Constructing Slow‐Release Metribuzin Formulations by Co‐extrusion of the Pesticide with Poly‐ε‐Caprolactone

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AbstractA simple and low‐cost method of obtaining slow‐release pesticide formulations is proposed by co‐extrusion of a herbicide metribuzin with a low‐melting biodegradable polyester poly‐ε‐caprolactone, at a temperature above the melting points of both components. Formulations containing 10%, 20%, and 40% herbicide are prepared. Metribuzin release in water during 7 days of exposition reached 81% from the formulations with the 10% loading and 96% from the specimens with the 40% herbicide loading. Biodegradation and pesticide release from the polymer constructs are studied in the model soil for 14 weeks. Degradation rates of the specimens increased with an increase in pesticide content: between 9% for the 10%‐loaded specimen and 20% for the 40%‐loaded specimen over 14 weeks. The release of metribuzin from the specimens with the 10–20% and 40% loadings reached 37–38% and 55%, respectively; thus, taking into account soil degradation of the herbicide, the herbicide content in soil reached 23–25% and 33%, respectively, of the initially loaded into the polymer matrix. The used approach is promising to obtain long‐term release formulations for soil application.