Enabling Electrostatic Painting of Automotive Polymers with Low Cost Carbon Nanofibers

Polymer composites are used widely for automotive body panels to save weight, increase fuel efficiency, and eliminate corrosion. Unlike metals, however, structural polymers are not conductive electrically; thus, they are not amenable to the industry standard technique of electrostatic spray painting (ESP). Current methods for adapting polymers to ESP pose serious environmental and economic challenges. Polymers must be coated with a conductive primer requiring the use of environmentally detrimental solvents (volatile organic compounds or VOCs). There are significant capital and operating costs associated with handling and disposal of the primer and its byproducts. Automotive manufacturers must either maintain two separate paint lines (one for metals and one for polymers) or use inefficient offline painting. This is an expensive proposition, because automotive paint lines cost as much as $400 million. A simple, solvent-free method is needed to endow polymers with sufficient electrical conductivity to be painted in the same manner as metals. Applied Science, Inc. (ASI) will overcome these challenges by a dispersing small amount of carbon nanofiber (CNF) in automotive polymers to give them sufficient electrical conductivity for ESP. ASI’s approach will overcome drawbacks of past attempts to use fillers, such as carbon black and carbon fibers, to produce electrically conductive structural polymers. These strategies failed because carbon black degraded mechanical properties and the thick carbon fibers compromised surface finish. CNF, stronger and more conductive than carbon black and 100 times smaller than the carbon fibers, will provide conductivity at extremely low loading and maintain a class-A finish. The technical challenge associated with this approach is achieving the appropriate electrical conductivity and minimal nanofiber concentrations. ASI will use a number of strategies to overcome this challenge, including: controlling CNF surface chemistry, optimizing blending techniques, and exploiting synergies between CNF and other composite constituents. The innovation could produce substantial environmental and economic benefits. According to a recent government study, the ability to electrostatically paint automotive polymers has a net present value of $500 million. This technology also would eliminate about 0.23 pounds of VOCs per vehicle. Beyond automotives, this technology also could be used to produce trucks, boats, aircraft, household appliances, and sporting goods. ASI’s commercialization efforts will be bolstered by its existing relationships with automotive original equipment manufacturers (OEMs), such as General Motors, and their suppliers. During Phase I, ASI will work with one of these entities to expedite the insertion of this innovation into a high-end niche transportation market.