Agricultural application of phosphate ester-containing surfactants, compatibility relationships, and synergies in complex tank mix systems.

Abstract: Agricultural crop protection relies on a variety of formulated chemicals, including insecticides, fungicides, herbicides, growth regulators, and micronutrients. To maximize yield, quality, or prevent disease, multiple commercial formulations are often combined. However, as the complexity of tank mixes increases, incompatibilities may arise. Phosphate ester-containing surfactants have been shown to reduce or prevent these incompatibilities and enhance hard water tolerance, which is crucial for maintaining the intended performance of agricultural formulations.

To better understand the chemical interactions that influence the compatibilization properties of phosphate ester surfactants, tank mix systems combining broad-spectrum herbicides with emulsified additives were treated with various phosphate ester surfactants prepared under similar synthesis conditions. Compatibility was evaluated based on visual quality and stability over time, considering varying storage temperatures and hard water ion concentrations. The surfactants were synthesized using a range of hydrophobic and hydrophilic moieties, varying in carbon chain length, alkoxylation degree, aromaticity, and branching.

Results indicated that specific hydrophobic segments of phosphate ester surfactants reduced incompatibility between glyphosate and atrazine. Comparisons with nonionic surfactants demonstrated that the phosphate ester functional group enhanced compatibility and emulsion quality in selected tank mixes. Further comparisons with sulfate-based surfactants revealed that phosphate ester surfactants provided superior tank mix compatibility, quality, and stability. Notably, certain phosphate ester surfactants containing aromatic hydrophobic components showed inconsistent compatibility performance in relation to hard water ion concentrations. Additionally, synergistic blending of certain phosphate ester chemistries improved tank mix compatibilization while enhancing heat and hard water tolerance.