Freezing–thawing effects on the properties of dialdehyde carboxymethyl cellulose crosslinked gelatin-MMT composite films

Freezing–thawing is used as a new method to disperse montmorillonite (MMT) in dialdehyde carboxymethyl cellulose (DCMC) crosslinked gelatin-based films. The effects of freezing–thawing on the structure and properties of gelatin-DCMC-MMT films were investigated. The data of XRD indicate that freezing–thawing plays an important role in dispersing MMT into gelatin matrix and reducing the nanoparticles aggregation. The optical properties studies show that gelatin-DCMC-MMT films are very transparent and have excellent barrier properties against UV light. Freezing–thawing process decreases the transparency of films at visible region due to the better dispersion of MMT. The resulting films exhibit similar total soluble matter (TSM) values. However, the films prepared by freezing–thawing method have higher moisture content (MC), may be resulting from the more void volume obtained during the freezing–thawing process. The water vapor permeability (WVP) measurements show that the addition of MMT decreases the WVP of the films. Moreover, the freezing–thawing method can further decrease the WVP of the films. In addition, the films prepared by freezing–thawing are observed with better mechanical properties and thermal stability. The results suggest that the freezing–thawing method is beneficial to dispersing MMT into the gelatin matrix and raising the properties of DCMC crosslinked gelatin-MMT films.