Blend films from sodium alginate and gelatin solutions

Blend films were prepared by blending 4 wt% sodium alginate and 5 wt% gelatin aqueous solutions and dried at room temperature for 2 days to obtain the transparent films. Their structures and properties were studied by infrared (IR) spectra, wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Significant changes in the shape and intensity of IR spectra absorption frequencies characteristic of either gelatin or sodium alginate were detected by IR analysis. The crystallinities of the blend films decreased with the increase of sodium alginate content. The thermal stability, mechanical properties of tensile strength, and breaking elongation of the blend films were improved by blending sodium alginate with gelatin. It is worth noting that the breaking elongation reached 16.6% when the weight ratio of sodium alginate to gelatin was 1:1, much higher than that of two components. The structure analysis indicated that there is strong interaction between sodium alginate and gelatin molecules resulted from intermolecular hydrogen bonds and ionic interactions. The water absorbability of the blend films was improved due to the introduction of sodium alginate.