| Pesticide emulsion formulations (Emulsion in water and Microemulsion) is one of the development direction for water-based pesticide formulations. The emulsion formulations ca n effectively reduce the leakage of solvent, which is green pesticide formulations, and it h as the advantages of safety, efficiency and environmental protection. However, pesticide e mulsion formulations belong to the thermodynamic instability system, the physical stability affected by many factors. In the process of production, processing and transport storage pr one to delamination, coalescence, austenite slaking, oil, emulsion such as instability, and ot her issues. Therefore, the stability is an important subject of pesticide emulsion pesticide f ormulations. The properties of oil-water interfacial film is the most important factors for t he stability of pesticide emulsion formulations. Interfacial dilational vis-elasticity properties is on of the most important factors of interfacial film. The study of the dilational rheolog y can make contribution to the more profound understanding of the microscopic structure of the interface, which is important scientific significant for elucidating the stability mecha nism of pesticide emulsion formulations, and may be deeply reflecting the internal relaxati on process.In this paper, the dilational viscoelastic properties have been investigated by means of oscillating drop method. The different techniques, sinusoidal oscillations and interfacial te nsion relaxations, have been used to study the different experiment. The relationship betwe en the hydrophobic group structure of series Tween surfactants and rheological properties, In view of the different preparation ways of emulsion, examines the interfacial film proper ties, studies the interaction of non-ionic surfactant and protein, non-ionic surfactant and wa ter soluble pesticides. The aims of this study is providing a scientific and reasonable use, in depth understanding of pesticide emulsion preparation processing, and greatly improve t he stability of pesticide emulsion preparation system to the theoretical foundation. The exp erimental results are as following:1. The larger quantities of the Tween20molecules with shorter hydrophobic chain len gths were adsorbed at the interface because they could arrange more closely. Tween40and Tween60molecules had similar "actual cross-sectional areas", which meant that their inter facial tensions were also similar at the critical micelle concentration (IFTcmc). Furthermore, when the bulk concentration exceeded the critical micelle concentration (cmc), the modulus and elasticity of Tween20was larger than those of Tween40and Tween60. When the hy drophobic alkyl chain of TweenX reached a certain length, the interfacial film properties o f TweenX affected by the hydrophobic chain length decreased, which led to similar dilatio nal parameters. The interfacial activity of Tween80is rather large compared to Tween60. The Amin value of Tween80is a little large than that of Tween60, which is due to the s teric effect of unsaturated double bond in Tween80molecule. The dilational data show tha t the ethylene oxide groups of non-ionic surfactant form a stable sub-layer, which results i n the increase of modulus and the decrease of phase angle for both Tween60and Tween80than those of common ionic surfactants. Moreover, the unsaturated hydrophobic group of Tween80is much flexible, which are easily crosslinked and entangled. Therefore, dilation al modulus of Tween80is higher and phase angle is lower than that of Tween60. Low te mperature decrease the flexibility of unsaturated hydrophobic group and less influence on t he interaction of saturated hydrophobic group. Saturated surfactant molecules of Tween60a lmost lost temperature response. Three hydrophobic long chains compared with single one chain, the interfacial properties significant changed, the interfacial properties of Tween65is similar to the polymer and protein.2. The interfacial film formed by Span80and Tween80from oil phase adsorption, the space of hydrophilic PEO groups is larger, which results in increased with the percentage of Tween80(namely Span80ratio decrease), interfacial film molecular interactions graduall y weakened, elasticity modulus, structure modulus increase to plateau value, interfacial fil m controlled by slow relaxation process. However, the interfacial film formed by Span80and Tween80from oil phase and aqueous phase adsorption, Tween80gradulally replace int erface of Span80molecules. With the increase in the percentage of Tween80(namely Spa n80ratio decrease), elasticity modulus, structure modulus increase to plateau value, interfac ial film controlled by the slowest relaxation process. Interfacial film properties of the diffe rent adsorption ways can find that oil phase adsorption of interfacial activity, viscosity and static modulus is larger than oil phase and aqueous adsorption interfacial film. The two t ypes of adsorption mechanism is completely different. Moreover, PEO groups from oil pha se adsorption cannot form sub-layer structure.3. Surfactant408and protein β-LG competitive adsorption at the interface. During the low concentration range, Silwet408and β-LG form the compound by hydrophobic interact ion, which led to the dilational modulus of β-LG/Silwet408mixed system is larger than th e pureβ-LG. With the increase in the bulk concentration, the β-LG gradually replace by th e surfactant molecules, the rigidity of the film is gradually weakened, but the β-LG is not be complete replaced, which results that the interfacial tension curve at high concentratio n is not overlap, and the interfacial pressure gradually reduce with the increase of surfacta nt concentration.4. The addition of1wt%glyphosate isopropylamine significant influence on the PO EA surface tension and dilational properties. The dilational modulus, dilational elasticity an d dilational viscosity obvious decrease in general, and the values of phase angle significan t change after the addition of1wt%glyphosate isopropylamine. Glyphosate isopropylamin e and POEA form a new complex in the solution and the surface activity and surface dila tional properties of complex is different from POEA. Different from POEA, the electrolyte of glufosinate ammonium and glyphosate isopropylamine significant enhance the surfactant molecules diffusion and exchange, and reduces the Tween80ability of interfacial deformat ion resistance by Marigoni effects. Glyphosate isopropylamine salt prominent enhance the diffusion and exchange. |
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