Plasticized Starch/Gelatin Blends with Humidity-Activated Shape-Memory Behavior

Biodegradable and bio-based polymers, such as starch and gelatin, are emerging as an important alternative to the use of conventional polymers. In this work, different proportions (1/1, 1/1.5, 1/2, and 1/2.5) of these bio-based polymers will be investigated, with the primary objective of considering their strong moisture dependence as an advantage instead of a problem, as commonly considered. For this interesting challenge, the humidity-activated shape memory effect has been studied in both neat and plasticized starch. Additionally, for the first time, to the best of our knowledge, the shape-memory behavior activated by humidity in gelatin, as well as in starch/gelatin blends, is reported. In all cases, starch, gelatin, and their plasticized blends show excellent values in terms of strain fixity ratio, obtaining values of about 100% in all cases, and strain recovery ratio, with values higher than 90% for the samples studied. Moreover, considering their potential application as food packaging, mechanical response, wettability, water permeability, water uptake rate, and roughness is also studied in this work, taking into account the effect of the different amounts of gelatin on the final behavior of the materials.