Influence of surfactants and polymeric adjuvants on physicochemical properties, droplet size spectra and deposition of fenitrothion and Bacillus thuringiensis formulations under laboratory conditions.

The effect of two surfactants and two polymeric adjuvants on droplet size spectra and deposition patterns of nine spray formulations was investigated following atomization in a laboratory chamber using a spinning disc atomizer that can produce a narrow droplet size spectrum. Spray droplets were sampled using Kromekote cards and deposit recoveries were examined on glass plates. Physicochemical properties studied were: viscosity-shear rate relationship, surface tension, volatility, pH, conductance, electrophoretic mobility and zeta potential. Formulations containing low surfactant concentrations provided Newtonian liquids with low viscosities. These liquids atomized into small droplets and provided low recoveries of spray deposits on sampling units. However, formulations containing polymeric adjuvants, and a high concentration of a non-ionic surfactant provided pseudoplastic liquids with high viscosities. These formulations resulted in large droplets with high recoveries of spray deposits on sampling units. Among the physicochemical properties studied, viscosity, surface tension, volatility and electrophoretic mobility, played important roles on liquid atomization and droplet deposition.