Study On Interaction Mechanism And Properties Of Gelatin-montmorillonite

As a natural amphoteric polyelectrolyte, the chains of gelatin possess large amounts of positive and negative charges. Montmorillonite(MMT) is a kind of natural layered silicate, the distribution of charges on its layers is also very complicated. All these determine that the interaction between gelatin and MMT is special. According to the characteristic of intercalation, modifying gelatin with surfactant (Surf) before intercalation with MMT will influence the effect of intercalation and the properties of the materials. This study has both the theoretical and practical merits for enriching intercalation theory and opening up a new path for high-performance of proteins such as gelatin. In this paper, in order to ascertain the process of intercalation, the product of intercalation was characterized by means of X-Ray Diffraction, Atomic Absorption Spectroscopy, Thermogravimetric analysis. The thermodynamics of intercalation was analyzed by changing the conditions of intercalation(such as the ratio of gelatin to MMT, concentration, the pH of gelatin solution, reaction temperature). The results indicated that, the reaction of intercalation proceeds very fast, the product is under thermodynamics-stable state after five minutes. The amounts of gelatin which intercalate into the interlayers of MMT is also fixed. Except reaction temperature, all the other reaction conditions could affect the structure of production, the intercalation process is controlled by enthalpy. With the aid of Ultraviolet Spectrophotometry, Particle Size Analyzer, Conductivity Analyzer, the parameters in the interaction process between gelatin and MMT were measured. Meanwhile, the effect of reaction conditions on the interaction process was studied. The results indicated that, as soon as the contact of gelatin and MMT, coagulation occurs, then decoagulation and desorption occurs. The process of desorption can be described with a second order rate equation. The decrease of reaction temperature, the ratio of gelatin to MMT, the pH of gelatin solution will decrease the rate of desorption. Surfactants were interacted with gelatin under different conditions (the kind of the surfactant, the concentration of the surfactant, pH of the gelatin), the gelatin -surfactant complex was intercalated with MMT and formed gelatin-surfactant/MMT composite. The swelling and mechanical properties were tested; the factors that affect the properties of composite were analyzed. The results indicated that, gelatin-surf complex can intercalated into MMT sheets, and furthermore, the maximal basal spacing even reaches 4.5nm, the effect of the intercalation was improved significantly. While the pH of gelatin lower than its pI and the concentration of CTAB higher than its CMC, the gelatin-CTAB/MMT composite has the lowest equilibrium swelling degree and the best mechanical property.