Purpose: Rice husk is burnt and discarded without effective use; however, it is a reliable resource that can be used to extract silica from its ash (RHAS) and can be incorporated in rubber blends as filler. The effect of Natural rubber (NR) and Acrylonitrile-butadiene rubber (NBR) ratio of NR/NBR blends filled with RHAS on physico-mechanical, and swelling percentage in specific oils (brake oil, hydraulic oil, engine oil) and toluene were studied since these blends have potential applications like fluid sealing.Methodology: RHAS was extracted via sol-gel method and characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopic (FTIR), and Scanning Electron Microscopic (SEM) analyses. NR/NBR blends with different NR to NBR ratios (100:0, 80:20, 60:40, 40:60, 20:80, 0:100) were prepared by incorporating 25 parts per hundred parts of rubber and curing characteristics, physico-mechanical and swelling properties were evaluated. Findings:The XRD, FTIR, and SEM analyses confirmed that the RHAS contains silica with a combination of nanoparticles and large agglomerates. The blends showed preferable curing characteristics while the hardness, compression set, and tear strength of blends ranged from 60-70 International Rubber Hardness Degrees, 0.5-6%, and 10-20 N/mm, respectively. Although the tensile properties (before ageing) were low, the retention of tensile strength after ageing was better in NR/NBR blends. Blends with high NBR proportion showed tolerable swelling against toluene, hydraulic oil, and engine oil while blends with low NBR proportion showed better swelling resistance to brake oil. Limitations: Time was limited to evaluate the properties of blends with different loading levels of RHAS.Value: There is a potential to use these NR/NBR blends in applications like fluid seals which require oil resistance and toluene resistance, where 0.5-6% and about 60-100% swellings are tolerable, respectively, compromising the physico-mechanical properties meanwhile replacing carbon black in respective applications.

Organoclay (OC) filled natural rubber (NR) latex crepe was prepared in view of investigating the effect of organoclay on raw rubber properties and viscoelastic properties by incorporating aqueous dispersion of OC clay into NR latex followed by conventional acid coagulation procedure. Raw rubber properties of OC filled fractionated bleached (FB) and unfractionated unbleached (UFUB) crepe rubber were evaluated to characterized the composite samples in comparison to standard crepe rubber whilst process based characterization was carried out with Moony viscosity and Mooney relaxation data. Raw rubber properties have shown that OC acts as a pro-oxidant and as a result, Initial Plasticity (Po) and Plasticity Retention Index (PRI) which measures the thermo-oxidative degradation were negatively affected. Viscoelastic behaviour, as measured with low shear strain rate flow properties, is significantly affected by the addition of OC into the NR latex. Reduction of Mooney viscosity of OC filled crepe rubber has been explained with thermal oxidation as a result of metal impurities in the OC and plasticization caused by the organic modifier of the OC. Mooney stress relaxation has shown that lower clay loading provides a better processability and dispersion of OC within the crepe rubber.

Properties of natural rubber (NR) and acrylonitrile butadiene rubber (NBR) blends are varied due to blending method. The literature is evident that the pre-blending and phase-mixing methods affect the properties of blends while opposite arguments are also available. Hence, that fact was interested to study using NR/NBR blends filled with rice husk ash nano silica (RHANS) having an average particle size of 50 nm - 100 nm with some micro-scale agglomerates. The structure of RHANS was proved using X-ray diffraction and Fourier transform infrared spectrophotometric analyses. Blends were prepared following both blending methods by varying NR to NBR ratio as 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 while filling 25 parts per hundred parts of rubber of RHANS. The control was the ASTM formulation for oil seals. Vulcanization properties of blends showed acceptable levels with extended scorch and cure times and high torque properties. Blends indicated less tensile and tear strength compared to the control while showing acceptable hardness, compression set, and swelling properties. Overall, there is a possibility to use RHANS in NR/NBR blends and it was found that the blending method does not affect the properties of the NR/NBR blends.

In this study, cellulose fibre was extracted from banana pseudo-stem and converted into cellulose whiskers (CWs) with high-pressure defibrillation method. The CWs were characterized using FTIR, XRD and the results conform the structure of cellulose. XRD studies showed that the percentage crystallinity of bleached fibres is about 93%. The particle size analysis showed a bimodal distribution for CWs where approximately 21% of the sample has average size of 110 nm. The rubber compounds were prepared according to a general tyre tread formulation while incorporating the purified CWs in diluted centrifuged latex (NR) followed by converting them into rubber sheets to produce cellulose whiskers/natural rubber CW/NR composite. Meanwhile, the control was prepared without incorporating CW in the diluted centrifuged latex. The lowest Mooney viscosity and the highest stress relaxation coefficient of CW/NR composites ensured higher processability. Curing characteristics of the compounds were evaluated at 120 °C and physical properties were evaluated on par to the ASTM standards. The highest cure rate and better scorch time were observed in CW/NR composite. Most of the physical properties were superior. In overall, it is obvious that cellulose whiskers have a potential to use as reinforcing material for natural rubber tyre tread compounds.