Improvement on mechanical strength and water absorption of gypsum modeling material with synthetic polymers

Abstract α- or β-Calcium sulfate hemihydrate (α-H or β-H) are commonly used to make gypsum model for ceramics manufacture as modeling material. Unlike construction gypsum, gypsum model urges both high mechanical strength and water absorption. In this experiment, synthetic polymers were investigated on their effect on the properties of hardened gypsum pieces, focusing on the structure–function relationship. Four sulphur polycarboxylates were designed and synthesized for a comparison study with some commercial polymers. It was found that all assayed sulphur polycarboxylates could maintain or improve water absorption of the hardened gypsum pieces made from β-H, but only the one without carboxyl group led an increase of the mechanical strength; the more hydrophilic polymers enhanced the mechanical strength and water absorption even at a ratio of water to hemihydrate (W/H) as high as 0.7. The results suggest that keeping sulphur and vinyl alcohol residues in the molecular will be a promising design for polymer structure applied in gypsum modeling material.