GLYCEROL DERIVATIVES AS A MODERN PLASTICIZERS FOR STARCH FILMS

Due ecological reasons there is a considerable interest in biodegradable films made from renewable and natural polymers, such as starch. Starch films are not meant to totally replace conventional packaging polymer films, but they might be a competition in several application, where traditional packaging cannot function. Moreover, starch as a raw material exhibit many benefits, such as relatively low price, abundant, biodegradable, and edible. Films prepared from starches are isotropic, odourless, tasteless, colourless, non-toxic and biodegradable. Finally, they are nutritious and safe, so they are used in the marketing of food. Unfortunately, the starch films present poor tensile properties and sensitivity to moisture content. In order to modify starch films properties the addition of various plasticizers is used. Commonly as a plasticizer water and glycerine is used. In this work, we use glycerol derivatives as a modern plasticizers for starch films obtained from potato starch by the tape casting technique, which allows to obtained films with constant thickness and 20 cm length. The influence of the ratio of various plasticizers: glycerol, pentaerythiolethoxylate, glycerol ethoxylate and Poligliceryn-3 on the mechanical properties and surface free energy was investigated. The plasticizers selected by us are characterized by a large number of functional hydroxyl groups. The starch films with the mixture of plasticisers reveal better usable properties and higher mechanical properties than with only one plasticizer. However, glycerol derivatives they cannot be used without the addition of glycerol. Furthermore, surface free energy was determinate by OwensWendt and van Oss-Chaudhury-Good method. The values of SFE are in the range 50–60 mJ/m2 and higher than values of typical plastic films, which are used in packaging industry. Obtained starch films are characterized by quite high polar component of SFE, with may be related with the influence of hydroxyl groups. Our results support the use of glycerol derivatives as modern plasticizers for biodegradable films and may open up new possibilities for applications of these compounds.