Development of a Universal Thermosetting Putty for High-Performance Bicycle Frames: An Integrated Materials Engineering and Process Optimization Approach

The rapid expansion of the European e-bike market has increased demand for light-weight 6061 aluminum frames with premium cosmetic finishes, highlighting the need for thermally stable surface-leveling materials compatible with high-throughput powder coating. This study aims to develop a universal (the term “universal” refers to a single putty material intended to meet the requirements of both investigated liquid and powder-coating processes within the studied 6061 aluminum e-bike manufacturing environment) conductive epoxy matrix capable of replacing the dual-putty system currently used in industrial production. A two-phase methodology was implemented under real manufacturing conditions. First, an Analytical Hierarchy Process (AHP) evaluated 32 commercial putty–primer combinations against thermal stability, process compatibility, and production cycle requirements, identifying intermediate liquid primers as the main cause of thermal outgassing and coating defects. Second, a comparative experimental validation evaluated selected graphene-reinforced epoxy formulas produced by planetary centrifugal mixing. The best-performing formulation among those evaluated, containing 0.6 vol% graphene nanoplatelets, showed improved electrostatic powder-deposition performance, consistent with enhanced conductive pathways within the modified matrix, while mitigating coating difficulties associated with the Faraday-cage effect, and achieved Class 0 adhesion while maintaining thermal stability at 180 °C. The resulting Technology Readiness Level (TRL) 5 putty, in accordance with NASA’s (National Aeronautics and Space Administration) measuring system, demonstrates the technical feasibility of consolidating the surface finishing process into a single universal matrix, reducing manufacturing complexity, eliminating the dual-material bottleneck, and supporting more efficient and sustainable mass production of aluminum e-bike frames.