BS in Materials Engineering
Materials Engineering Department
This exploratory study developed methods of manufacturing and characterizing the electrical properties of small batches of conductive composite feedstock for the Fused Deposition Modeling (FDM) manufacturing process, commonly known as 3D printing. We utilized a solution casting process of Poly(lactic acid) (PLA) (Grade 4043D, NatureWorks, LLC.) and Carbon Black (CB) (Vulcan® XC72, Cabot Corp.) in chloroform. The resulting composite precursor was cryogenically treated with liquid nitrogen and milled in a coffee grinder in order to achieve particles that could be fed into the extruder. Composite precursors were dried in a vacuum oven at an elevated temperature of 38°C. Filaments were produced via filament extruder (Filastruder 2.0). Volume resistivity was measured using a modified method of ASTM D991-89 with a customized test fixture. Compositions ranging from 0.1 to 45 vol% of CB were manufactured in this way. Results indicated that compositions of 25 vol% and 30 vol% CB showed regions of conductivity in the filament, however their conductivities were highly inconsistent, with lengths of filament having both conductive and nonconductive regions. Regions that did conduct were ohmic, with volume resistivities ranging from 1.4 to 63 * 10-2 ohm*m. Samples with concentrations of 35 vol% and greater were unable to be extruded effectively due to the limitations of the equipment available.