Search

Accelerator functional character was introduced on nanosilica by chemical reaction of sodium isopropyl xanthate (SIPX) with nanosilica (NS). Functional characteristics of nanosilica were confirmed by elemental analysis, thermogravimetric analysis, and infrared spectroscopy. This SIPX functionalized nanosilica (SIPX-NS) incorporated natural rubber (NR) composites were used to evaluate the dispersion of silica in rubber and also the interaction between rubber and filler. The finely dispersed SIPX-NS particles in the NR matrix are revealed from the morphological analysis. Subtle changes in the surface chemistry of silica had a profound influence on dispersibility in the NR matrix. NR 4SIPX-NS composite showed an increase in tensile strength by 10%, flex crack initiation resistance by 13%, tensile strength retention by 16% and cure time reduced by 2 min relative to those of NR 3NS composite. This simple, efficient and cost-effective surface modification of silica improved the vulcanization efficiency and mechanical performance of NR composites and has great potential in the fabrication of high-performance polymer composites.

In this work an alternative route to produce nanosilica using a low cost raw material –olivine is suggested. Nanosilica is produced by the dissolution of olivine in acid. The olivine dissolution is a low temperature process making this process cheaper and greener. The amorphous, pure nanosilica obtained had a surface area of 289 m2/g and a particle size between 9-15 nm. The synthesized nanosilica was used to prepare natural rubber composites in a Thermo Haake internal mixer. Mechanical properties registered significant improvement with tensile strength, tear strength and modulus showing 45%, 57% and 47 % increase, respectively.

Accelerator functional character was introduced on nanosilica by the chemical reaction of sodium isopropyl xanthate (SIPX) with nanosilica (NS). Functional characteristics of nanosilica were confirmed by the Elemental analysis, thermogravimetric analysis, and infrared spectroscopy. This SIPX functionalized nanosilica (SIPX-NS) incorporated natural rubber (NR) compounds were used to evaluate the dispersion of silica in rubber and also the interaction between rubber and filler. The finely dispersed SIPX-NS particles in the NR matrix are revealed from the morphological analysis. Subtle changes in surface chemistry of silica had a profound influence on the dispersibility in NR matrix. NR 4SIPX-NS composite exhibited improved cure time, tensile strength, flex crack resistance and aging resistance relative to those of NR NS composite. This simple, efficient and cost-effective surface modification of silica improved the vulcanization efficiency and mechanical performance of NR composites and has great potential in the fabrication of high-performance polymer 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.

Dynamic mechanical behaviour of natural rubber-silica composites was studied by a frequency sweep method at different temperatures (40 °C,70 °C and 100 °C) using a dynamic mechanical analyzer and a rotorless rheometer, RPA, in an attempt to establish a correlation between the two. The composites with silica content up to 40 phr were studied. It was found that the dependence of dynamic modulus on the frequency as obtained from both the instruments followed a similar trend. This suggests that the dynamic mechanical properties of rubber compounds can be determined even during curing. A correlation could be arrived at between the two sets of data, making it possible to predict one set knowing the other. The impact of silane coupling agent, bis (3-triethoxysilylpropyl tetrasulphide), TESPT, on viscoelasticity was also investigated. The mechanical properties were improved in the presence of TESPT. Additionally, an increase in thermal stability was also observed in the presence of TESPT. Scanning electron micrographs showed the better filler dispersion in the case of silane-coupled silica composites.

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.

Multiwalled Carbon nanotubes (MWCNTs) were covalently functionalized by H 2 SO 4 /HNO 3 treatment to produce Carboxylated Multiwalled Carbon nanotubes (MWCNTR). Presence of carboxyl moieties on MWCNT were confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Thermo gravimetric analysis (TGA). These hydrophilic polar groups helped in getting stable aqueous dispersions of nanotubes. High performance composite with good mechanical and electrical properties was prepared by ultrasonication assisted mixing of aqueous dispersions of MWCNTR with natural rubber (NR) latex followed by film casting and curing. A segregated network of nanotubes was formed along the boundary of latex spheres even at low concentration which is evident from very low percolation threshold (0.086 vol%), high conductivity and dielectric constant. The network formation was confirmed by TEM and supported by strain sweep studies. The tensile strength increased by 61%, tensile modulus by 75% and tear strength by 59% by the addition of 0.5 parts per hundred rubber (phr) MWCNTR. The inclusion of 1.0 phr MWCNTR in the NR matrix increased the dielectric constant from 4.7 for pure NR to 918 at 100 Hz. The AC conductivity reached a value of 10 −4 S/m for the nanocomposite. This nanoscale, flexible, reinforced natural rubber based composites with high dielectric constant and conductivity could find application as electromagnetic wave absorbers in the low frequency region.