Fabrication and characterization of carboxylated cellulose nanocrystals reinforced glutenin nanocomposite

Abstract

The non-biodegradable and non-renewable nature of plastic packaging has led to increasing interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanofillers). One such material is wheat gluten and its components. In this study we investigated nanocomposite materials prepared by casting a mixture of extracted glutenin from wheat gluten as the matrix and different concentrations of 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-carboxylated cellulose nanocrystals (C-CNC) as the reinforcing agent. The resulting films were characterized for their thermomechanical and barrier properties. Scanning electron microscopy (SEM) observations confirmed that the filler was homogeneously distributed in the matrix at the low and medium loadings, but some agglomerates and voids were visible at concentrations > 5 wt%. The mechanical properties showed that the presence of C-CNC (5 wt%) resulted in an increase (58.8 %) in tensile strength (TS) of glutenin films while at higher contents, the TS tended to decrease because of partial agglomeration of the filler. These effects were also reflected in the dynamic mechanical analysis (DMA) results and at a 5 wt% loading of nanocrystals the glutenin film gave the highest storage modulus (E′). The results obtained from differential scanning calorimetry (DSC) curves indicated that increasing the amount of C-CNC from 0 to 10 wt% led to an increase in glass transition temperature (Tg) from −29.8 to −23.7 °C. Although the use of C-CNC reduced the resistance to water vapor permeability (WVP) and water absorbance (WA), its incorporation up to 5 wt% resulted in composites with the lowest weight loss in water (WL). These results demonstrated that nanocellulose can reinforce glutenin polymers and that this system has potential as a packaging material, although much further study is needed.