Barrier, mechanical and morpho-structural properties of gelatin films with carbon nanotubes addition

• Gelatin films with carbon nanotubes addition at various relative humidities were obtained.
• Barrier, mechanical and morpho-structural properties of gelatin films were measured.
• Tensile strength decreased with relative humidity, while elongation at break increased.
• Carbon nanotubes did not affect film barrier properties, but increased elongation at break.
• Film image analysis showed a film morpho-structure with high ordering level.

The effect of a small amount of carbon nanotubes (CNT) on the water content and physical properties of gelatin films with glycerol were evaluated. Control films and those with 0.001% (w/w) CNT addition were prepared. Water isotherms adsorption and water vapor permeability, were undertaken on the gelatin films to asses barrier characteristics. Tensile strength and elongation at break were evaluated with a texture meter, while hardness and elastic modulus were measured with a nanoindentation tester, all these tests were measured at 22%, 40%, 58% and 75% RH. Atomic force, environmental and field emission scanning electron microscopy, were used to see the films morpho-structure. The data adsorption isotherms fitted well all models tried. An increase in RH decreased the tensile strength, and increased the elongation at break of all films. The CNT addition did not affect significantly the films barrier properties (p > 0.05), but it caused an increase of about 11.36% on the elongation at break of films, at any RH higher than 40%; with no effect on the tensile strength and hardness. Films image analysis, showed a morpho-structure with high ordering, which might well correlate with CNT addition to the protein matrix. CNT were found embedded in the polymeric matrix.