Abstract
Bionanocomposite materials have been designed as a promising route to enhance biopolymer properties, especially for food packaging application. The present study reports the preparation of bionanocomposite films of alginate with different loadings of pure reduced graphene oxide (rGO) or of mixed zinc oxide-rGO (ZnO-rGO) fillers by solvent casting. Sepiolite is used to make compatible rGO with the hydrophilic matrix. The addition of fillers to alginate matrix maintains the low water solubility promoted by the calcium chloride treatment, and, additionally, they demonstrate a weaker mechanical properties, and a slight increase in water vapor permeability and wettability. Due to the properties of ZnO-rGO, the alginate bionanocomposites show an increase of electrical conductivity with the increase of filler content. While the highest electrical conductivity (0.1 S/m) is achieved by the in-plane measurement, it is in the through-plane measurement the remarkable enhancement of almost 30 times greater than the alginate film. With 50% of ZnO-rGO filler, the bionanocomposites present the highest antioxidant and antibacterial activities. The combination of electrical conductivity with bioactive properties makes these films promising not only to extend food shelf-life but also to allow packaged food sterilization at low temperature.
Highlights
Bionanocomposite films were prepared by solvent casting from mixtures of aqueous solutions of alginate with reduced graphene oxide (rGO) or zinc oxide-rGO (ZnO-rGO) previously dispersed into the sepiolite fibres
Different amounts of filler were incorporated into the alginate matrix, ranged from 25 to 50% of the alginate weight, which allows the films thickness to increase from 32.3 μm to between 56.1 and 86.6 μm
Alginate films incorporated with rGO or ZnO-rGO fillers, previously dispersed in an aqueous suspension of sepiolite fibres, were produced by solvent casting
Summary
Biopolymers, including polysaccharides, proteins, and lipids, have been regarded as more sustainable materials because they are natural, came from renewable resources and may be biodegradable and compostable, satisfying the current environmental challenges by solving the waste disposal problems to some extent. They can be chemically functionalized and blended with other biodegradable polymers, plasticizers, compatibilizers, and/or active fillers to improve their performance, being good alternatives the petroleum-based polymers in a diversity of applications, from food packaging to biomedical fields [3,4,5]
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