Preparation And Performance Characteristic Of Lambda-cyhalothrin Microcapsule Fabricated With 1,2-diaminopropane Modified Novolac Epoxy Resin

As we all known that pesticide microcapsules have many advantages such as prolong controlling effect,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 research of the new wall material about microcapsules.We aim to fabricate lambda-cyhalothrin-loaded microcapsules with diamine modified novolac-epoxy resin as wall material and investigate the influences of novolac-epoxy resin amount,the kinds of polyamine,emulsifier type,novolac epoxy resin and shearing rate on their properties such as basic physicochemical parameters,release properties and application properties.The surface morphology of microcapsule was observed via scanning electron and optical microscope.Infrared spectrometer was used to analyze the structure of the polymer.Gas chromatography was used to analyze the loading capacities,encapsulation efficiency and release properties of the microcapsules.A particle size distribution machine was used to measure the average diameter and size distribution of the microcapsules.The insecticidal activities of the microcapsules were determined using leaf dipping method.The main contents are as the following aspects:1.Lambda-cyhalothrin microcapsules were prepared by interfacial polymerization with diamine modified novolac-epoxy resin as wall material.The obtained microcapsules were regular spherical particles,smooth surface without holes and tiny wrinkles under optimized conditions（10%solvent naphtha as lipophilic solvent,F51-novolac epoxy resin as lipophilic monomer,1,2-diaminopropane as monomer in aqueous phase,OP-10 and sodium lignosulfonate as wetting-dispersing agents）.The range of average particle size of the obtained samples was between 2.76 and 35.62μm;encapsulation efficiency was higher than89%and the loading capacity was in the range of between 39.38 and 43.97%.The microcapsules released fast in the first 15 min and reached a cumulative release amount of78.01%at 15 min;then they released much slower between time nodes of 15 min and 240min,with cumulative release amount reached 97.04%at 240 min.2.With the increasing of the epoxy groups of novolac-epoxy resin,the crosslinking density of polymer also increased and release rate became slowly,they cumulative release amount reduced from 83.59%（F44）to 70.49%（F51）on 30 min,they cumulative release amount reached to 54.16%,60.17%,66.25%and 73.01%;loading capacities were more than 90%and encapsulation efficiency all reached about 40%,the treatments had no difference.3.With the increasing of the content of novolac-epoxy resin（3%,4%,5%and 6%）,average diameter of the microcapsules respectively at 21.33,24.77,29.65 and 35.62μm;the loading capacity declined from 43.97%to 39.38%;The microcapsules reached cumulative release amounts of 54.16%,60.17%,66.25%and 73.01%on 15 min,the cumulative release amounts of microcapsules were reached 97.04%,95.74%,92.40%and 88.87%on 240 min;the encapsulation efficiency were closed to 90%and not vary significantly.4.The results also showed that with the shearing rate increased from 3000 r/min to12000 r/min,the average diameter of the microcapsules decreased from 23.15μm to 2.76μm.The release rate increased with the decreased of the average diameter,the cumulative release amounts of microcapsules increased from 12.21%to 62.01%on 1 min,the cumulative release amounts were reached at 91.55%,94.38%,96.75%and 98.59%on 240min.5.We used leaf-dip method to measure the lambda-cyhalothrin-loaded microcapsules of four different particle sizes（2.78μm、5.19μm、11.86μm and 23.15μm）and emulsifiable concentrate against agrotis ypsilon.The results showed that the toxicities(with the LC₅₀ of7.19 mg/L、13.65 mg/L、27.24 mg/L and 32.29 mg/L)were increased with the download of the particle sizes,and the toxicities of microcapsules all below emulsifiable concentrate(LC₅₀ was 3.94 mg/L).The four different particle sizes（2.78μm、5.19μm、11.86μm and 23.15μm）lambda-cyhalothrin-loaded microcapsules also displayed favorable insecticidal activity against Agrotis ypsilon(with the LC₅₀ of 7.19 mg/L、13.65 mg/L、27.24 mg/L and 32.29mg/L)although they showed no significant difference compared with that of emulsifiable concentrate treatment(LC₅₀ was 3.94 mg L^-1).