Preparation of cassava starch/montmorillonite nanocomposite film

Abstract

Cassava starch/montmorillonite nanocomposite films were prepared by solution casting technique. This research was focused on the exploitation of an intercalating agent (cationized diethanolamine) to delaminate the layered silicate of montmorillonite in order to homogeneously disperse the nanoparticles in starch matrix. Mixture of cassava starch, montmorillonite (MMT), diethanolamine (DEA) (calculated from the optimum cation exchange capacity of MMT:DEA of 2:1), glycerol as a plasticizer, and distilled water adjusted to pH 7.0 was well mixed with a homogenizer and heated to gelatinize temperature of 70-80 ํC. The obtained homogeneous starch solution was cast onto acrylic mold and allowed to dry in open air. The dried film was peeled off and subjected to property investigation and characterizations.The results showed that change in the montmorillonite structure from layered platelets to individually delaminated sheet was characterized by X-ray diffraction (XRD). The starch/montmorillonite nanocomposite film exhibited the complete disappearance of XRD reflection at 2 theta = 5.590 ํ, indicating the nanoscale dispersion of montmorillonite. Transmission electron microscopy (TEM) results further supported the blend composite occurring at the nanoscale level. Even though the nanocomposite between starch and montmorillonite was achieved but tensile strength and Young's modulus were found to be opposite to an expectation due to plasticization effect of DEA. This also significantly increased the percent elongation at break. Furthermore, due to the strongly hygroscopic nature of DEA, it led to subsequent disappointment that other physical properties such as water vapor transmission rate (WVTR), and moisture absorption were increased which were not desirable properties for packaging films.