Thermoplastic starch (TPS) offers an alternative to petrochemical-based plastics because as well as being a final product in itself, TPS can be used as a precursor for the production of new materials. In addition to high temperature and shear, the presence of plasticizers is essential in the TPS production process, to break the strong inter-and intra-molecular interactions of the starch chains. The properties of these plasticizers-their functional groups, molecular weight, thermal stability, and compatibility with the polymer, among others-play an important role in the production of TPS. This work therefore brings together research evaluating starch-plasticizer molecular interactions and their effect on the structure, polymer properties, retrogradation, and processing of TPS obtained by extrusion; in addition, it collects and analyzes information on the process conditions used in the extrusion of different starches in the presence of different plasticizers. The objective of this review is to provide a clear description of the importance of the effect of plasticizers on the properties of TPS obtained by extrusion, indicating the potential of some plasticizers to broaden the field of application of TPS.

Thermoplastic starch (TPS) has emerged as an essential alternative to produce environmentally friendly packaging; however, retrogradation is a disadvantage that affects its shelf life. This study analyzed the co-plasticizing effect of isosorbide on the mechanical, thermal, physicochemical, and microstructural properties and the retrogradation of films obtained by blown film extrusion from thermoplasticized starch with mixtures of glycerol and isosorbide in different ratios (3:0, 2:1, 1:2, and 0:3, respectively). The results showed that the higher concentration of isosorbide significantly increased the tensile strength; however, it reduced the elongation. Retrogradation modeled using the Avrami equation showed that the presence of isosorbide reduced the retrogradation rate (k) and modified the recrystallization mechanism (n). The relative crystallinity in the plasticized TPS films was reduced to 89%, and the adsorption significantly decreased. Isosorbide was very important in reducing the retrogradation of TPS. The best performance was obtained with the 2:1 ratio of glycerol/isosorbide due to the synergistic effect between the plasticizers. The results would allow tuning the properties of TPS films by combining glycerol/isosorbide in different ratios, which enables the design of materials tailored to potential application requirements.