ABSTRACT

Semicrystalline polymer networks offer valuable shape-memory and shape-shifting properties; however, material processing and scale-up remain major challenges. A laboratory-scale reaction injection molding (RIM) apparatus and methodology are described to mold and cure urethane linked poly(caprolactone) networks from commercially available polyols and polyisocyanate. The highly customized RIM system is capable of making small shot sizes (∼39 g) at precise stoichiometric ratios and forming elastomers with low run-to-run variation of mechanical properties. Experiments conducted with a dye in one feed stream enable evaluation of mixing efficacy, and component mixing is substantially improved by recirculating reagents at higher pressures. Networks prepared with excess isocyanate exhibited higher modulus, which is most likely due to the formation of allophanates.

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