Effects of Spray Adjuvants on Spray Droplet Size from a Rotary Atomizer

Rotary atomizers are used in a number of aerial applications, such as forest pest spraying and mosquito control sprays. These types of atomizers have a rotating cage at speeds of 2,000 to 10,000 revolutions per minute (rpm) through which a spray is emitted and atomized. Many applicators routinely add spray adjuvants to change the droplet size, reduce drift potential, or to reduce evaporative effects of a particular spray solution; therefore, six commonly used classes of spray adjuvants were evaluated to determine their effects on droplet size. If an applicator's only concern was minimizing spray drift, the applicator could choose a polymer or high surfactant oil concentrate for helicopter speeds and a polymer for fixed-wing applications. For applicators working under hot, dry conditions where evaporation is a concern, choosing an oil-based adjuvant to help get better coverage by creating smaller droplets that do not evaporate would be recommended. Understanding the role the different adjuvant types play in the final droplet size of the spray is key to successfully setting up and making applications with rotary atomizers.