Influence of Plasticizer Type on Physical and Structural Properties of Corn Starch-Based Bioplastic Films: A Comparative Study of Glycerol, Sorbitol, and Their Binary Blend

Abstract

Starch-based bioplastics represent promising alternatives to petroleum-derived packaging materials. However, the influence of plasticizer selection on corn starch film properties remains incompletely characterized, particularly for binary plasticizer systems. To evaluate the effects of glycerol, sorbitol, and their equimolar blend on the physical and structural properties of corn starch-based bioplastic films. Films were prepared via solution casting using locally extracted corn starch (5% w/v) with 10% plasticizer and acetic acid as processing aid. Physical properties (thickness, density, moisture content, water absorption, water solubility) and structural characteristics (FTIR spectroscopy) were systematically evaluated. Plasticizer type significantly influenced all measured properties. Sorbitol films exhibited highest density (1.702 g/cm³) and superior water resistance (18.09% absorption), while glycerol films demonstrated maximum flexibility but elevated water sensitivity (57.81% absorption). The glycerol-sorbitol blend showed intermediate characteristics (29.03% absorption). FTIR analysis confirmed successful plasticizer incorporation through modified O−H stretching patterns (3200–3500 cm⁻¹). Sorbitol plasticization yields films with enhanced water resistance suitable for moisture-sensitive packaging, while glycerol provides maximum flexibility for conformable applications. Binary plasticizer blends offer tunable properties for diverse packaging requirements. Locally sourced corn starch represents a viable feedstock for biodegradable packaging materials.