Johnsy George

Augmented properties of PVA hybrid nanocomposites containing cellulose nanocrystals and silver nanoparticles

PVA nanocomposites containing cellulose nanocrystals and silver nanoparticles have been prepared and their properties were investigated. Even though bacterial cellulose nanocrystals (BCNC) improved the mechanical properties of hydrophilic polymers like modulus and strength, they also contributed to increased brittleness. An attempt was made to reduce the brittleness of the films by incorporating Ag nanoparticles (AgNPs) along with BCNC. The AgNPs could form complexes with the hydroxyl groups of PVA and played the role of physical crosslinks, which makes them less hydrophilic and more ductile in nature. FTIR studies were used to confirm the interaction of AgNPs with PVA. The addition of AgNPs increased the elongation properties without compromising on other mechanical properties and at the same time it significantly reduced the moisture sorption also. Results of the study indicated that the combination of two different nanomaterials was highly effective in overcoming certain limitations of PVA–BCNC nanocomposites.

Hybrid HPMC nanocomposites containing bacterial cellulose nanocrystals and silver nanoparticles.

Hydroxypropyl methyl cellulose (HPMC) based hybrid nanocomposites reinforced with bacterial cellulose nanocrystals (BCNC) and silver nanoparticles (AgNPs) had been prepared and characterised. BCNC was capable of improving the tensile strength and modulus of HPMC, but they made the film more brittle. The addition of AgNPs along with BCNC, helped to regain some of the lost elongation properties without affecting other properties. Moisture sorption analysis proved that the hydrophilicity of the nanocomposite decreased considerably by the addition of these nanomaterials. Several mathematical models were also used to fit the experimental sorption results. A unique combination of two nanomaterials was highly effective in overcoming certain limitations of nanocomposites which uses only one type of nanomaterial. This type of hybrid nanocomposites with superior properties is expected to be useful in eco-friendly food packaging applications.

Synthesis and Characterization of Bacterial Cellulose Nanocrystals and their PVA Nanocomposites

Cellulose, the most widespread biopolymer, is known to occur in a wide variety of living species from the worlds of plants and microbial sources like bacteria. Bacterial cellulose produced by Gluconacetobacter xylinus in the form of long fibers can be acid hydrolyzed under controlled conditions to obtain nanocrystals. Such nanocrystals constitute a generic class of ‘green’ nanomaterial and have attained great importance in the field of polymer nanocomposites attributed to their superior properties. However, conventional sulfuric acid hydrolysis route provides cellulose nanocrystals with inferior mechanical and thermal properties. In this study, a hydrochloric acid (HCl) assisted top down approach has been adopted to synthesize bacterial cellulose nanocrystals, which is found to retain some of the natural properties of native cellulose even in nano-dimensions. The morphological parameters were analyzed using atomic force microscopy which confirmed the formation of nanocrystals. Using these novel nanocrystals, poly vinyl alcohol (PVA) nanocomposite films were prepared and characterized for elucidating their properties. The addition of nanocrystals has significantly improved the thermal stability and mechanical properties of PVA nanocomposites. Results of this study demonstrated that nanocrystals obtained by HCl have several advantages in the fabrication of high performance polymer nanocomposite films for food packaging applications.

Water Soluble Polymer-Based Nanocomposites Containing Cellulose Nanocrystals

Among the eco-friendly polymers, water soluble polymers are increasingly gaining importance to industry and academia, as they are easy to process, low cost, easily available, and more environmentally friendly than any other polymers. Water soluble polymers are widely used as stabilizers, thickeners, drug delivery materials, protective colloids, dispersants, flocculants, materials for oil recovery, etc. However, replacing nondegradable and nonrenewable plastic materials with these water soluble polymers for several applications remains as a big challenge. Several water soluble polymers, like those derived from naturally occurring proteins, polysaccharides, etc., and those obtained from synthetic methods are not having sufficient properties to replace the existing non-degradable plastic materials for most of the applications. Incorporation of nanomaterials into polymer matrices enhances the mechanical properties like tensile strength, modulus, stiffness, and impact strength significantly. Also other physical properties like barrier, optical, thermal resistance, nonflammability, etc., can also be improved by the introduction of nanomaterials. It is believed that the advances in polymer nanocomposite field will revolutionize the design, development, and performance of water soluble polymer-based materials, which ultimately have negligible adverse impact on the environment. Nanotechnology could be able to play an important role in solving this problem with the development of water soluble nanocomposite materials, which holds the key to future advances in the field of eco-friendly packaging systems. Several nanomaterials have been investigated for reinforcing water soluble polymers; however, rod-shaped cellulose nanocrystals (CNs) having high aspect ratios are found to be a promising nanomaterial for these types of applications. This chapter deals with the development and characterization of water soluble polymer-based nanocomposites containing cellulose nanocrystals and their applications.

Amine functionalised nanoclay incorporated hydroxypropyl methyl cellulose nanocomposites: synthesis and characterisation

Amine functionalised nanoclay that can be easily exfoliated in water was used in the preparation of eco-friendly polymer nanocomposite films based on hydroxypropyl methylcellulose (HPMC). These nanocomposite films were characterised using fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FESEM) analysis. Incorporation of this nanoclay helped to improve the mechanical and barrier properties of nanocomposite films. Differential scanning calorimetry (DSC) studies proved that this nanoclay has also affected the thermal properties of HPMC. These nanocomposite films proved to have better properties than conventional montmorillonite containing HPMC nanocomposites.

Water soluble polymer based hybrid nanocomposites

Hybrid nanocomposites are different from normal polymer nanocomposites, as they contain different types of nanomaterials together in a polymer matrix. These hybrids are not simply physical mixtures of different nanomaterials, but they are more homogenous and exhibit synergistic properties. Hybrid nanocomposites based on water soluble polymers can overcome several limitations of conventional water soluble polymers. Gelatin is one such water soluble protein based polymer having different applications in areas such as biomedical, food, drugs, and paper industries. Hybrid nanocomposites of gelatin nanocomposites were fabricated by incorporating three different types of nanomaterials such as cellulose nanocrystals, amine functionalized nanoclay, and silver nanoparticles in different combinations after which their properties were then evaluated. These materials were found to have good mechanical, barrier, and thermal properties. This chapter is intended to give an insight about the synthesis, characterization, and applications of gelatin-based hybrid nanocomposites.