Upcycling of waste plasterboard for the synthesis of high-quality gypsum-based 3D printing powder

Abstract

A large number of waste gypsum was reused of low-value or landfilled which caused serious waste of resources. In this study, a high value-added recycling scheme for waste building gypsum to synthesize a 3D printable material with high-precision was designed. The α-hemihydrate gypsum (α-HH) was synthesized from waste plasterboard by the salt solution hydrothermal method. A synergistic optimization strategy was proposed involving the effect of sodium succinate and pH on the morphology and mechanical strength of α-HH. The properties of recycled α-HH were modified to meet the requirements of 3D printing, including fluidity, setting time and green strength. When the modifier dosage is 0.05 wt% and the pH is 5, the best morphology of α-HH crystals with an average aspect ratio of 1.07 (length of 10 μm) are synthesized. The converted product has close interlocking and intergrowth after hydration, which exhibits excellent mechanical strength (25.5 MPa). The 3D printing materials prepared by the composite modification of recycled α gypsum powder has proven to achieve good printable. The print errors smaller than 4% for pore objects larger than 4.0 mm, and satisfactory results are shown in terms of the strength and resolution of printing high detail cavity structures. This work provides a high value-added upcycling scheme for waste building gypsum that has great potentiality for future industrial application.