Interactions between polymer and surfactant can significantly affect solution properties, but little is known as to how these changes impact spray drift. Effects of conformation change caused by association between polymers and surfactant systems (in a model agrochemical mixture) on spray performance in terms of droplet size and spray drift through a flat fan nozzle were investigated. The physical properties of polymer/associative and polymer/non-associative surfactant systems (Poly(ethylene oxide) (PEO)/sodium dodecyl sulphate (SDS) and PEO/Tween20, respectively) were compared. All polymer-surfactant solutions were characterized by dynamic surface tension (DST), shear rheometry and capillary break-up extensional rheometry (CaBER). Results obtained from the two systems indicated that associative and non-associative surfactants perform differently in terms of their capacity to affect solution properties. For PEO/SDS system, substantial decrease in DST, significant increase in shear viscosity at zero shear rate and longest relaxation time (as determined from CaBER, which represents extensional viscosity of solutions) were observed after addition of SDS, and they changed consistently with SDS concentration. However, these were not seen with PEO-Tween20 system. Droplet size and spray drift were also measured. Drift was effectively reduced as SDS concentration comes to 2CMC, indicating that the changed conformation by molecule association from this point was capable to contribute to drift reduction. Dynamics of extension was found the dominant factor dictating drift. The drift reduction produced by the PEO/SDS system was found significantly correlated with the liquid physical properties (R2 = 0.84 and 0.82 for DST and relaxation time respectively), while this was not true for the PEO/Tween20 system. This study showed the advantages presented by PEO/SDS over PEO/Tween20 system in spray performance through a flat fan nozzle, which indicated the potential for utilizing polymer/associative surfactant systems in spray mixtures when drift is of primary concern.

How conformation change in polymer-surfactant system influence spray performance through flat fan nozzle

248th National Meeting (2014)

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