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

摘要

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 tactoieds 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.