G. Siva Mohan Reddy

Structure and properties of poly (lactic acid)/Sterculia urens uniaxial fabric biocomposites

Uniaxial cellulose fabric Sterculia urens reinforced poly (lactic acid) (PLA) matrix biocomposites were prepared by a two-roll mill. In order to assess the suitability of Sterculia fabric as reinforcement for PLA matrix, the PLA/Sterculia fabric biocomposites were prepared. Tensile parameters, such as maximum stress, Youngs modulus and elongation-at-break, were determined using the Universal Testing Machine. The effect of alkali treatment and silane-coupling agent on the tensile properties of PLA-based biocomposites was studied. The results of thermogravimetric analysis show that uniaxial treatment of the fabric can improve the degradation temperature of the biocomposites. Moreover, morphological studies by scanning electron microscopy confirmed that better adhesion between the uniaxial fabric and the matrix was achieved. It was established that standard PLA resins are suitable for the manufacture of S. urens uniaxial fabric reinforced biocomposites with excellent engineering properties, useful for food packaging.

Structure and properties of highly toughened biodegradable polylactide/ZnO biocomposite films

Zinc oxide (ZnO) powder was investigated in terms of its use as filler in order to improve the inherent properties of PLA. Biocomposite films of PLA with different loadings of ZnO were prepared by solution casting method. Morphological analyses using SEM and POM showed that the ZnO particles were well dispersed at low ZnO loading, with starfish-like morphology. However, ZnO agglomeration was found at higher ZnO loadings. Tensile testing showed improvements in strength and a moderate improvement in toughness at 2 wt% ZnO loading. This is consistent with the homogeneous dispersion of ZnO particles in the PLA matrix. ZnO particles incorporation improved the thermal stability of PLA. In summary, ZnO particles were shown to have the potential as a toughener in the preparation of biocomposites with better integrity, although other approaches, such as the use of compatibilizer in the surface modification of ZnO will be needed for the concurrent improvement of PLA properties.

Development of microbial resistant Carbopol nanocomposite hydrogels via a green process

The present scientific research resulted in the development of novel microbial resistant inorganic nanocomposite hydrogels, which can be used as antibacterial agents. They are promising candidates for advanced antimicrobial applications in the field of biomedical science. Novel inorganic nanocomposite hydrogels were developed from Carbopol® 980 NF and acrylamide. Dual-metallic (Ag0-Au0) nanoparticles were prepared (via a green process) by the nucleation of silver and gold salts with mint leaf extract to form a hydrogel network. The Carbopol nanocomposite hydrogels contain (Ag0-Au0) nanoparticles ∼5 ± 3 nm in size, which was confirmed by transmission electron microscopy. The developed hydrogels were characterized using Fourier transform infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The pure and inorganic nanocomposite hydrogels developed were tested against Bacillus and E. coli, for their antibacterial properties. The results indicate that the inorganic nanocomposites show significantly greater antimicrobial activity than the pure hydrogels. Therefore, novel microbial resistant Carbopol nanocomposite hydrogels can be used as potential candidates for antibacterial applications.

Development and characterization of nano-multifunctional materials for advanced applications

Multifunctional zinc oxide–bismuth ferrite and tin dioxide–bismuth ferrite have been synthesized using a double precipitation technique. The structural formation, chemical composition, morphology and thermal properties were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy with energy dispersive spectroscopy and transmission electron microscopy. Temperature-dependent magnetic behaviour of zinc oxide–bismuth ferrite and tin dioxide–bismuth ferrite were studied using a vibrating sample magnetometer in the range of 5 K to 300 K. The results indicate that zinc oxide–bismuth ferrite is a potential candidate for spintronics applications.

Mechanical properties of uniaxial natural fabric Grewia tilifolia reinforced epoxy based composites: Effects of chemical treatment

The effects of chemical treatment on the mechanical, morphological, and chemical resistance properties of uniaxial natural fabrics, Grewia tilifolia/epoxy composites, were studied. In order to enhance the interfacial bonding between the epoxy matrix and the Grewia tilifolia fabrics, two different types of treatment: alkali treatment (5 % NaOH) and (3-aminopropyl)-triethoxysilane coupling agent (CA), were used. The epoxy composites containing 0–15 wt% of Grewia tilifolia fabric were prepared by hand lay-up technique, at room temperature. The tensile and flexural properties of the untreated, alkali-treated and coupling agent treated Grewia tilifolia reinforced epoxy composites were determined as a function of fabric loading. The 9 % wt Grewia tilifolia fabric reinforced epoxy composites showed improved tensile and flexural modulii when compared to the neat epoxy matrix. Significant improvement in the mechanical properties was obtained when both alkali and coupling agent treated fabrics were used as reinforcement. Morphological studies demonstrated that better adhesion between the fabrics and the matrix was achieved especially when the alkali-treated and coupling agent treated Grewia tilifolia fabrics were used in the composites. For the water absorption and chemical resistance studies, various solvents, acids and alkalis were used on the epoxy composites. This study has shown that Grewia tilifolia fabric/epoxy composites are promising candidates for structural applications, where high strength and stiffness are required.

