Formulation and Evaluation of Carbon Black 3D Printing Materials

Abstract

The availability of additive manufacturing and 3D printing capabilities have become widespread in recent years, with multiple commercial vendors offering a wide variety of printing technology and printing materials. Commercial and open-source software enabling 3D model design and editing has become widely accessible as well. The ability to customize and rapidly generate physical parts and tools has the potential to revolutionize logistics supply chains and manufacturing processes. This study was scoped to provide an initial look at the potential of producing electrically conductive filaments that could be used in commercial 3D printers for the purpose of enhancing production of anodes and cathodes for use in benthic microbial fuel cells (MFCs). Microbial fuel cells were identified as a potential application that could benefit from the rapid prototyping and manufacturing that a carbon-doped plastic could provide. Sediment microbial fuel cells (SMFCs) are currently being tested at large scales with moderate success. These systems utilize the electrochemical gradient between anaerobic sediment and oxygenated seawater to produce electrical power. The majority of large systems that are being tested now require handling of carbon materials that can be difficult to process (cut, sew, manipulate, etc.) and may often be an irritant to handlers. As an alternative, conductive plastics can offer a rapid method of manufacturing and prototyping that could easily produce different electrode configurations for testing. Different carbon and plastic materials could also easily be tested and compared using a standardized set of electrode models. Larger systems could be built from smaller subunits fabricated with automated manufacturing processes, further decreasing the cost of these systems. This study investigates the effects of mixing carbon black (CB) as the conductive material with acrylonitrile butadiene styrene (ABS), one of the most common and stable 3D printing materials. The goal here was to develop a methodology for controlling the conductivity of the resulting conductive plastic and evaluate the effects of carbon doping on plastic strength and resistivity. The methodology for making the carbon-infused filament was based off a published report [1]. We have adapted principles of that method to use a commercial carbon black additive (Vulcan XC72, Cabot Corporation, Alpharetta, GA) and acrylonitrile butadiene styrene (ABS). Five separate solutions containing five different concentrations of carbon black were made: 15, 20, 25, 30, and 50 grams of carbon black. In terms of percent carbon black to ABS: 13, 16.7, 20, 23.1, and 33, respectively. The solutions were poured into watch-glasses or glass beakers (Fig. 3 & 4). Watch glasses were placed into an 80 degrees Celsius hot water bath to expedite acetone evaporation. Once the acetone evaporates, it leaves behind a carbon-infused plastic. This plastic is chopped up and extruded to make 3D-printable filament. These anode prototypes were evaluated against commercial conductive polylactic acid (PLA) filament and carbon cloth for strength, resistivity, and MFC performance. The carbon-doped filament with 13 percent carbon performed best in the strength test. Carbon cloth, commercial PLA, and 23.1 percent carbon-infused filament had the lowest resistivity values (in increasing order). The MFC experiment produced more power from the carbon cloth anodes and the 23.1 percent carbon-infused filament; the commercial PLA performed the worst. The carbon-doped filament proves to be a valuable alternative to carbon cloth material for MFC applications.