Exploring starch casting as an alternative for the manufacturing of thermosetting polymers

This work explores the feasibility of using starch casting, a fabrication technique commonly used in confectionery production, for the manufacturing of thermosetting polymers. The goal of this work is to offer an alternative to fixed molding methods that minimizes tooling cost and waste while maintaining throughput and geometric flexibility. In this method, a positive die geometry is used to imprint molds into a powdered starch bed, leaving negative molds that can be filled with a liquid polymer. A range of polymers were successfully cast using this technique, including an epoxy, polydimethylsiloxane (PDMS), and polyurethane (PU) with $<0.05\mathrm{mm}$ of geometric deviation from the nominal geometry achieved under near-optimal processing conditions. Results indicate that polymer viscosity plays a significant role in the utility of this casting method, with best results achieved with viscosities between 60-120 Pa$\cdot$s, independent of the polymer tested. In addition, limits on mold creation parameters including compaction pressure and starch moisture content were identified, with critical process parameters determined by measuring the geometric fidelity of the cast materials. This work demonstrates the potential to further develop this manufacturing method as an alternative fabrication technique that is an intermediate between the high scalability of traditional casting processes, and the geometric flexibility of additive manufacturing.