Yield Optimization of Spray‐Dried Natural Rubber and Properties of Its Silica‐Filled Composite

Abstract

ABSTRACTNatural rubber powder (NRP) was prepared by spray drying and optimized via statistical experimental design. The yield of NRP obtained significantly depended on the percentage of dry rubber content (DRC) and the amount of sodium dodecyl sulfate (SDS). The optimum condition for spray drying was found to be with an inlet air temperature of 130°C, a feed rate of 4 mL min−1, nozzle flow rate of 600 L h−1, 15% DRC, and 12 parts per hundred of rubber (phr) of SDS. Under these conditions, a NRP yield of 44.9%, and a total solid recovery of 98.7% with a moisture content of 0.4% was obtained. The resultant NRP particles were almost spherical with a diameter of less than 10 μm. The mechanical properties of NRP, in terms of the modulus, tensile strength, and hardness were greater than that for conventional block rubber (STR). Moreover, the addition of silica filler (25 phr) yielded better mechanical properties when prepared by spray drying (Si/NRP) than by the conventional silica‐filled block rubber (Si/STR). Scanning electron microscopy revealed that the silica was more remarkably evenly dispersed in the rubbery matrix of the Si/NRP composite compared to the agglomerated clumps found in the Si/STR composite prepared by the conventional mechanical mixing method.