Functional Filaments: Creating and Degrading pH-Indicating PLA Filaments for 3D Printing

Abstract

With the rapid pace of advancements in additive manufacturing and techniques such as fused filament fabrication (FFF), the feedstocks used in these techniques should advance as well. While available filaments can be used to print highly customizable parts, the creation of the end part is often the only function of a given feedstock. In this study, novel FFF filaments with inherent environmental sensing functionalities were created by melt-blending poly(lactic acid) (PLA), poly(ethylene glycol) (PEG), and pH indicator powders (bromothymol blue, phenolphthalein, and thymol blue). The new PLA-PEG-indicator filaments were universally more crystalline than the PLA-only filaments (33–41% vs. 19% crystallinity), but changes in thermal stability and mechanical characteristics depended upon the indicator used; filaments containing bromothymol blue and thymol blue were more thermally stable, had higher tensile strength, and were less ductile than PLA-only filaments, while filaments containing phenolphthalein were less thermally stable, had lower tensile strength, and were more ductile. When the indicator-filled filaments were exposed to acidic, neutral, and basic solutions, all filaments functioned as effective pH sensors, though the bromothymol blue-containing filament was only successful as a base indicator. The biodegradability of the new filaments was evaluated by characterizing filament samples after aging in soil and soil slurry mixtures; the amount of physical deterioration and changes in filament crystallinity suggested that the bromothymol blue filament degraded faster than PLA-only filaments, while the phenolphthalein and thymol blue filaments saw decreases in degradation rates.

Development of active biocomposite films based on poly(lactic acid) and wine by‐product: Effect of grape pomace content and extrusion temperature

“…On the other hand, PLA showed a single‐step degradation between 310 and 390°C, with 50% weight loss at 365°C. This result is similar to those obtained by other researchers for the thermal depolymerization of PLA 36 . A single‐stage degradation was also observed for GP/PLA biocomposites.…”

“…Neat PLA showed an elastic modulus between 1654 and 2360 MPa, a tensile strength around between 41 and 45 MPa, and elongation at break between 8% and 9%. All these values were within the range reported in literature for PLA 29,36 . Elastic modulus decreased significantly when the GP concentration in the PLA increased.…”

“…35 On the other hand, PLA showed a single-step degradation between 310 and 390 C, with 50% weight loss at 365 C. This result is similar to those obtained by other researchers for the thermal depolymerization of PLA. 36 A single-stage degradation was also observed for GP/PLA biocomposites. However, the incorporation of GP resulted in a reduction of 50-60 C from the degradation temperature of PLA, which demonstrated the accelerating effect of GP in the polymer degradation.…”

“…All these values were within the range reported in literature for PLA. 29,36 Elastic modulus decreased significantly when the GP concentration in the PLA increased. As was postulated in DSC analysis, GP could create free volume in the PLA matrix showing a plasticizer effect that consequently improved the flexibility of the material.…”

Boron‐polymer composites engineered for compression molding, foaming, and additive manufacturing

“…ABS composite filaments (ABS‐PEG‐B) contained 30 wt% boron, 10 wt% PEG, and 60 wt% ABS. PEG was used as an additive to reduce brittleness caused by high concentrations of powdered filler material 33 . Filaments were fabricated by melt‐blending the mixed materials in a twin‐screw microcompounder (Xplore MC 40; Xplore Instruments BV, The Netherlands).…”