Effect Of The Different Wall Material Of Beta-cypermethrin Microcapsule Suspensions On The Differences Of Application And Enviroment Characteristics

Pesticide micro-capsulation have many advantages such as prolong controllingeffect, improve using efficiency, avoid decomposition, avoid volatility and invalidation, abate toxicity and harmfulness, reduce environment pollution, and so on. At present,researches on pesticide microcapsules are mainly focus on screening the recipe,optimizing the process conditions of preparation,and characterizing the release, etc.There were few reports about the difference on releasing, degradation, migration,surface retention of the different wall material microcapsules in the pesticideapplication, and degradation of the wall materials. Urea-formaldehyde （UF） and melamine-formaldehyde resin of beta-cypermethrin microcapsules were prepared byin-situ polymerization, and polyurethane and polyurea by the interfacial polycondens-ation respectively. Release characteristics of four microcapsules were studied inorganic solvents.The photolysis difference of prepared microcapsules was studiedwith UV and natural light, and the degradation of four wall materials under UV light.The mobility of four microcapsules was investigated by soil thin layerchromatography. The maximum retentions were measured with impregnation on thecabbage leaves. The efficiency period of four microcapsules were measured withspraying on cabbage leaves for3rdinstar larvae of Spodoptera exigua Hübner. Theindoor toxicity of3rdinstar larvae was studied with the leaves dipping method. Themain contents are as the following aspects:1.The urea-formaldehyde resin of beta-cypermethrin microcapsules were preparedby the in-situ polymerization.30%urea-formaldehyde resin prepolymer was preparedwith Urea and Formaldehyde as raw materials, PAAS as dispersing agent and SMAas emulsifying agent. The different particle-size microcapsules were prepared whenthe ratio of PASS/SMA uncharged and regulated the amount of them. The melamine-formaldehyde resins of beta-cypermethrin microcapsules were preparedwith Melamine and Formaldehyde as raw materials and other conditions as theurea-formaldehyde resin microcapsules. These microcapsules have followed advantages such as D₅₀over3⁵μm,the encapsulation efficiency over90%,the drug loadingrate over80%.And the capsule-shaped of these microcapsules was spherical.Thepolyurea of beta-cypermethrin microcapsules were prepared with MDI as raw material,sodium lignosulfonate as dispersing agent and OP-10as emulsifier by the interfacialpolycondensation. The polyurethane beta-cypermethrin microcapsules were preparedwith MDI and PEG400as raw materials and other conditions as the polyureamicrocapsules. The different particle-size microcapsules were prepared when3of themass ratio of sodium lignosulfonate/OP-10uncharged and regulated the amount ofthem. These microcapsules have followed advantages such as D₅₀over3⁵μm,theencapsulation efficiency over80%,the drug loading rate over70%.And thecapsule-shaped of these microcapsules was spherical.2.Release kinetics study shows that the releasing of four microcapsules withdimethylbenzene as organic solvent could be described by the first order kineticsequation.3.The difference photolysis study as follows: Under UV light, the photolysis ratewere ranked as beta-cypermethrin technical, EC, microcapsule suspensions whichwere polyurethane, polyurea, melamine-formaldehyde resin and urea-formaldehyderesin used as the wall materials, and the half-lives were2.3,9.4,20.7,39.0,45.8and51.9h, respectively. Their half-lives were followed by5.8,5.9,6.9,6.7,12.9and17.3dunder the natural light. The photodegradation rate of CS was significantly lower thantechnical and EC, so its efficiency period would be extended. The differencedegradation study as follows: the degradations were ranked asmelamine-formaldehyde resin, polyurethane, urea-formaldehyde resin, and polyureaunder UV light for60d. And the vale from high to low was1.15%,0.19%,0.17%, and0.06%. Followed the time, the color of the polyurethane and the polyurea becamedeeper, and changed from buff to dark yellow; both the urea-formaldehyde resin andthe melamine-formaldehyde resin were white and had little change. 4.The migration studying as follows: using the same particle-size of CS and wateras developing solvent, the migration rate of beta-cypermethrin CS ranked as polyurea,polyurethane, melamine-formaldehyde resin, urea-formaldehyde resin, the rate ofdifferent particle-size of the CS was increased along with the increasing of particle-size.5.The maximum retention was studied on the cabbage leaves for four microcapsu-les. The result as follows: the maximum retentions were ranked as polyurethane,melamine-formaldehyde resin, polyurea, urea-formaldehyde resin which made as wallmaterials of microcapsule suspensions. And the vale from high to low was11.85mg·cm^-2,11.02mg·cm^-2,10.12mg·cm^-2,9.33mg·cm^-2.6.The efficiency period of four microcapsules were measured with spraying oncabbage leaves for3rdinstar larvae of Spodoptera exigua Hübner.Result indicated thattheir efficiency period would be extended by microencapsulating and theurea-formaldehyde microcapsules were the longest, followed with polyurea,melamine-formaldehyde resin, Urea-formaldehyde. So the polyurethanes were viewedas better wall materials in spraying on the stems and leaves. Beta-cypermethrin iseasily to photolysis and hydrolysis. It would have a longer efficiency period and highsecurity when be changed to water-based formulation by microencapsulating.7. The virulence for four wall materials microcapsules and EC on3rdinstar larvaeof Spodoptera exigua Hübner by leaf dipping method. The virulence’s were ranked aspolyurethane, polyurea, melamine-formaldehyde resin, urea-formaldehyde and EC onSpodoptera exigua Hübner which were Beijing Spodoptera exigua from48h to72h.The virulence in48h less than72h for CS. The virulence of EC was not significa-nt difference.