Effect of adjuvants on the spray droplet size of pesticide dilute emulsion

Abstract

Spray droplet size is an important factor affecting spray drift, which is directly related to the spray effect and efficiency by unmanned aerial vehicle. Effect of adjuvants on the droplet size of emamectin benzoate dilute emulsion was systematically investigated by measuring droplet size, dynamic surface tension, and rheology. The results showed that droplet size was independent of dynamic surface tension and viscosity, but was related to the viscoelastic property and strain. For the emulsions with N, N-dimethyldodecylamine-N-oxid (OA), polyalkoxylated butyl ether (LQ) and poly (vinyl alcohol) (PVA), the viscous modulus (G′′) were higher than elastic modulus (G′) under the crossover frequency, indicating that the emulsions were the viscous liquid. Furthermore, the diluted emulsions with OA and LQ had small drop, while that with PVA had big drop. These leaded to the breakup of the liquid sheet at lower deformation and the small spray droplet formation. While emulsions containing Guar gum 2-hydroxy-3-(trimethylammonio) propyl ether chloride (Gum Cl) and Sil800 (silicone adjuvant) exhibited a weak elastic behavior, and had the large droplet size. In addition, compared to the emulsions with OA, LQ and PVA, the dilute emulsions with Gum Cl and Sil800 had the large drop diameter, and G′ had a rapid decrease at bigger strain. This suggested the dilute emulsions with Gum Cl and Sil800 had a high stability during atomization. The study would provide a useful guide for selecting drift control adjuvants and raising pesticide efficiency.