Facile Fabrication of Chitosan/Starch Composite Films with Fumed Silica as an Additive

Chitosan/cassava starch (CS/ST) composite films with different CS:ST (w/w) ratios were prepared by solution casting and investigated as a support for fumed silica (fSiO2) dispersion. The CS, as a 1% (w/v) solution in 1% (w/v) acetic acid, and gelatinized ST, as a 3% (w/v) solution in 1% (w/v) acetic acid, were mixed at the appropriate volume ratios with a homogenizer, and then fSiO2 at 1, 3, or 5% (w/w of CS) was added and cast as films. The morphology, tensile strength, contact angle, X-ray diffraction (XRD) pattern, and surface functional groups of the films were investigated. The external morphology of the CS/ST composite film revealed that the fSiO2 particles were homogeneously dispersed into the polymer matrix. The water absorption and surface hydrophobicity of the composite film increased with increasing ST or CS contents. The hydrophobic acetyl groups of CS caused a notable reduction in the wettability as well as the water adsorption ability, which are preferable for a packaging film application. The CS/ST film with a high fSiO2 content had a higher tensile strength due to the reinforcement effect of the fSiO2 nanoparticles. The XRD patterns of the CS/ST films revealed that the 2 of the crystalline region of CS were slightly changed when including the fSiO2. The shift in the ST diffraction peak was probably due to the change in its chain orientation caused by hydrogen-bonding interactions between CS and ST molecules, resulting in their good adhesion.