Gelatin Improves the Physical Properties of Sodium Alginate Hydrogel Films

This study aimed to solve the problems of Ca²⁺ crosslinked sodium alginate hydrogel film, such as easy syneresis, single three-dimensional network structure, and poor thermomechanical properties. Specifically, sodium alginate and gelatin were used as filming substrates, calcium carbonate and gluconolactone were used as crosslinking agents to prepare hydrogel films by casting method. To investigate the effects of different ratios of gelatin or sodium alginate (0:6, 1:6, 2:6, 3:6, 4:6, 5:6) on the hydrogel films physical performance. In this experiment, the intermolecular forces of hydrogel films were analyzed by Fourier transform infrared spectroscopy, and the physical properties of hydrogel films were characterized by microstructure, swelling ratio, gel fraction, water contact angle, mechanical properties and thermal properties. The results showed that the interaction between gelatin and sodium alginate was mainly hydrogen bonding and polyelectrolyte interaction. The introduction of gelatin effectively improved the three-dimensional network structure of the single sodium alginate hydrogel film, increased the gel fraction and hydrophobicity of the hydrogel film, and enhanced the mechanical properties and thermal properties of the hydrogel film. However, the ratio of gelatin/sodium alginate was too high resulting in poor compatibility and mechanical properties of gelatin and sodium alginate. In summary, the tensile strength (29.6 MPa), elastic modulus (164.99 MPa), gel fraction (38.91%) and swelling ratio (2942.50%) of the hydrogel film were optimal when the ratio of gelatin/sodium alginate was 3:6, at which time the physical properties of the hydrogel film were optimal and had potential applications in many fields.