Drift Reduction Agent has been defined in ASTM Standard E1519 Terminology Relating to Agricultural Tank Mix Adjuvants as “a material used in liquid spray mixtures to reduce spray drift.” ASTM Standard E609 Terminology Relating to Pesticides defines drift as “the physical movement of an agrochemical through the air at the time of application or soon thereafter to any non- or off-target site. Drift shall not include movement to non- or off-target sites caused by erosion, migration, volatility or wind blown soil particles that occur after application unless specifically advertised on the label.” Because there are many commercial tank mix adjuvants designed to reduce spray drift, there is a need to establish an ASTM Standard Test Method to evaluate their effectiveness. ASTM Standard E2798 is the new test method developed for the Characterization of Performance of Pesticide Spray Drift Reduction Adjuvants for Ground Application. This paper presents the data generated from the round-robin testing of this method. The method provides guidelines for the measurement of parameters pertaining to the performance of drift reduction adjuvants under simulated field application conditions. The measurements can be made in a wind tunnel or a spray chamber. The method describes the preparation, composition, and test/application conditions for droplet size, spray pattern measurements, and fines reduction. The exact selection of application conditions such as nozzle type and tank mix partner may vary according to the intended use conditions.
A new family of dispersants for agrochemical suspension concentrate (SC) formulations has been created by reacting an anhydride-bearing resin with a methyl capped polyether amine. The result is a moderate molecular weight graft polyamide, with the desirable “comb” geometry. From this family of materials, four were chosen for comparison to three commercially available benchmark dispersants in several typical pesticide suspension concentrates. The criteria used to compare the new to the old dispersants were: ability to reduce suspension viscosity, zeta potential, syneresis, and tendency of the concentrate to “hardpack.” The study demonstrated that the new dispersants are generally very effective dispersants, but care must be used in selecting the best dispersant/wetting agent combination for a given pesticide formulation.
A novel flow cell has been developed to observe on a microscopic level the steady state, cocurrent flow of two pre-equilibrated phases in a porous medium. It consists of a rectangular capillary tube packed with a bilayer of monodisperse glass beads 109 microns in diameter. The pore sizes in the model are of the order of magnitude of those in petroleum reservoirs.An enhanced videomicroscopy and digital imaging system is used to record and analyze the flow data.Several fluid systems covering a wide range of interfacial tensions were studied using a syringe pump capable of producing superficial velocities ranging from 0.1 to 2,000 ft/day. While most of the work employed an injection ratio of 1:1, experiments with various ratios up to 10:1 were performed. At low capillary numbers, the expected stable, continuous, tortuous paths were observed.At a capillary number of about 0.001 the nonwetting phase started to flow freely as large ganglia having lengths of 10-20 pore diameters in the direction of flow. As the capillary number was further increased, these ganglia became shorter, reaching the size of a single pore at a capillary number of about 0.01. When the capillary number was increased above this value, ganglion or drop size continued to decrease to values below the pore throat diameter.Eventually the small drops stretched out, producing a filament type flow.The success of waterflooding as a petroleum recovery process and the realization that even it leaves behind a substantial amount of residual oil have been major factors stimulating research on twophase flow in porous media during the past fifty years. Most of the knowledge pertinent to two-phase flow under normal waterflooding conditions is summarized in existing books (1^4).Recently, the
Twelve commercial drift reduction agents were evaluated for their characteristics in the three most commonly accepted parameters for spray droplet size formation—extensional viscosity, dynamic surface tension, and kinematic viscosity. Samples were sprayed in both water and in the presence of a commercial herbicide formulation. The spray droplet spectra for these agents were then determined under rigorous control, in still-air conditions, using a Sympatec HELOS/KF laser diffraction particle size analyzer. Spraying an actual pesticide formulation that contains a wetting agent is important because the surfactant present reduces dynamic surface tension and can significantly reduce spray droplet diameter. The aerosol particle size distributions were measured using an electronic actuator that moved the nozzle spray pattern through the laser in a reproducible manner. There are multiple mechanisms that can influence both volume mean diameter and percent fines below 105 microns. There are natural and synthetic water-soluble polymers that function by increasing extensional viscosity. There are oil products that produce emulsions that keep small spray drops from forming. The droplet spectra for the different commercial products were grouped according to their specific drift reduction mechanism in order to see if a better correlation could be made on how they individually affected the resulting droplet particle size distribution.
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