Starch films as an environmentally friendly packaging material: Printing performance

Starch films can be a great alternative for non-degradable conventional plastic films as packaging materials. Packaging material, besides relevant properties such as mechanical or barrier properties, should also be characterised by a good printability to provide some required information about the product. The aim of this work was to show possibility of printing of starch films. Potato starch films with 20%, 40%, 60% and 80% of glycerol as a plasticiser were obtained. The tensile strength, water vapour transition rate, and moisture content of the film were determined and compared with the literature values. Next, the surface free energy of the starch films was determined by the Owens−Wendt and van Oss–Chaudhury–Good approaches. The values of surface free energy are in the range of 59.10 to 46.10 mJ m⁻², which are higher than the surface free energy of conventional plastic films used for packaging purposes. The wettability of the obtained films was investigated by the analysis of the water droplet contact angle. The values of the water contact angle decreased when the glycerol content increased, which is related to the presence of hydroxyl groups. Finally, the films were overprinted with biodegradable printing ink and the print quality of the obtained prints was determined. The optical density of full tone areas and colour parameters were measured. The optical density increased with the increasing content of glycerol in the starch film, which is related with the wettability of the starch film. The printing performance was compared with biodegradable commercially available PLA and paper. The naked human eye control of the prints revealed that the prints on the starch-based films are poorer quality than overprinted PLA or paper samples. Despite the poorer quality of overprinted starch-based films, the results of this study show the strong potential of using starch films as a biodegradable, environmentally friendly packaging materials.