High efficiency plasticizers for flexible thermoplastic zein processed by extrusion and injection molding

This study addresses the limited availability of injection-molded zein systems by evaluating three structurally contrasted plasticizers, diethylene glycol (DEG), dipropylene glycol (DPG), and diethanolamine (DEA), to produce thermoplastic zein by hot extrusion and injection molding. Beyond demonstrating melt processability, the work seeks to clarify how plasticizer chemistry governs the structure-property relationships of zein under scalable thermoplastic processing conditions. All formulations yielded homogeneous injection-molded specimens. FTIR and XRD revealed plasticizer-dependent perturbations in the protein matrix, while DSC and DMTA showed clear differences in thermomechanical softening. The linear and flexible structure of DEG promoted the strongest disruption/reorganization of zein packing, increasing molecular mobility and translating into the lowest glass transition temperature (T g ) (42.0 ºC for 25 DEG), highest ductility (elongations at break: 74.2%) and highest impact strength (∼70 kJ m −2 ). In contrast, the branched structure of DPG and the amino-diol character of DEA produced more moderate plasticization, retaining higher stiffness and T g values, while DEA strongly increased surface wettability (WCA< 10º). Bulk water uptake reached high maxima (∼277–310% at 7 days). Under controlled composting, near-complete disintegration occurred within 4–6 weeks (20DPG slowest). Overall, plasticizer chemistry enables the injection molding of tunable zein parts with short composting disintegration times.