3D printing of High-Strength Silicone-Based Polyurethane-Polyurea enabled by growth of covalent Cross-Linked network

In this study, a two-step chemical reaction is designed in 3D printing process for fabricating polysiloxane-based polyurethane-polyurea (PSURA) 3D products with a high strength and ductility. First, an acrylic and -NCO groups-containing polysiloxane-based polyurethane (PSUA) prepolymer with good flowability is synthesized and printed into the desired 3D structure under UV irradiation. Subsequently, the residual -NCO groups in UVcrosslinked PSUA react with chain extender, resulting in the chemical growth of the crosslinked polymer network. This process significantly reinforces and toughens the printed products by increasing their molecular weight and introducing multiple hydrogen bonds. The tensile strength and elongation at break of the cured PSUA ink can be significantly increased by 330% and 60%, respectively. Due to hydrogen bond dissipation of matrix and buckling of cellular structure under compression, the printed foam with desirable structure exhibits a large energy dissipation for reducing the impact force by 68.9%, which surpasses commercial protective materials.