Effect of TiO₂ on properties of agar-κ-carrageenan films

Agar films, κ-carrageenan films and their blend films were prepared by thermal casting method, and 0.8%(0.8 g/100 g total dry matter) TiO₂ powders were added into the blend films to obtain TiO₂/agar-κ-carrageenan composite films. The four kinds films were tested by SEM, XRD, mechanical properties, light transmittance, opacity and resistance to water. The results show that the mechanical properties, light transmittance, opacity and resistance to water of agar-κ-carrageenan films are between agar films and κ-carrageenan films. Agar and κ-carrageenan have the good blending and the intermolecular forces are formed in the blend films. The tensile strength of TiO₂/agar-κ-carrageenan composite films is 45.44 MPa which is higher than that of the other three films and increases 46.30% compared with the tensile strength (31.06 MPa) of agar-κ-carrageenan films. But the breaking elongation is 15.73% which is smaller than that of the other three films. The strong interaction forces are formed between matrix molecule of composite films and TiO₂. So the tensile strength of the composite films is enhanced. At the same wavelength, the light transmittance of TiO₂/agar-κ-carrageenan composite films is the lowest. In the ultraviolet region of 200-400 nm, the light transmittance of TiO₂/agar-κ-carrageenan composite films is obviously lower than that of the other three films. TiO₂/agar-κ-carrageenan composite films have a significant shielding effect on UV light. But at the 600 nm wavelength, the opacity of TiO₂/agar-κ-carrageenan composite films is 0.96 which is the highest of the four films. The resistance to water of TiO₂/agar-κ-carrageenan composite films is higher than agar-κ-carrageenan films.