Preparation and characterization of nano-SiO2 reinforced gelatin-k-carrageenan biocomposites.

The main goal of this study was to prepare bionanocomposites by combination of gelatin (10% w/v), k-carrageenan (0.5%) and nano-SiO2 (1, 3 or 5%). Then, mechanical properties (tensile strength, elongation at break, Young's modulus), gas permeability (water vapor, oxygen), water solubility, color, UV-vis transmission/absorbance, water vapor adsorption isotherms and Fourier transform infrared (FTIR) analysis of nanocomposites were evaluated. As the results indicated, inclusion of nano-SiO2 (at each level) could increase tensile strength and Young's modulus significantly, with the latter becoming nearly 110% higher at 5% nanoparticle level compared with gelatin-carrageenan biocompostes. Furthermore, incorporation of 5% nano-SiO2 could decrease water vapor permeability of biocomposites from 8.9 to 1.6 × 10-11 g m-1 s-1 Pa-1 and their oxygen permeability from 226 to 97 cm3 μm m-2 day-1 atm-1. Water vapor adsorption isotherms revealed that the water activity of 0.5 was the critical point beyond which the difference in equilibrium moisture content between nanoparticle-incorporated films and biocomposites increased considerably. Besides, this research demonstrated that including 5% of nano-SiO2 is a good solution to delay UV light driven reactions as it elevated absorbance of UV light (220 nm) by biocomposites up to 4 times.