Mechanical Properties and Structure of Sol-type and Gel-type Gelatine Films

Abstract

FILMS can be prepared from aqueous sols of gelatine either by evaporating off the water slowly at room temperature, when gel formation precedes dehydration, or directly from the sol by maintaining the drying temperature at a sufficiently high level (for example, 60° C.), which defers the development of structure until the drying process is nearing completion. Pinoir and Pouradier¹ showed that thin sol-type films produced in this way were soluble in water at room temperature, whereas the gel-type films merely swelled under the same conditions. They pointed out the significance of their observation in view of the earlier discovery of Katz and his colleagues that gelatine film prepared at room temperature gave a crystalline X-ray powder diagram, whereas that given by the film prepared hot was of the more amorphous type. They inferred that the difference in solubility between the two was caused by the more extensive organization and bonding of chains in the gel type.