Development and characterization of natural gum base Nanocomposite

Abstract

Natural gum based bionanocomposite film using babul gum obtained from Vachellia nilotica .L and cellulose nanofibrils (CNF) extracted from bamboo culms via steam explosion cum acid treatment was developed for biomedical and packaging applications. Alkali treatment (using NaOH) followed by bleaching (using sodium hypochlorite) of chopped bamboo culms resulted in removal of impurities like pectin, lignin, hemicellulose and other organic compounds. Steam coupled acid treatment of the bleached cellulose pulp resulted in the depolymerization and defibrillation of the fibres to produce cellulose nanofibrils. The structural, morphological, chemical, and thermal properties of CNF were analysed using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). TEM and SEM images showed that the CNF was composed of network like structure of long fibrils of nanocellulose having the size of few micrometres in length and 50-60 nm in width. The CNF had a crystallinity of 54.46% which was greater than that of the raw bamboo fibre (41%). The chemical composition of the raw fibre and the CNF was analysed by FT-IR micrographs. TGA showed that the CNF was thermally more stable than the raw fibre and the results of peak temperature of 10 and 20% weight loss of raw fibre and CNF substantiated the same. The effect of CNF content (1, 3, 5, and 10 wt% based on gum) on the thermal, mechanical, water solubility, contact angle, and moisture content of nanocomposites was studied. Properties of babul gum film such as mechanical properties were improved significantly (p<0.05) by combining with CNF. The TGA analysis revealed that the composites had more thermal stability than the pristine gum film. The tensile and elastic modulus of composites increased significantly (p<0.05) when the concentration of the CNF increased in the gum matrix, while the elastic property decreased with the addition of CNF. The contact angle was found to be increasing with increasing the concentration of CNF added to the gum 64

matrix resulting in less hydrophilic composite with high CNF content. The moisture content tested for the composite films showed no significant difference with the addition of CNF. Water solubility tested showed around 90-95% of the film was dissolved completely in water. The CNF obtained from bamboo fibre can be used as reinforcing agent for the preparation of bio-nanocomposites and they can have a high potential for the development of completely biodegradable edible films which can be used for biomedical applications and packaging.