RETRACTED: Influence of alkali metal cations on the thermal, mechanical and morphological properties of rectorite/chitosan bio-nanocomposite films

The main theme of this work is to study the influence of ion-exchangeable alkali metal cations, such as: Li(+), Na(+), K(+), and Cs(+) on the thermal, mechanical and morphological properties. In this regard, a set of rectorite/chitosan (REC-CS) bio-nanocomposite films (BNCFs) was prepared by facile reaction of chitosan with ion-exchanged REC clay. The microstructure and morphology of BNCFs were investigated with XRD, TEM, SEM and AFM. Thermal and tensile properties of BNCFs were also investigated. As revealed from TEM and XRD results, the BNCFs featured a mixed morphology. Some intercalated clay sheets, together with nano-sized clay tactoids were obtained in LiREC/CS, NaREC/CS and KREC/CS of the BNCFs. From fractured surface study, via SEM, it was observed that the dispersion of chitosan polymer attaches to (and covers) the clay platelets. FTIR confirmed strong hydrogen bonds between clay and chitosan polymer. In addition, the thermal stabilities significantly varied when alkali metal cations varied from Li(+) to Cs(+). The BNCFs featured high tensile strengths (up to 84 MPa) and tensile moduli (up to 45 GPa). After evaluating these properties of BNCFs, we came to conclusion that these bio-nano composites can be used for packaging applications.

Significances of Nanostructured Hydrogels for Valuable Applications

Nanostructured hydrogels represent a unique class of materials that synergizes the advantageous features of hydrogels. Research into nanostructured hydrogels for biomedical applications has seen great progress in recent years owing to their unlimited potential to advance human health. The development of nanotechnology provides opportunities to characterize, manipulate, and organize matter systematically at the nanometer scale. This is because nanostructured systems in general and nanostructured polymer hydrogels in particular have noble advantages as transporters for a wide range of drugs and tissue engineering scaffolds for biomedical (therapeutic) applications. This chapter explains the design and development of different nanostructured hydrogels and their applications in the biomedical field.

Application of cross-linked soy protein isolate with resorcinol films for release studies of naturally occurring bioactive agent with antiproliferative activity

The potential of soy protein isolate films as a release system for naturally occurring antiproliferative agent was investigated. The soy protein isolates was cross linked with resorcinol and the resorcinol content was varied between 10-30 %. The release study was monitored over a period of 24 h at a pH of 7.4. Different kinetic release models were used to determine the mechanism of release of bioactive agent from the films. The release profiles of the SPI films of selected degree of cross-linking were anomalous (non-Fickian) and case II transport, with n values in the range of 0.97-1.01. The degree of cross-linking provided an effective means of regulating the release rate of the SPI films, and hence potential for use as drug release system. These films were further characterized by Fourier transform spectroscopy (FTIR), spectroscopy, scanning electron microscope (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) which confirmed the successful incorporation of curcumin onto the films.

Hydrophobic/Hydrophilic Nanostructured Polymer Blends

It is the objective of this chapter to review the hydrophobically modified water-soluble and other hydrophilic nanostructured polymer systems and their biocompatibility for potential use in biomedical applications. The nanostructured polymer systems reviewed include block copolymers, amphilic copolymers, nanostructured polymer blends, and networks that exhibit hydrophilic/hydrophobic micro-/nanophase domain structures. Enhanced biocompatibility and mechanical strength appear to be a general characteristic of such systems as compared to single phase hydrophilic polymers. Fabrication of solid surfaces in terms of chemical affinity including hydrophilicity is a technology of importance in the development of various devices and functional materials. In particular, super-hydrophobic/super-hydrophilic patterning is crucial because it is applicable to the control of liquid flow and the immobilization of functional materials into specific areas. The ability to create superhydrophilic-superhydrophobic micro patterns and arrays on nanostructured polymer blends is essential for a variety of applications ranging from micro fluidics to cell microarrays. Despite a lot of research done on the development of new superhydrophobic and superhydrophilic surfaces on nanostructured polymer blend films, creating precise, and stable micro patterns of superhydrophilic and superhydrophobic areas has proved challenging. To the best of our knowledge, most of the existing methods are based on the surface modification of a rough superhydrophobic and or superhydrophilic substrate through a mask to reverse hydrophobicity of the exposed areas.

Side Chain Liquid Crystalline Polymers: Advances and Applications

Liquid crystalline polymers (LCPs) are a class of polymers that show liquid crystal phase, they show both anisotropic properties which originate from mesogenic units and good mechanical properties which come from long-chain structures. Since the 1960s, LCPs have aroused considerable attention because of their wide applications as engineering plastics, high-strength and high-modulus fibers, electro-optic or nonlinear optic materials, stationary phases and their use as gas separation membranes, etc. On the basis of the manner in which the mesogenic units are incorporated into the polymers, LCPs are classified as main chain liquid crystalline polymers (MCLCPs) in which the mesogenic units are connected in the backbone, or side chain liquid crystalline polymers (SCLCPs) in which the mesogenic units are attached to the backbone as side pendants.