Published 16th December 2022 Aidan Vogel*a and Joseph Moniodis b
Recycled PC-ABS was infused with titanium dioxide to enhance the UV resistance of the resulting filament. Titanium dioxide was added at ratios of 1%, 2%, 3%, 4% and 5% and all ratios were successfully extruded with a very slight decrease in mechanical strength as the concentration of TiO2 was increased. UV testing is required to measure the UV resistance at each level of TiO2 and determine whether an appropriate level of UV tolerance is achievable with no observed decrease in mechanical strength.
Most polymers are inherently weak, which makes them susceptible to degradation under extreme conditions.[1] The addition of functional additives can improve the properties of the resulting product.[1],[2] The resulting polymer blends exhibit application potential in the building industry because of their excellent properties, compared to inorganic materials. Polymers blended with functional additives are waterproof, corrosion resistant, wear resistant, antiseismic, lightweight, mechanically strong, sound insulators, heat insulators, good electrical insulators, and brightly colored.[2],[3]
Building materials have an expected lifespan of 50 years, while for civil engineering materials, it is 200+ years.[1] This makes the additive matrix in such materials crucial for their longevity.[1] There are many different additives used to enhance the properties of polymers and polymer blends.[1],[2]
PC-ABS is an engineering grade polymer that exhibits high strength, high stiffness, high heat resistance, and high impact resistance, even at low temperatures.[4]–[6] However, it has poor weatherability and low fatigue endurance, as well as low chemical, UV and oxidation resistance.[5] Titanium dioxide has been shown to improve the weatherability and UV resistance of polymers.[7],[8] In this experiment, we aim to test the
effect of adding between 1-5% TiO2 on the tensile strength of our upcycled PC-ABS 3D printing filament to determine whether the addition of TiO2 has a measurable impact on the tensile strength of the polymer blend.
Results and Discussion
Table 1 shows the measured tensile strengths of the filament resulting from the addition of between 1-5% titanium dioxide to upcycled PC-ABS.
Table 1 – Tensile strength of resulting PC-ABS filament that contained between 1-5% titanium dioxide.
The results show a very gradual decrease in the tensile strength as the concentration of TiO2 is increased from 1 to 5 %. However, filament diameter can vary by up to 0.1mm, which represents a 5.6% deviance. This means that the measured tensile strength can vary by up to 5.6% across the same sample. The range of variation in tensile strength as the concentration of TiO2 is increased falls within this range, so more work will need to be done to measure the exact nature of the observed trend.
It was observed that at concentration of 4 and 5%, a significant amount of TiO2 had not attached to the polymer at the mixing stage, and was poured into the hopper and mixed there. This could be due to saturation of the additive under these conditions. The difference in particle size, 3mm (PC-ABS) vs <5µm (TiO2) may have something to do with this. The problem of particle size differential has been identified in previous literature.[9] It has been discovered that when pellets and powders are combined, it is only possible to mix single digit
percentages before saturation is reached. This has been hypothesized to result from powder on the surface of the pellets likely impeding the adhesion of the pellets against the wall of the extruder and the formation of the melt film. As a result, less shear stress is applied, the pellets are not broken down into smaller particles, and their heart probably remains unmelted. The same work noted that the mixing of two powders resulted in the successful addition of up to 20% additive.
Burn et al.[8] observed that the best weatherability for UPVC pipe over a period of 2 years was obtained at a concentration of 2% w/w TiO2. Mohr et al.[7] observed that a concentration of 5% TiO2 w/w in polylactic acid biodegradable polymer achieved the best UV blocking. Tests will need to be performed to determine the ideal improvement in weatherability in this case, however, these studies indicate that it will fall between 2-5%.
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 3mm. Titanium dioxide was purchased from HalalEveryDay and was of 100% purity with a particle size of <5µm. Samples of PC-ABS were dried at 90◦C in a conventional oven for 2 hours. For each experiment, a total of 50g of material was used, with the following weight ratios of titanium dioxide to PC-ABS mixed by mechanical shaking for approximately 5 minutes until the mixture was evenly dispersed:
1% - 0.5g TiO2 | 49.5g PC-ABS
2% - 1.0g TiO2 | 49.0g PC-ABS
3% - 1.5g TiO2 | 48.5g PC-ABS
2% - 2.0g TiO2 | 48.0g PC-ABS
2% - 2.5g TiO2 | 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%. 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 titanium dioxide infused upcycled PC-ABS 3D printing filament was successfully achieved for 1-5% TiO2 added. The tensile strengths of the resulting materials showed a slight decrease as the concentration of TiO2 increased from 1-5%. UV testing is needed to determine the ideal concentration of TiO2 required to achieve adequate weatherability at a reasonable cost. Further tests may also be needed to ensure the observed trend is reproducible and attain a more accurate measure of the slope of the observed decrease.
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&in dex=33, 2020.
[3] J. Shen, J. Liang, X. Lin, H. Lin, J. Yu, and Z. Yang,
“Recent progress in polymer-based building materials,” Int J Polym Sci, vol. 2020, 2020, doi: 10.1155/2020/8838160.
[4] Stratasys, “PC-ABS Data Sheet PC-ABS FDM
Thermoplastic Filament,” https://www.stratasys.com/contentassets/0cbbbe43 e9ab4200a16c507eb99ebe7e/mds_fdm_pc-abs_0222a2.pdf. 2022.
[5] F. Radius, “Know your materials:
Polycarbonate/acrylonitrile butadiene styrene (PC-
ABS),” Fast Radius Website, 2021.
[6] 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.
[7] L. C. Mohr, A. P. Capelezzo, C. R. D. M. Baretta, M. A. P. M. Martins, M. A. Fiori, and J. M. M. Mello,
“Titanium dioxide nanoparticles applied as ultraviolet radiation blocker in the polylactic acid bidegradable polymer,” Polym Test, vol. 77, p. 105867, Aug. 2019, doi: 10.1016/J.POLYMERTESTING.2019.04.014.
[8] L. Burn, K. G. Martin, and D. Terrill, “Effects of
Titanium Dioxide on the weathering performance of
UPVC Pipe,” CSIRO, 1987.
[9] 3devo, “PLA + Aluminium,” 3devo Journal, 2019.
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