Many factors, including adjuvants, pesticide formulations, and nozzle tips, affect spray droplet size. It is important to understand these factors as spray droplet size affects both drift and efficacy of pesticides, which is a main concern with pesticide application. A laser particle analyzer was used to determine the spray droplet size and distributions of a range of formulations sprayed through several types of nozzle tips. Nozzles included were extended range flat fan sizes 11003 and 11005 ͑Spraying Systems XR͒, air induction flat fan sizes 11005 and 11004 ͑AI͒, air induction extended range flat fan size 11005 ͑AIXR͒, preorifice flat fan size 11005 ͑TT͒, and a second preorifice flat fan size 2.5 ͑TF͒. Several deposition/ retention adjuvants were studied, including Array, Interlock, In-Place, and Thrust. Another study looked at diflufenzopyr ϩ dicamba ͑Status, BASF͒ in combination with several adjuvants. Also, three fungicides were evaluated at differing spray volumes. Results indicated that the droplet size of some nozzle tips is more affected than others by changes in the contents of the spray solution.
Concentrated aqueous emulsions, or EWs, are the dispersion of a water insoluble organic liquid into water. The formulation is achieved through the use of polymeric surfactants, which provide multiple anchoring points and steric stabilization to prevent coalescence. Formation of the EW is mechanically driven, requiring high-shear processing to reduce particle size and attain a stable formulation. In this study, the relationship between processing shear time, particle size, and stability was examined. Samples were prepared using a high hydrophile/lipophile balance (HLB) polymer (butyl block copolymer) paired with a low HLB polymer (nonionic block or random copolymer), varying polymer types and polymer ratios. Shear was applied for 10 min to 40 min. Emulsion dilution stability (ASTM E1116-98), particle size distribution (Malvern Mastersizer), and high temperature stability were used to characterize the samples. It was found that particle size decreased as shear input was increased, reaching an optimum after 25 min to 30 min of shear, depending on the polymer pair used. All samples performed similarly in dilution stability showing improved performance after 10 min of shear. After 1 month at 54°C, all samples showed no separation and demonstrated similar dilution performance, however, D90 values dropped significantly (>20 %) in samples with less than 20 min of shear, whereas samples receiving a minimum of 20 min to 30 min of shear showed decreases in D90 around 10 %. A likely explanation for the decreases in D90 observed after elevated temperature storage is that the addition of heat energy drove the particle surface area toward equilibrium according to the equation ΔA=W/γ, where ΔA is change in surface area, W is work, and γ is interfacial tension
The foam that is generated in agricultural tank mixes is of great concern because this foam can cause problems such as slow mixing and worker exposure. Antifoaming and defoaming agents are used to control this foam. Developing a reproducible test that accurately predicts the real world performance of these products has been difficult. Several methods are briefly reviewed. An ASTM method has been developed and established. However, this method intuitively is difficult to translate into real world performance. An older possible method has been shown to have obvious and significant problems. Several new modifications to this older method are proposed as a means of overcoming the problems and measuring the performance of products. The proposed method involves a large, polypropylene beaker that is charged with a foaming solution. The solution is stirred and foam is generated using an air sparge and a sparge stone defined in another current ASTM method. Defoamer is added to the foam and the time required for the foam to collapse and to reform is measured separately. The way the foam disintegrates and redevelops can also be observed and recorded or described. Statistical data indicate that, using this method, differences between the performances of various defoaming/antifoaming agents can be determined. The differences are reproducible enough to identify performance differences that will be appreciable in the field. As a result, quantitative and qualitative data may be generated using the proposed method. Also significant is that the method separates antifoaming and defoaming into discrete measurements. This separation of the two measurements provides a better measurement for how a product will perform in the field relative to other products. Calculations resulting in new terms are proposed as a means to create a scale that will allow direct comparison of the performance of various antifoams/defoamers.
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