Studing On The Properties And Mechanism Of The Formation Process Of Alachlor Emulsion In Water

The following aspects were studied in this thesis :1. We have screened out the emulsifers, cryoprotectan and suspending agent by measuring the particle size and stability of different formulations of acetochlor emulsion in water, then the best formula of acetochlor emulsion in water was ascertained as follows: Span80:Tween20= (the rate of weight as1.2:1): 5% N-butanol:3% Glycerol: 5% ; The 67%solution of Alachlor in dimethylbenzene:30% ; The rest was water.2. The rheological characteristics of Alachlor emulsion in water was measured. The results showed that its fluid form behaves as plastic fluid and its viscosity was lowered in extent with temperature raises.3. Formation of emulsions has been studied in the system water/Tween20+Span80/alachlor by six emulsification methods: a: stepwise addition of a water-surfactant mixture to oil, b: stepwise addition of water to a oil-surfactant mixture, c:stepwise addition of oil to a solution of surfactant in oil, d:stepwise addition of a oil-surfactant mixture to water. e:Tween20 in water and Span80 in oil , stepwise water in oil.f: Tween20 in water and Span80 in oil ,stepwise oil in water .Their particle size was determined by laser particle sizer, and their stability mechanisms were derived from determining their rheological characteristics and verified by the microphotographs. The results indicate that the emulsions that produced by different emulsification methods have different particle size distributions . Significant difference exists on drop size, drop size distribution, emulsion stability, and structure when emulsion was produced under different emulsification processes. For the different micellization and absorption ability of emulsifier in water phase and oil phase, the drop size is smaller and emulsion liquid is more stable when emulsifier is added to oil phase first for the ultra-low interfacial tension developed during phase inversion. Three-dimensional network generates for the weak flocculation among drops, and this structure delay the sedimentation.4. The particle size, microstructure and rheological characteristics of acetochlor emulsions prepared by different emulsification processe were further studied by particle determination, conductivity and viscosity methods.The results show that the viscosity for the system prepared by phase inversion methods both passed a maximum value with the content of water varied, and the moment of which the droplets were closed-packed in microstructure.