Effect of the preparation method on the properties of nanocomposites based on chitosan, montmorillonite and essential oils

The aim of this study was to know if the addition order of the components in the film forming solution can modify the characteristics of the final film in order to obtain films with improved physical properties intended for packaging applications. Chitosan films (CH) at 1% were elaborated with montmorillonite (MMT) at 10%, essential oils (cinnamon CEO, and thyme TEO) at 1.5% and glycerol. Two methodologies were used: adding MMT at the beginning (M1) or at the end (M2) of the film preparation method. Water vapor permeability (WVP), mechanical properties, solubility (S), x-ray diffraction (XRD), FTIR and contact angle were evaluated. The combined effects of MMT and CEO using M1 produced films with lower WVP and higher tensile strength compared with M2, probably because MMT in M1 had more time in contact with CH than in M2. Also, SEM display a more compact structure in films using M1 with CEO. X-ray diffraction show that films with M1 were exfoliated while with M2 had an intercalated structure. Therefore, CH films with CEO prepared following the M1 process had better properties than those obtained by method 2.