Combined effects of clay minerals and polyethylene glycol in the mechanical and water barrier properties of carboxymethylcellulose films

•Carboxymethylcellulose films with clay nanoparticles prepared by solution casting.•Combined action of clay and polyethylene glycol.•Synergy between CMC + clay + PEG promotes dramatic increase in mechanical and barrier properties.•CMC has better affinity to pure sodium montmorillonite than to organically modified clays. Carboxymethylcellulose (CMC), a biopolymer with good film-forming abilities, has rather poor mechanical and water vapor barrier properties which restrict its use in potential food packaging applications. Aiming to improve these properties, CMC was therefore modified by the addition of polyethylene glycol (PEG) and sodium-based clay nanofillers. The results showed the combined action of PEG and sodium montmorillonite greatly improved the tensile mechanical properties of CMC, increasing simultaneously its modulus (up to 260%), strength (up to 250%) and elongation (up to 300%). The barrier effect promoted by the clay nanoplatelets in combination with PEG also resulted in an almost fivefold decrease in water vapor permeability. With these improvements, the use of CMC in edible food packaging applications becomes more feasible.