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.

Studies on the property of shape memory in thermoplastic starch (TPS) have shown good results, making such starch a suitable candidate for use in shrink packaging. It is however necessary to evaluate blending it with other bioplastics that would improve its properties while maintaining heat shrinkage. This article thus shows the evaluation of the incorporation of different concentrations of polylactic acid (PLA) and maleic anhydride (MA) as coupling agent and their effect on shrinkage and the changes in structure of the films obtained by blown film extrusion. In most of the blends, the incorporation of PLA and MA was found to favor film shrinkage, obtaining values of up to 55% due to the fact that the interaction between TPS and PLA increased with the incorporation of MA. This was corroborated by the % of MA grafted, thermogravimetric analysis (TGA), rheological and structural tests. This allowed generating a greater molecular orientation of the films, thereby obtaining greater shrinkage. It was determined that the incorporation of PLA and % MA grafted generated good shrinkage results due to the physical and chemical crosslinking achieved in the processing of the blends in the presence of MA, enhancing their application as packaging.

El desarrollo de materiales biodegradables como reemplazo de los plásticos convencionales se ha estudiado y analizado hasta su punto de producción, sin embargo, existe pocos estudios sobre la determinación del tiempo de vida útil de los pellets a partir de almidón para obtener materiales biodegradables, la mayoría se han realizado con base a pellets de madera, utilizando recubrimientos, pretratamientos térmicos, aditivos, etc., con el fin de aumentar la vida útil o tiempo en almacenamiento. En este sentido, el objetivo de este estudio se basó en determinar los efectos de las condiciones de empaque y almacenamiento sobre las propiedades finales de los pellets y las películas producidas a partir de almidón de yuca termoplástico (TPS) y ácido poliláctico (PLA). Los pellets se almacenaron en tres tipos de empaque (celulosa multicapa, polietileno y papel), tres humedades relativas (70 %, 26 % y 10 %) y se procesaron en los días 0, 8, 20, 40 y 75 para obtener las películas flexibles y realizar una medición a sus propiedades mecánicas como variable de respuesta. Se obtuvo que los factores tipo de empaque y tiempo de almacenamiento de los pellets afectan significativamente las propiedades mecánicas de tracción de las películas obtenidas a partir de los pellets almacenados, presentando una disminución del esfuerzo en el sentido longitudinal de las películas de 15 MPa a 10 MPa y un aumento del porcentaje de deformación de aproximadamente 20 % con respecto a la muestra control, debido al proceso de retrogradación y plastificación que sufre el almidón cuando es almacenado. Los empaques de celulosa multicapa y el polietileno mostraron ser dos posibles tipos de empaque para almacenar los pellets por 20 días.