Research On The Stability Of Chlorpyrifos300EW

This paper employed high-speed shearing method combined with oscillation method to screen the additives and their dosage. The orthogonal design method was then employed to optimize the formulation of chlorpyrifos EW300. The results showed that the optimal formulation of chlorpyrifos EW300was as follows:15%for xylene,2.4%for STE-200,1.6%for XY-100,2%for AEO-3P,0.15%for XG, and3%for ethylene glycol. And the quality testing results showed that the obtained optimal formulation of chlorpyrifos300EW was up to the control standards and with excellent performance.Stability index of TSl30-20h and TSl54-20h was obtained by using Turbiscan LABExpert to scan the chlorpyrifos EW300for20hours under30℃and54℃, respectively. This article studied the correlation of centrifugal stability (SC), the difference of D50, zeta potential before and after storage under room temperature of30weeks (i.e. AD50、 Δzeta) and TSI30-2011with water separation after storage under room temperature of30weeks (SR), and correlation of the difference of D50, zeta potential before and after thermal storage (i.e. ΔD’50、Δ|zeta|’) and TSI54-20h with water separation after thermal storage (ST). It turned out that there was no correlation between SC, ΔDso, Δ|zeta|and SR. It was not possible to to predicate SR, independently, by Sc, ΔDso, Δ|zeta|. The ΔD50combined with Δ|zeta|could be employed to predicate the changing direction of SR while they could not predicate the accurate value of SR. There were no accurately quantitative relationship between TSI30-20h and SR. The results also indicated that ΔD’50and Δ|zeta|’could not be used to forecast ST of the chlorpyrifos300EW. ΔD’50combined with Δ|zeta|’ could only predicate the changing direction of ST while they could not predicate the accurate value of it. However, there was a good quantitative relation between TSI54-20h and ST. Therefore, the centrifugal stability, the difference of D50, and zeta potential before and after storage could not be employed to predict the storage stability, while the TSI obtained by scanning under a certain temperature for20h could be employed to predict the physical stability of the EW that was kept under the same temperature.To take sample4that was with the best stability in the orthogonal design as study object, to take TSI gained by scanning under30℃for20h as the stability index, and to take D50, zeta potential as well as the variations of particle size and migration into concern, this paper studied the effects of processing equipment, shear time, shear speed, and the emulsifiers combination on physical stability of the EW. It manifested that the high speed shearing method could provide the emulsion system the highest energy. The particles in the system were the samlles and the physical stability was the best. The emulsion gained by stirring method that provides less energy consisted of bigger particles. Accordingly it had with bigger TSI and worse stability. TSI could not be employed to characterize physical stability of the emulsion gained by ultrasonic method because of the phenomenon of flocculation. The results aslo showed that there were critical shear time and shear speed for chlorpyrifos EW300, i.e.40min and3000r/min, respectively. The necessary energy could be guaranteed only by achieving the critical shear rate and time, but the stable equilibrium condition would be destroyed if too much energy was input and the stability will be decreased. Furthermore, when using different emulsifier combinations, the TSI of the emulsion using starchy surfactants was the biggest and with the worst stability, the emulsion using traditional surfactants was behind, and polyoxyethylene laurylether phosphate ester emulsifier AEO-3P combined with starchy surfactant could enhance the strength of the interfacial film and the stability of the gained emulsion was the best. Therefore, the optimal processing combination for chlorpyrifos EW300was to use starchy surfactant combined with AEO-3P and to employ high-speed shearing method to shear for40minutes under the speed of3000r/min.The toxic activity to Aphis craccivora was compared among the optimal formulation of chlorpyrifos EW300(SEW),480g/L chlorpyrifos ME (SME), and chlorpyrifos300EC (SEC) that gained from the market. The result showed that there were no difference among the toxic activity of SEW, SME, and SEC.Tests on particle size, zeta potential, surface tension, and wetting and penetrating time of the three formula showed that the D50of SEW was significantly larger than that of SME while there was no significant difference between the Ds0of Sew and SEC; the absolute value of zeta potential of SEW was significantly bigger than that of SME while there was no significant difference between the absolute value of zeta potential of SEW and Sec; there was no significant difference among the surface tension of SEw, SEc, and Sme, and the wetting and penetrating time of SEW and SME was longer than that of SEC·The comparison between showed that particle size, zeta potential and wetting and penetrating time had no significant influence while surface tension had significant influence on the toxicity of different formulation of chlorpyrifos to Aphis craccivora.