Natural rubber (NR) latex-clay nanocomposite (NRLCN) synthesized with montmorillonite (MMT) clay aqueous dispersion was evaluated for reinforcement and barrier properties. The physio-mechanical properties of the NRLCN were compared with the conventional NR latex composites containing CaCO 3. The NRLCN structure was characterized with X-ray diffraction and scanning electron microscope techniques. The X-ray diffraction data showed that, with a lower concentration of clay, a highly exfoliated clay structure was achieved whilst the clay aggregation gradually resulted in a higher concentration of clay. The crosslink density as computed based on the solvent absorption data of the latex nanocomposite films was increased with the increase of clay concentration. As a result of nanoscale dispersion of the montmorillonite clay and higher crosslink density of the latex nanocomposite films, the resistance to permeation of small molecules through the NRLCN was significantly enhanced in comparison to conventional NR latex-CaCO 3 composites. Solid state mechanical properties of NRLCNs showed a significant reinforcement effect of dispersed clay platelets but without significantly reducing the elastic properties. The higher mechanical properties and improved barrier resistance indicated that NR latex nanocomposites containing montmorillonite clay is a potential replacement for conventional NR latex composites containing CaCO 3 .
A dryer consisting of a saw dust fed furnace and a drying chamber was designed and fabricated for drying of skim natural rubber laces using hot smoke. Uninterrupted drying of laces was carried out in warm smoke in three different temperature ranges. Drying performance was evaluated in terms of raw rubber properties and drying period to achieve complete dryness. Quality of laces was assessed by visual appearance. The best temperature range for drying of skim natural rubber laces was found to be 30-34 0 C. Drying efficiency of laces was accelerated by more than 60% without affecting its raw rubber properties when laces were dried at this temperature range. The resistance to mould growth of dried laces was also improved. However, the dried product was downgraded according to the visual quality assessment in terms of colour which is commonly practiced in the trade for grading of rubber. Therefore, heating mechanism was modified to provide a draft of clean warm air into the drying chambers where the laces were hung for drying. The drying temperature inside the chambers was maintained at the selected temperature range (30-34 0 C) and drying of laces was completed within twenty-four hours. It was able to obtain skim laces with improved colour. Drying curve for skim laces dried using accelerated drying system was derived. Results of tests carried out to determine the raw rubber properties of laces showed that raw rubber properties of skim laces were not affected due to accelerated drying within the selected temperature range. Mechanical and physical properties of 80/20 (w/w) blends of Technically Specified Rubber (TSR 20)/ambient air dried skim laces and the blends of TSR (20)/warm air dried skim laces were also compared. The properties studied were tensile properties, hardness, compression set and resilience. The results suggest that warm air drying of skim laces has no significant effect on the mechanical and physical properties of the blends of TSR/skim laces.
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