Lambda-cyhalothrin microcapsule prepared with 1,2-diaminopropane modified novolac epoxy resin by using interfacial polymerization

lambda-cyhalothrin-loaded microcapsules were prepared with diamine modified novolac-epoxy resin as wall material. The influences of novolac-epoxy resin amount and shearing rate on their properties, such as basic physicochemical parameters, release profiles and application properties were also investigated. The lambda-cyhalothrin microcapsules were prepared by interfacial polymerization of an oil-in-water emulsion which contained an oil-soluble novolac epoxy resin and water-soluble 1,2-diaminopropane. The microcapsules obtained were characterized by optical microscope and scanning electron microscopy. The structure of the polymer was analyzed using the infrared spectrometer. The loading capacity, encapsulation efficiency, and the release performance were analyzed using gas chromatography. The average particle size and distribution of microcapsules were detected by a laser particle size analyzer. The insecticidal activity of lambda-cyhalothrin microcapsules was determined using leaf-dipping method. The microcapsules were regular spherical particles, all of which displayed smooth surface without holes and accompanied with tiny wrinkles. With the increase of the content of novolac-epoxy resin, the average diameter of the microcapsules increased, the loading capacity declined, the release rate decreased and the encapsulation efficiency did not change significantly. The results also showed that the average diameter of the microcapsules decreased and the release rate increased with the shearing rate. As for the microcapsules prepared under the optimal conditions, the average particle size of the sample was 21.33 μm, encapsulation efficiency was 91.04% and the loading capacity was 43.97%. The microcapsules released fast in the first 15 min and reached a cumulative release rate of 78.01% in the first 15 min. Then they released much slower in the period between 15 min and 240 min, with cumulative release rate of 97.04% in the first 240 min. The lambda-cyhalothrin-loaded microcapsules with different particle sizes (2.78, 5.19, 11.86 and 23.15 μm) also displayed favorable insecticidal activities against Agrotis ypsilon (with the LC50 of 16.44, 23.33, 29.36 and 37.57 mg/L), although they had slightly lower toxicity compared with that of emulsifiable concentrate treatment (LC50 was 10.41 mg/L). Microcapsules fabricated with diamine modified novolac-epoxy resin exhibited rapid effectiveness and tunable bioactivity which make them potential candidates in pesticide formulations, especially microcapsules.