Cure Kinetics and Thermal Behavior of a Printable Polydimethylsiloxane-Based Polymer

In this study, we investigate the curing reaction kinetics and degree of cross-linking of LL50, a polydimethylsiloxane (PDMS)-based polymer, using isothermal heat flow calorimetry (HFC). LL50, developed by Lawrence Livermore National Laboratory, is a two-part addition-curing liquid silicone rubber for direct-ink-writing additive manufacturing. The curing process, driven by a platinum-catalyzed hydrosilylation reaction, was monitored under isothermal conditions at various temperatures. We developed a kinetic model to predict the curing rate and extent of the reaction. The model was validated within the temperature range of 50 to 80 °C, showing good agreement with experimental data. However, the model's extrapolation to near-room temperatures (30 °C) was less accurate, indicating that different kinetic mechanisms may be at play. Our findings highlight the importance of validating kinetic models across relevant temperature ranges and underscore the utility of isothermal calorimetry in studying polymer curing processes. This study provides insights into the processing conditions necessary for the optimal performance of LL50 in 3D printing applications.