Synergistic Effect of Citric Acid and Poly(vinyl alcohol) for Film Applications

Polyvinyl alcohol (PVOH) is newly profound substitute as food packaging material owing to its excellent physio-chemical properties. However, PVOH has poor water resistance properties due to its highly hydrophilic nature, rendering it soluble in water. Therefore, potential crosslinking agent, citric acid (CA) was introduced to develop CA crosslinked PVOH films. This study reports the application of different concentrations of CA as crosslinking agent on the tensile properties, Fourier Transform Infrared Spectroscopy (FTIR) analysis and solubility of CA-PVOH film. CA-PVOH films were formulated at different proportions of CA (0, 2, 4, 6, 8 and 10 wt.%) and produced by using a 100 μm coating bar on a release paper. The study showed that the increase in CA content significantly decreases the solubility of the films. Formation of ester bonds in PVOH matrix when incorporating with CA, increases the interlinkage between the molecules and limiting the hydroxyl groups of PVOH bonding with water. For FTIR spectrometry, the C=O stretching caused by carboxyl group in CA and ester bond increases as the CA content increases. The ultimate tensile strength and Young’s Modulus significantly increased as the CA content increases, where the maximum tensile strength and Young’s Modulus achieved at 10.26 MPa and 17.01 MPa respectively for 6 wt.% CA was incorporated into PVOH. The elongation at break for 6 wt.% is 34.3%. 6 wt.% is found to be the optimum dosage of CA that should be incorporated into PVOH as it exhibits lower film solubility, higher tensile strength, higher Young’s Modulus and low ductility.