Preparation and properties of lambda-cyhalothrin/polyurethane drug-loaded nanoemulsions

Conventional pesticide formulations are usually used inefficiently due to loss and poor foliage adhesion, which results in a large waste of resources and serious environmental pollution. In order to prolong the foliar pesticide retention and release time, using biodegradable castor-oil based polyurethane (CO-PU) as a carrier, lambda-cyhalothrin/CO-PU (LC/CO-PU) nanoemulsions were prepared via an in situ soap-free phase inverse emulsification technique and their properties were investigated. Results showed that the LC/CO-PU nanoemulsions had a good water dispersion and the drug-loaded nanoparticles (NPs) were uniform spheres with diameters of less than 80 nm. The LC physically encapsulated in the CO-PU carrier was in an amorphous state, and the maximum of the LC loading capacity was around 40 wt% with a high encapsulation efficiency of more than 85%. Compared with commercial LC formulations, the LC/CO-PU nanoemulsions exhibited a sustained and controlled-release property, which could be adjusted by the LC loading capacity and temperature. The foliage adhesion of the LC/CO-PU nanoemulsions was much better than that of the commercial LC formulations due to the low surface tension, larger chain mobility of the LC/CO-PU systems as well as hydrogen-bond interactions between the polyurethane and foliar surface, which was of great significance to achieve the efficient use of pesticides. A new lambda-cyhalothrin/castor oil-based polyurethane formulation with controlled-release behavior and good foliage adhesion properties is prepared.