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 [Figure presented] as determined by differential scanning calorimetry (DSC). The maximum stiffening rate of [Figure presented] and maximum storage modulus of [Figure presented] 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 [Figure presented] in [Figure presented]. The following carbonation hardening of [Figure presented] leads to a final compressive strength of [Figure presented] at a porosity of [Figure presented].