SEDL / STP / STP1347-EB / STP14157S

Effects of Adjuvants and Dynamic Surface Tension on Spray Properties Under Simulated Aerial Conditions

Dexter, WR
Research Fellow, Agricultural Research Center, American Cyanamid Company, Princeton, NJ

Huddleston, EW
Professor, Plant Pathology and Weed Science, New Mexico State University, Las Cruces, NM

Pages: 12    Published: Jan 1998

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Abstract

The literature on the effects of active ingredients, adjuvants and surface active agents on the droplet size of agricultural sprays is reviewed. The effects of various agricultural adjuvants on the droplet size distributions of a herbicide sprayed in a wind tunnel simulating an aerial application were determined using a Malvern laser diffraction instrument. All adjuvants caused a decrease in droplet size, which varied with adjuvant type and concentration. Measurements of equilibrium surface tension, dynamic surface tension at 20 ms, density, and viscosity were recorded. Droplet size did not correlate linearly with equilibrium surface tension: only at the lowest surface tensions was any significant decrease in droplet size observed. Droplet size correlated better with dynamic surface tension for each adjuvant over most of the surface tension range, but with different slopes for each adjuvant. At high concentrations of surfactant, bubbles of air were observed within captured droplets and the size distribution became bimodal.