The Effects of Novel Additives Used in PVA/Starch Biohybrid Films

The main aim of this chapter is to indicate the importance of additives and modifications used for PVA/starch biohybrid films. The additives and modifications used to improve the mechanical, thermal, and morphological properties of films are plasticizers, cross-linkers, fillers, physical and chemical treatment, and natural materials as well as thermoplastic starch. Plasticizers are preferred for higher molecular dynamism because of flexibility of functional groups in PVA and starch. Their flexibility is considerably affected by carboxyl and hydroxyl groups of plasticizers. The use of cofunctional groups increases the plasticity, flexibility, and physicochemical and mechanical properties of films. Moreover, cross-linking modifications are also effective to enhance the properties of biofilms. These modifications improve the tensile strength, modulus of elasticity, water resistance, thermal resistance, swelling behavior, and antibacterial activity of films. Fillers are also used to enhance the properties of PVA/starch films. In this way, the properties such as gas barrier, mechanical stiffness, transparency and thermal stability of the filler-added films are improved. The chemical and physical modifications provide stronger hydrogen bonds in films due to increasing carboxyl groups. Thus, the physical, biological, and chemical properties of films are improved because of the changing molecular structure via esterification, etherification, hydrogen bonding, and oxidation. etherification, hydrogen bonding, and oxidation in their molecular structure.