Photochemical Foaming and Kinetic Characterization of an Energetic Monomer System for Engineered Porous Propellants

Foamed polymers are widely used for shock absorption and packaging, with typical densities ranging from 0.1 to 0.4 g/cm³. Higher densities (>0.4 g/cm³) are desirable for propellants requiring engineered surface area progression for enhanced combustion. This work explores material development toward additive manufacturing, coupled with a tuneable foaming method, to achieve such structures. Vat-photo polymerization offers layer-by-layer control while the incorporation of a photoacid generator (PAG) to decompose calcium carbonate (CaCO₃) during printing enables pore formation. This approach avoids the need for pressure or elevated temperature. This work reviews the effects of the PAG on polymerization kinetics and the resulting foam structure, enabling the generation of highly engineered foam architecture for tailorable gas generation rates and improved piezometric efficiency in gun propulsion. Building upon this foundation, additional studies have provided deeper insights into the foaming mechanism. UV–vis spectroscopy of relevant ingredients has allowed for a detailed analysis of their light absorption characteristics. Critically, photo-DSC analysis has quantified the photopolymerization kinetics during the foaming process and initial analysis using a photo rheometer, revealing key relationships between processing parameters and the resulting foam structure.