Isosorbide, a green plasticizer for thermoplastic starch that does not retrogradate

• Isosorbide is an innovative renewable solid plasticizer for thermoplastic starch.
• Crystallinity and mechanical properties do not change in the course of time.
• Thermoplastic starch plasticized with isosorbide is not subjected to retrogradation.
• Thermoplastic starch plasticized is less sensitive to water uptake that glycerol one.

Isosorbide is a non-toxic biodegradable diol derived from bio-based feedstock. It can be used for preparing thermoplastic starch through a semi-industrial process of extrusion. Isosorbide allows some technological advantages with respect to classical plasticizers: namely, direct mixing with starch, energy savings for the low processing temperature required and lower water uptake. Indeed, maize starch was directly mixed with the solid plasticizer and direct fed in the main hopper of a co-rotating twin screw extruder. Starch plasticization was assessed by X-ray diffraction (XRD) and dynamic-mechanical analysis (DMTA). Oxygen permeability, water uptake and mechanical properties were measured at different relative humidity (R.H.) values. These three properties turned out to be highly depending on the R.H. No retrogradation and changing of the material properties were occurred from XRD and DMTA after 9 months.