| 摘要 |
<p>A modified calcium sulfate composition is disclosed which when hydrated possesses unique fracture properties of particular advantage when the material is used as a composition for making molds particularly for use in the lost wax process, the composition comprising, a) as a major constituent, calcined gypsum suitable for curing by hydration, b) as a minor constituent, extender capable of holding in the final composition a volume of water at least equal to the volume of the added extender, and c) as a minor constituent, water dispersible binder capable of enhancing the adherence of the added extender in the final composition to the hydrated gypsum, the constituents being present in proportions selected to impart rigidity and a smooth surface to the cured composition while producing a strength under compression of less the 500 psi.</p> |
