A dual binder concept for 3D printing ink: Triggered polymerization for rapid stiffening and carbonation for final strength

Additive manufacturing or 3D printing of polymeric materials is facilitated by sharp fluid-to-solid transition mechanisms. In contrast to polymeric materials, controlling the fluid-to-solid transition of suspensions based on reactive inorganic binders like cement remains challenging. Here, we present a dual binder suspension with precise control over the fluid-to-solid transition. We combine an organic binder system based on free radical polymerization of acrylic acid with an inorganic binder system based on the carbonation of calcium hydroxide. Once initiated, the polymerization of the organic binder forms a crosslinked polymer network, leading to a rapid fluid-to-solid transition of the material. The onset of polymerization is achieved with a thermal initiator (2,2'-azobis[2-(2-imidazolin-2-yl)propan]dihydrochloride) and could be adjusted in a temperature range of as determined by differential scanning calorimetry (DSC). The maximum stiffening rate of and maximum storage modulus of are obtained by a rheometer using small-angle oscillatory shear (SAOS) experiments. Cubic samples are prepared using microwave irradiation to reach a compressive green body strength of in . The following carbonation hardening of leads to a final compressive strength of at a porosity of . • A hybrid-binder suspension comprising an inorganic and organic component stiffening at a rate of 140 kPa/s. • The inorganic binding phase is carbon-negative as it is based on the reaction of Ca(OH) 2 with CO 2 to form CaCO 3 . • A compressive strength of more than 10 MPa is achieved. • The hybrid suspension is triggerable by heat and suitable as an ink in large-scale 3D printing of structural materials.