Compatibilization of starch-zein melt processed blends by an ionic liquid used as plasticizer.

An ionic liquid (1-butyl-3-methyl imidazolium chloride [BMIM]Cl) was used as a plasticizer in starch, zein and their blends; and compared to glycerol, a classical plasticizer of starch. Thermoplastic plasticized biopolymer materials were obtained by melt processing using a twin screw microcompounder. Such a device allows simulating a twin screw extrusion process on small batches of a few grams, and to evaluate the necessary specific mechanical energy input for native starch destructurization; and the final apparent melt viscosity. Both were shown to be significantly reduced for starch in presence of [BMIM]Cl (compared to glycerol), while zein processing behavior was less sensitive to the plasticizer used. This induces significant starch/zein viscosity ratio differences, which affect melt mixing of the starch zein blends. In starch rich blends, this results in smaller zein aggregates in the case of [BMIM]Cl. The characterization of the materials indicates that, compared to glycerol, the use of [BMIM]Cl leads to less hygroscopicity, a more efficient plasticization of both starch and zein phases and a compatibilization of starch/zein blends.