Green nanocomposite films based on cellulose acetate and biopolymer-modified nanoclays: studies on morphology and properties

Abstract

Green nanocomposite films were elaborated from cellulose acetate (CA), three clay types as nanofillers, namely natural montmorillonite (Na-MMT) and organo-modified MMT with gelatin (Ge-MMT) or chitosan (Cs-MMT) and in the presence or absence of triethyl citrate (TEC) as an eco-friendly plasticizer, using solvent-casting method. The formation of the organoclays was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The nanoclay dispersion within CA matrix was investigated by XRD analysis together with transmission electron microscopy (TEM). For unplasticized nano-hybrids, it was observed intercalated/exfoliated structures with a small clay tactoids remaining, although a more aggregated structure was obtained in the presence of unmodified MMT. The plasticized nano-hybrids exhibited mainly intercalated/aggregated structure, while some exfoliated layers were much labeled in the presence of Ge-MMT nanoclay. Glass transition (T g) and melting (T m) temperatures of CA, as attested by differential scanning calorimetry (DSC) analysis, were slightly affected by clay addition. Besides, the thermal stabilities and water vapor barriers properties of CA-based nano-hybrids were enhanced by increasing clay loading, while the optical clarity, assessed by UV–visible spectroscopy, was rather decreased. Better nanocomposite properties were reached in the presence of Ge-MMT at 5 wt%. The clay impact on CA biodegradation was also studied by gravimetric, scanning electron microscopy (SEM) and TGA methods. The results highlighted a retarding effect of nanoclays, except for Ge-MMT that showed a catalytic role.