Search

Cellulose nanofibre isolated from renewable resources is a potential reinforcing filler for elastomeric products. However, the key issue lies in terms of incompatibility between the polar fibre and the non-polar matrix which can lead to fibre agglomeration in the composite. In the present study, the effect of maleic anhydride-g-natural rubber (MA-g-NR) compatibiliser on the mechanical, rheological and thermal properties of Natural rubber/cellulose nanofibre (CNF) composites were evaluated. MA-g-NR was prepared by grafting maleic anhydride on to NR via melt-mixing process. The nanocomposites with 4 phr of MA-g-NR (NCM4) exhibited significant enhancement by 57% in tensile strength, 23% in tensile modulus and 19% in tear strength compared to NR gum vulcanizate. The SEM images of tensile fractured surfaces and RPA studies revealed improved rubber-fibre interaction for compatibilized composites. The thermal stability of the composite was not affected by the addition of a natural fibre (CNF) and MA-g-NR.

Multiwalled carbon nanotubes decorated with nanosilica particles (CS hybrids) were prepared for the first time by ultrasonication assisted mixing of the aqueous dispersions of carboxylated multiwalled carbon nanotubes (MWCNTRs) and colloidal nanosilica. The natural rubber (NR) nanocomposite (NRCSF) was prepared with CS hybrid filler by latex stage mixing method. The SEM and TEM images and strain sweep studies confirmed the formation of segregated network structure inside the nanocomposite due to the alignment of hybrid fillers along the periphery of NR latex spheres. The NRCSF composite exhibited excellent mechanical properties and solvent barrier properties. The NRCSF composites displayed high dielectric constant and low electrical percolation threshold (0.80 vol%). The composite exhibited low dielectric loss because of the presence of insulating nanosilica particles around conducting carbon nanotubes. These elastomeric nanocomposites with high k and low loss are promising in the field of dielectric elastomers for actuator applications.

Natural Rubber (NR) composites containing segregated network structure of Multiwalled carbon nanotubes (MWCNT) were prepared by ultrasonication assisted latex stage mixing technique. The preparation involved acidic treatment of the nanotubes prior to ultrasonication in order to get carboxylated MWCNTs (MWCNTR). The final composites contained segregated network of carbon nanotubes. The presence of segregated structure was confirmed by Transmission electron microscopy (TEM). The NR-MWCNTR composites prepared exhibited excellent mechanical and gas barrier properties with improved solvent resistance and cross-link density at very low concentration of nanotubes which can be attributed to the segregated network present in the composites. The cellular structure and occluded rubber due to the confinement of rubber within the networks in the NR-MWCNTR composite provided tremendous reinforcement. The Thermogravimetric analysis (TGA) showed that the added nanotubes did not alter the thermal stability of the composites

The urge for materials with diverse applications has paved the way to fabricate composites based on, one-dimensional filler like nanoclays. The main aim of the work was to study the effect of mill mixing and latex stage mixing on the reinforcing effect of organoclay in Nitrile Rubber. The non-ionic surfactant assisted latex stage mixing route proved to be more efficient and feasible when compared to mill mixing. Mechanical properties were measured and, about 150% increase in tensile strength and 79% increase in tensile modulus were obtained for the latex based composites at 3 phr clay loading when compared to neat rubber composites. Dynamic strain sweep tests revealed that, the low strain modulus for latex mixed composites was higher. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) results indicated that the addition of organoclay hardly affected the thermal properties of the rubber matrix. Transmission Electron Micrographs revealed homogeneous dispersion of partially exfoliated and intercalated nanoclay platelets in the latex state substantiating the viability of latex mixing over mill mixing. The extent of reinforcement in the nanocomposites was also analyzed with the help of different micromechanical models.

In the present study Vulcastab VL (polyethylene oxide condensate) has been used as a non-ionic surfactant to get stable aqueous dispersions of multiwalled carbon nanotubes (MWCNTs). Sonication time and surfactant concentration were optimised by UV-vis spectroscopy and dynamic light scattering technique. Homogeneously dispersed surfactant coated individual MWCNTs in water were clearly evident from Transmission electron microscopy (TEM). Natural rubber –Multiwalled carbon nanotube (NR-MWCNT) nanocomposites were prepared by latex stage mixing. Instead of being randomly dispersed, MWCNTs were found to retain at the boundary of rubber particles resulting in a segregated network as evidenced from TEM. Addition of very small amount of MWCNT showed remarkable improvement in mechanical, thermal, electrical and barrier properties of NR. Segregated network of CNTs resulted in very low electrical percolation threshold (0.043 vol%) for the composite with enhanced dielectric properties.

The catalytic activity of a low priced and non-toxic catalyst (sodium carbonate) was explored in an aminolytic degradation reaction of polyethylene terephthalate (PET) bottle waste with hydrazine monohydrate (HMH). Reactions were carried out with different catalyst concentrations, PET-hydrazine monohydrate ratio, reaction time and reaction temperature so as to optimize the yield of the product. The product (terephthalic dihydrazide (TDH)) having potential commercial applications was characterized by CHN analysis, FTIR spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC) and X-ray powder diffractometry (XRD). The surface morphology of the synthesized product and the PET waste flakes before and during the degradation was investigated with the help of scanning electron microscopy (SEM). The process reported in this paper results in significantly higher yield (84%) of TDH in a shorter reaction time of 3 hours at a relatively lower temperature (65°C) as compared to the uncatalyzed PET-HMH aminolysis reaction.

The isolation of cellulose nanofibres from arecanut husk was achieved by a chemo-mechanical method thereby opening up a means for utilizing a waste product more effectively. The chemical processes involved alkali treatment, acid hydrolysis, and bleaching. The mechanical fibrillation was performed via grinding and homogenization. The chemical constituents at different stages of treatment of fibres were analyzed according to the ASTM standards. Morphological characterization was done using the scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The isolated nanofibers had an average diameter of below 10 nanometres and a very high aspect ratio in the range 120-150. Fourier transform infrared spectroscopy (FT-IR) showed the effective removal of the non cellulosic components. The crystallinity was increased with successive treatments as shown by the X-ray diffraction analysis (XRD). The TGA studies revealed a good thermal stability for the isolated nanofibres.

Porous tantalum has become an attractive biomaterial in several orthopedic applications due to excellent biocompatibility and biomaterial properties. This transition metal has high volumetric porosity (75%–80%), high coefficient of friction, and low modulus of elasticity (3 MPa) comparable to cancellous bone or subchondral bone. The tantalum has similar appearance to cancellous bone and is safe to use in vivo as evidenced by the use in orthopedic surgery. Currently tantalum has been used in several clinical orthopedic applications including hip and knee arthoplasty, spine fusion, osteonecrosis, cranioplasty, foot and ankle surgery, and tumor reconstructive surgery. Porous tantalum has the ability to form a self-passivating surface oxide layer which leads to the formation of a bone-like apatite coating in vivo and affords excellent bone and fibrous in-growth properties allowing for rapid and substantial bone and soft tissue attachment. The chapter discusses the biomaterial properties and orthopedic applications of porous tantalum.