Effect of Temperature and Pressure on Spray Properties of Tapioca Starch Adhesives

The use of starches as a material in urea granules coating industry is a recent development. The pure starches do not meet the standards set by many industrial processes due to slow tacking and to low viscosities, and require necessary modifications in their physical properties. The objective of the work was to synthesize and characterize the tapioca base biopolymers for future urea granules coating applications. For this purpose, three compositions of starch-urea-borate complex were prepared and their sprays were characterized using a bottom to top spraying system. The characterization of physical properties of the synthesized starch adhesives was carried out by determining the effect of temperature, shear rate and mass concentration of thickener/stabilizer on solution viscosity. A shear-thinning behavior followed by shear-thickening was observed for all solution compositions. This shear thinning to shear thickening transition becomes less prominent above 80°C of solution heating temperature. Using a high speed camera (Phantom v9.1), the jet breakup dynamics were also visualized as a function of the solution temperature and pumping pressure. . An increasing trend was noticed in spray cone angle with temperature upto 80°C and thereafter it became almost constant. Similarly, a linear increase in spray tip penetration was noticed with time from start of the injection which became steady after 70 ms of injection time.