Solvent extraction thermal diffusion results

To create an initial porous structure before thermal binder removal, it is also possible to extract parts of the binder system by solvent extraction. In this technique the ceramic green bodies are immersed in a liquid which solvates one of the components in the binder used. A prerequisite of this process is that the binder component to be removed first has a high solubility in the solvent to ensure rapid dissolution. Furthermore the viscosity of the resulting polymer solution should be low, and diffusion of the liquid inside the body should be fast. Swelling of the binder components during solvent extraction can cause defects to be formed inside the ceramic body because of the internal stresses generated. Solvent extraction is a relatively fast and the cost of the equipment relatively low. 

Examples of the resulting plots of the desorption rate vs. temperature are shown in Figure 12. Untreated corneum samples exhibit one maximum at about 80°C whereas ether extraction (90 min) produces a second lower temperature maximum in addition to the higher temperature peak. The low temperature peak perhaps indicates the presence of loosely bound water which can diffuse out of the corneum more easily than the primary sorbed water. The thermogram for the chloroform-methanol-extracted corneum reveals a single, broad peak indicative of a more general solvent damage to the corneum matrix. The thermal de-... 

---