The performance of an accelerated drying system for drying of skim natural rubber laces

Abstract

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 0C. 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 0C) 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.