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Cellulose nanofibrils with a substantial aspect ratio (100–150) were isolated from an abundant agricultural waste, arecanut husk. These cellulose nanofibrils were incorporated into natural rubber (NR) latex and the resulting composites were investigated for rheological, dynamic mechanical, physical and thermal properties. Rheological and dynamic mechanical analysis of the composites were carried out as a function of fibre content, frequency and temperature using Rubber Process Analyser (RPA) and Dynamic Mechanical Analyser (DMA). All the systems registered rise in elastic response with increase in frequency. RPA studies showed that the nanocellulose fibrils had a profound influence on the rheological behaviour of the composites. The rheological percolation threshold of the composites was obtained to be between 2 to 4 phr. The dispersion of nanofibrils in the composites was investigated using Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). An extensive network formation in the NR matrix, credited to the higher aspect ratio of nanofibrils, imparted the composites with improved mechanical properties. Cellulose nanofibrils do not inflict any detrimental effect on the thermal profiles of the composites. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]