Mechanical properties of gelatin films cross-linked, respectively, by ferulic acid and tannin acid

Gelatin films were cross-linked, respectively, by ferulic acid and tannin acid obtained from plant kingdom. Influences of concentrations of cross-linking agents and pH values of film-forming solution on the mechanical properties, swelling properties and water vapor permeability of gelatin films were investigated in details. And influence of storage time on the properties of treated gelatin films was studied as well. UV-Vis absorption spectra and scanning electron microscopy (SEM) were applied to observe the changes of gelatin films after modified in order to explore primarily cross-linking mechanism. The results showed: (1) that the two natural cross-linking agents had cross-linking effects on gelatin film; (2) that the maximal mechanical strength of gelatin film could be obtained when the pH value of film-forming solution was 7 for ferulic acid as cross-linked agent, or when the pH value was 9 as for tannin acid; (3) that the cross-linking agents could decrease swelling ratios of the films but there were no obvious effects on water vapor permeability; and (4) that the properties of films treated by tannin acid could become better after stored for more than 90 days, while storage time had little effect on ferulic acid-modified films.