Development and characterization of ductile polylactic acid blends with plasticized zein for injection molding applications
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This study explores the development of polylactic acid (PLA) blends incorporating plasticized zein, a corn-derived protein, and dipropylene glycol (DPG) as a biobased plasticizer to enhance compatibility and processability. Blends were produced via twin-screw extrusion and injection molding, with plasticized zein content ranging from 10 to 50 wt%. Mechanical testing showed a significant increase in ductility, with elongation at break rising from 6.3% (neat PLA) to 56.3% (50 wt% zein), accompanied by reduced tensile strength (58.4 MPa to 22.7 MPa) and impact resistance (42.2 kJ/m 2 to 11.5 kJ/m 2 ), due to phase separation and limited compatibility. Shore D hardness slightly declined (from 82.9 to 77.4). Thermal analysis revealed a single glass transition temperature (T g ) in all blends, indicating partial miscibility, with T g decreasing from 59.5°C to 39.9°C as zein content increased. Thermogravimetric analysis showed reduced thermal stability with zein addition, dropping the initial degradation temperature from 360.0°C to 188.2°C. Morphological analysis indicated greater heterogeneity at higher zein levels due to partial miscibility. Colorimetric data showed visible changes, and FTIR spectra confirmed physical interactions and partial miscibility between PLA and zein.
