The Mechanical and Water Barrier Properties of Cassava Starch/Citric Acid Incorporated with Palm Oil

Abstract

Starch-based bioplastic is susceptible to degradation due to water absorption. The addition of citric acid and palm oil may improve the mechanical and water permeability of bioplastic films produced with cassava starch. In this study, four bioplastic films were prepared with different concentrations of citric acid (5% and 10% w/w) and palm oil (2% and 4% w/w) using the solution casting method and glycerol as the plasticizer. To determine the influence of citric acid and palm oil on the films, physical (i.e., thickness, tensile strength, elongation at break, moisture absorption, moisture content, water vapor permeability, and water contact angle) and chemical analyses (i.e., thermogravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy) were measured. Bioplastic film containing 5% citric acid and 2% palm oil (Sample E) has the highest tensile strength (1.60 MPa) and the lowest water vapor permeability (1.16±0.02% w/w). The analyses of differential scanning calorimetry and Fourier transform infrared spectroscopy have confirmed that the enhanced mechanical properties were due to the formation of crosslinks. Moreover, crosslinks may have increased the bulkiness and the water contact angle. The addition of palm oil further increased the water contact angle to enhance the resistance of cassava starch film against moisture absorption and water vapor permeability.