Effect of low concentrations of SiO2 nanoparticles on the physical and chemical properties of sodium alginate-based films.

This work investigated the effect of adding low concentrations of nano-SiO2 (0.5, 1.0 and 1.5%) in the properties of films based on sodium alginate, to identify lower thresholds in the proportion of the reinforcing agent. It was found that, even in the smallest proportion, thermal stability of the nanocomposites improved significantly (with degradation onset increased by almost 15% compared with the control film). The surface morphology showed pronounced roughness at nano-SiO2 concentrations greater than 1.0%, indicating agglomeration of part of the nanomaterial. Mechanical properties were reduced for the samples with concentrations equal to 1.0 and 1.5%, however, without significant differences between them. Conversely, water vapor and light barrier properties have not undergone significant changes in any formulation. Therefore, the use of 0.5% nano-SiO2 in alginate films would be an easy and economically interesting way to improve thermal stability, without significantly reducing mechanical properties of the pure material.