a b s t r a c t
Bioplastics made from renewable and biodegradable polymers are considered as promising materials for
relevant industrial applications in agriculture, packaging, pharmacy, etc. Their added value would arise
from their hydrophilic character and ability controlling the release of “active agents”. On these grounds,
this work deals with the development of protein-based bioplastics to be used as water resources (with
improved water uptake) and able to control the release of an agricultural nutrient (KCl), both of them
required for the suitable plant growth. Their thermo-mechanical and physico-chemical properties were
determined through dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry
(DSC), water absorption and diffusion tests. The use of less hygroscopic plasticizers, in the new formulations
proposed, has modified bioplastic release/swelling properties. Among the modifiers studied,
citric acid achieved the most suitable balance between an enhanced protein/salt affinity and the material
mechanical properties, yielding slow release patterns, higher KCl leaching capacity and suitable water uptake.