Titanium Dioxide Infused Upcycled PC-ABS for Improved Chemical & UV Resistance
Aidan Vogel*a and Joseph Moniodis b
Recycled PC-ABS was infused with a 1:1 mixture of titanium dioxide (TiO2):Talc (hydrous magnesium silicate) to enhance the chemical and UV resistance of the resulting filament. The TiO2:Talc mixture was added at ratios of 1%, 2%, 3%, 4% and 5% and all ratios were successfully extruded. At higher concentrations (4-5%), the tensile strength decreased slightly. The ideal concentration of TiO2:Talc mixture was 2% (1% TiO2 | 1% Talc). At 5% the mixture did not fully melt into the material, with specs of Talc being observable. This made it difficult to extrude and caused extruder jamming.
The term ‘additive package’ is used to describe the mixture of different additives which are added to plastic to achieve a desired performance.[1], [2] The mixture of polymer and additive package can be extruded to produce a 3D printing filament with enhanced properties. There are many types of additives used in plastics to achieve desired properties.[3] These include plasticizers, flame retardants, stabilizers (chemical, UV, heat), colorants, fillers and reinforcers.[1]–[3]
PC-ABS is an engineering grade polymer with potential applications in construction.[4], [5] It has high strength, stiffness, heat and impact resistance. However, it is prone to UV, chemical and oxidation degradation.[4] In our previous two communications, we have attempted to extrude filament with additives that contribute to UV and chemical stability. In the first of these experiments,[6] PC-ABS with titanium dioxide was successfully extruded to produce 3D printing filament, with the ideal concentration found to be 2% w/w TiO2. In the second experiment, we attempted to extrude PC-ABS with between 2-5% Talc to address chemical degradation.[7] Extrusion of the Talc-infused PC-ABS 3D printing filament was successful. Once again, the ideal concentration was around 2%. In this experiment, we attempted to extrude PC-ABS with an additive package of 1:1 TiO2:Talc at concentrations of between 1-5%.
Results and Discussion
Table 1 shows the measured tensile strengths of the filament resulting from the addition of between 1-5% 1:1 TiO2:Talc mixture to upcycled PC-ABS.
This was our first experiment with two additives in the mixture, with a notable decrease in tensile strength observed at all concentrations of the 2-additive matrix. The results in the above table show a relatively stable tensile strength up to 3%. For concentrations of 4-5%, the tensile strength begins to decrease. At 5% TiO2:Talc mixture, specs of talc were visible in the mixture and the extruder jammed. Talc is chemically inert, and problems have been previously observed in its extrusion at higher concentrations.[7] A proposed solution to these problems may be to increase the extrusion temperature.
While TiO2 has had good adhesion to the polymer in past experiments,[6] it was observed to promote the adhesion of talc to PC-ABS in this experiment. This phenomenon was observed at concentrations of 3-4%. At TiO2:Talc concentrations of 3% and above, specs of talc were observed in the resulting filament. At 3%, some parts of the filament were homogenous while others were flaky, and talc could be observed. At 5%, specs of talc were clearly visible.
Further experiments are required to test the impact on other properties of the polymers. This experiment has demonstrated that successful extrusion can be achieved at low percentages (1-3%). This is in line with our previous experiments involving titanium dioxide[6] and talc.[7] Higher percentages would require the use of a twin screw extruder to form PC-ABS-talc pellets prior to extrusion.[8]
Materials and Methods
Recycled PC-ABS pellets were purchased from Carl’s Industrial Salvage Store. No material data sheet was provided for the polymer blend. Pellet size was an average of 3mm. Talc was purchased from Fasco Expoxies Inc and was of 100% purity with a median particle size of 10µm. Titanium dioxide was purchased from HalalEveryDay and was of 100% purity with a particle size of <5µm. A 1:1 TiO2:Talc mixture was prepare beforehand for addition to the polymer. Samples of PC-ABS were dried at 90◦C in a conventional oven for 2 hours. After cooling, silicone spray was applied to the PC-ABS to facilitate the adhesion of the TiO2:Talc mixture. For each experiment, a total of 50g of material was used, with the following weight ratios of talc to PC-ABS mixed by mechanical shaking for approximately 5 minutes until the mixture was evenly dispersed:
1% - 0.5g TiO2:Talc | 49.5g PC-ABS
2% - 1.0g TiO2:Talc | 49.0g PC-ABS
3% - 1.5g TiO2:Talc | 48.5g PC-ABS
2% - 2.0g TiO2:Talc | 48.0g PC-ABS
2% - 2.5g TiO2:Talc | 47.5g PC-ABS
For each experiment, the mixtures were loaded into a Filabot EX2 Extruder with a 1.75mm 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. The extrusion temperature was set at 245◦C with the extrusion rate at 100% and the airpath speed at 83%, and these were varied as required throughout the experiment. The filament thickness was measured using a Filabot Filameasure and was consistent to within 0.1 mm. The tensile strength was then measured using a ShenCe Digital Force Gauge.
Conclusions
The extrusion of TiO2:Talc infused upcycled PC-ABS 3D printing filament was successfully achieved for 1-5% 1:1 TiO2:Talc added. The tensile strengths of the resulting materials showed a decrease as the concentration of TiO2:Talc increased from 1-5%. Tensile strength values were lower in the two-additive matrix than in experiments with just TiO2 or talc. The ideal concentration of mixture was 2%, with inconsistencies observed in the filament at concentration above this level. Chemical resistance and UV testing is needed to determine the ideal concentration of TiO2:Talc required to achieve adequate chemical and UV resistance at a reasonable cost. Further experiments will be needed to optimise the tensile strength with a multi-additive matrix.
Notes and references
[1] Polymer World, “Plastic Additives,” https://www.youtube.com/watch?v=tpztnm2eXbY. Polymer World, 2020.
[2] Abhijit Deshpande, “Polymers: Concepts, Properties, Uses and Sustainability,” https://www.youtube.com/watch?v=dyGwLPHkhV4&list=PLyqSpQzTE6M_KQ5MqUkoOqAxxOrdvFOMB&index=33, 2020.
[3] J. N. Hahladakis, C. A. Velis, R. Weber, E. Iacovidou, and P. Purnell, “An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling,” Journal of Hazardous Materials, vol. 344. Elsevier B.V., pp. 179–199, Feb. 15, 2018. doi: 10.1016/j.jhazmat.2017.10.014.
[4] 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.
[5] Stratasys, “PC-ABS Data Sheet PC-ABS FDM Thermoplastic Filament,” https://www.stratasys.com/contentassets/0cbbbe43e9ab4200a16c507eb99ebe7e/mds_fdm_pc-abs_0222a2.pdf. 2022.
[6] A. Vogel and J. J. Moniodis, “Extruding Titanium Dioxide Infused Upcycled PC-ABS for Improved UV Resistance,” Swyftlyt Communications, 2022.
[7] A. Vogel and J. Moniodis, “Extruding Talc (Hydrous Magnesium Silicate) – Titanium Dioxide Infused Upcycled PC-ABS for Improved Chemical & UV Resistance,” Swyftlyt Communications, 2022.
[8] Jim Johnson, “Polymeric Compatibilizers for Blends and Recycled Compounds,” https://www.youtube.com/watch?v=JyCC94CJ8IQ. 2021.