Effect of nanostructured graphene on the physicochemical and mechanical properties of Cassava starch (Manihot esculenta) coated cellulose paperboards

• Graphene-composed cassava starch coatings at different concentrations (0.2 and 0.4 %) were developed. • FTIR and Raman spectra of cassava starch identified its functional groups. • Uncoated and papercoated only with starch were similar in their appearance. • Moisture barrier increased by 87.8 % with starch-containing 0.4 % graphene. • Water absorption capacity increased >45 % with starch-containing 0.4 % graphene. Graphene is derived from graphite and consists of pure carbon. It can be used to produce nanostructured compounds that are incorporated in packaging materials to improve physicochemical and mechanical properties. The application of coatings made from natural polymers, such as starch, has been studied as an alternative to partially replace synthetic polymers in paper-based multilayer materials commonly used in packaging, meeting the demands of consumers with increasing environmental concerns. In this work, we describe the first-time use of a modified cassava ( Manihot esculenta ) starch film (4 %, m/V) coating, in which graphene has been incorporated at two different concentrations (0.2 % versus 0.4 % m/V), and characterized for its suitability for the coating of paperboard. The presence of graphene in the coating significantly influenced the physicochemical properties of the coating. The Cobb test indicated greater water retention in the coatings containing graphene, but the moisture barrier increased by 87.8 % with the one composed of 0.4 % graphene. In paperboards coated with starch containing 0.4 % graphene, the air permeance decreased by 27 % and fat barrier properties increased, compared to uncoated paperboard. The Taber stiffness was also improved with the presence of graphene in the coatings, indicating that the paperboards became more rigid. The tear strength and tensile strength of the coated paperboards also improved, while elongation and bursting remained unchanged. With the outcomes of this work, we confirm that starch coating containing graphene offers a promising alternative to polymeric lamination on cellulosic matrices, promoting sustainability in packaging and improving the final properties of the paperboard.