Strategies and Methodologies of Improving Toughness of Starch Film

Starch films have attracted increasingly attentions since they are not only biodegradable but also edible, or using as animal feeds from the post-products. Applications of starch-based films include food packaging, coating and medicine capsules etc. One of the well-recognized weaknesses of starch-based film is brittle, especially under dry condition since starch retrogradation and instability of plasticizers. Various strategies and methodologies have been developed to improve this weakness, including plasticizing, chemical modification and physical reinforcement etc. This review includes both fundamental science such as microstructures, phase transitions and compatibility, and application techniques like processing, plasticizer evaluation and chemical modifications etc. Plasticizers act as very important role in developing starch-based materials since without plasticizer the starch-based materials will be very brittle even unprocessable. Since starches contain many hydroxyl groups all the plasticizers used for starch-based materials must contain hydroxyl or polar groups. Chemical modification like esterification and etherification can prevent starch recrystallization. Reinforcement, in particular with nano-cellulous significantly improved the mechanical properties of starch film. Based on the literatures and our experience, we have not only discussed and summarized the achievements in this area, but also pointed out the weakness of current technologies and proposed research directions in this review.