Experimental Paste-paste Type Phosphate-bonded Investment with Colloidal Silica Solution

抄録

Although silica is the most popular refractory material, it is known that inhaled silica powder can induce lung or respiratory diseases, potentially leading to cancer. The purpose of this study was to develop experimental paste-type phosphate-bonded investments fabricated with colloidal silica solutions. Paste 1 was prepared by mixing cristobalite powder of 80 g with 30 cc monomagnesium phosphate solution. To investigate the effects of colloidal silica solution within paste 2, three volumes (A: 20 cc, B: 25 cc, C: 30 cc) were prepared with 15 g of MgO each. Basic properties and fit of the casting were compared to commercial phosphate-bonded investment and evaluated. The setting times for A, B and C were statistically different. The quickest setting time was measured from U. The fired strength of U was remarkably greater than those of others. The setting expansion of U was obviously greater than those of the experimental investments. The average value of A was statistically higher than that for B. C expanded minimally while setting. The expansion percentages at 850ºC were no significant differences among experimental investments. In addition, that of U during the entire heating was remarkably low. The degree of the fit differed significantly between U and A because setting expansion of A was insufficient. Although the results are not optimal, the newly developed paste-paste type phosphate-bonded investments produced in this study still offer potential as alternative investment systems due to their excellent fluidity, manipulation and reasonable basic properties.