm in diameter.
Results and Discussion
The three variables that determined the overall quality of the extruded filament were: extrusion temperature, extrusion speed and airpath speed. This communication will report on the impact of these variables. A related but dependent variable was the drive speed of the spooler. The general strategy adopted to successfully extrude filament was to first find the ideal extrusion temperature at a slower extrusion rate, then increase the extrusion rate while adjusting the airpath speed. The drive speed was then adjusted according to the extrusion rate. In this communication, the temperature, extrusion rate and airpath speed will be examined in detail, but it is important to note that the drive speed can also impact the quality of the filament as deformations can occur in the spooling process.
Temperature Temperatures were varied in 5°C increments with the extrusion rate reduced to 50%. The results of three chosen temperatures are presented:
235°C: The filament diameter was very inconsistent, with the thickness fluctuating by up to 0.44 mm.
245°C: Filament fluctuations were much less, up to 0.10 mm but often much less (0.02-0.04 mm)
260°C: There were major fluctuations in diameter, up to 0.45 mm. At temperatures higher than this, the filament has a glossy appearance.
The ideal temperature for extrusion PC-ABS was found to be 245°C.
Extrusion Rate and Airpath Speed:
Once an ideal temperature had been determined, the extrusion rate was set to 100% and the airpath speed was varied to determine the ideal cooling rate. The results of these varying airpath speeds are summarised:
55%: The filament initially came out consistent but thin (1.49 – 1.56 mm), and even with the adjustment of the drive speed, proved difficult to extrude because of a swaying effect, although the thickness became more consistent (1.68 – 1.76 mm)
60% - 70%: The filament was more consistent and easier to extrude, but the measured thickness was higher than expected in most experiments (e.g. 1.72 – 1.82 mm, 1.80 – 1.86 mm)
75%: The filament consistency was steady and the thickness optimal at this speed (1.66 – 1.76 mm)
The ideal airpath speed for an extrusion rate of 100% was found to be 75%.
Table 1 shows the ideal extrusion conditions for upcycled PC-ABS. As the material was recycled and did not come with a data sheet, conditions needed to be determined and they may vary across different composites and particle sizes of the polymer. This is important to keep in mind and the results presented here represent the ideal conditions under the circumstances presented. They can, however, be used as a guide to the extrusion of PC-ABS.
One factor that proved crucial in the successful extrusion of the polymer was the drive speed of the spooler. This variation could be up to 0.10 mm on average and adjustment of these speeds needed to match the extrusion rate and be done as the experiment was progressing. While certain parameters can be set for the experiment, it is worth noting that a certain amount of trial and error is needed when adjusting the drive speed.
Materials and Methods
Recycled PC-ABS pellets were purchased from an online supplier. No material data sheet was provided for the polymer blend. Pellet size was an average of 3 mm. Samples of PC-ABS were dried at 90°C in a conventional oven for 2 hours. These were loaded into a Filabot EX2 Extruder with a 1.75 mm nozzle. A Filabot Airpath was used to cool the mixture once it extruded from the nozzle and a Filabot Filament Spooler collected and spooled the resulting filament. Variables adjusted to obtain optimal performance included extrusion temperature, extrusion rate, airpath speed as well as the drive speed of the spooler, which was dependent on the extrusion rate. The filament was measured using a vernier calliper at random points along its length during and directly after the process. After spooling, the filament was dried in a filament dryer for 2 hours and the diameter measured and compared to that of standard available 3D printing filament.
Conclusions
The extrusion of recycled PC-ABS to produce upcycled 3D printing filament was achieved by varying the extrusion temperature, extrusion speed and airpath speed. A related variable which needed to be adjusted was the drive speed of the spooler, which was dependent on the extrusion rate. The ideal conditions were found to be: temperature = 245°C, extrusion rate = 100% and airpath speed = 75%. This produced filament with a consistent diameter of between 1.66 – 1.76 mm.
Notes and references
[1] Abhijit Deshpande, “Polymers: Concepts, Properties, Uses and Sustainability,” https://www.youtube.com/watchv=dyGwLPHkhV4&list=PLyqSpQzTE6M_KQ5MqUkoOqAxxOrdvFOMB&index=33, 2020.
[2] Jim Johnson, “Polymeric Compatibilizers for Blends and Recycled Compounds,” https://www.youtube.com/watch?v=JyCC94CJ8IQ. 2021.
[3] R. Krache and I. Debah, “Some Mechanical and Thermal Properties of PC/ABS Blends,” Materials Sciences and Applications, vol. 02, no. 05, pp. 404–410, 2011, doi: 10.4236/msa.2011.25052.
[4] Stratasys, “PC-ABS Data Sheet PC-ABS FDM Thermoplastic Filament,” https://www.stratasys.com/contentassets/0cbbbe43e9ab4200a16c507eb99ebe7e/mds_fdm_pc-abs_0222a2.pdf. 2022.