Microencapsulation of some agricultural chemicals with polyurethane used in agriculture

In this study, herbicide (pendimethalin) and insecticide (lambda cyhalothrin) used in agricultural applications were microencapsulated with polyurethaneurea. The dimensions of the microcapsules, wall thicknesses, yields, duration of active substance release were investigated and the insecticide was applied to the 2-point red spider on the mint plant. The polyurethaneurea resin, the main component of the capsule shell, was synthesized at an isocyanate / polyalcohol / polyamine molar ratio (5.4 / 5.5-3.0 / 1.5-3.9) at 55 oC and 180 minutes. Pendimethalin and lambda-cyhalothrin which are commonly used in agricultural pesticides industry have been determined to be stable by four different emulsifying (O/W, oil/water) agents in water. The emulsified mixture was reacted with toluene diisocyanate (TDI), different glycols, hexamethylene diamine (HMDA) and hydrazine monohydrate (HYD) to form microcapsules in a micron size. Characterization of the obtained capsules In FT-IR spectroscopy, the size and stability of the emulsified droplets were examined by optical light microscopy, the dimensions and the wall thickness of the microcapsules by SEM (scanning electron microscopy), and the thermal decay of the microcapsules by TGA (thermogravimetric analysis). The maximum yield of microcapsules were 89.1 % in the pendimethalin and 85.5 % in the lambda-cyhalothrin, the thickness of the capsule wall was 335.6-1479 nm. The release percentages of the microcapsules in alcohol-water and UV-irradiated for 4 hours at 20 °C were found to be minimum 28.52 % and maximum 40.81 % for insecticide, and minimum 30.79 % and maximum 40.12 % for the herbicide, respectively. Insecticides containing microcapsules were observed to be effective for two month against to 2 point red spider when applied to mint plants.