Constructing slow-release formulations of herbicide metribuzin using its co-extrusion with biodegradable polyester poly-ε-caprolactone

Abstract

Different technologies to prepare long term pesticide forms include polymer coating, preparing composites and encapsulating pesticides in nanoparticles. A simple and low-cost method was proposed to obtain slow-release formulations by co-extrusion of a pesticide with a biodegradable polymer at a temperature above the melting points of both components. A herbicide metribuzin and low-melting polyester poly-ε-caprolactone were chosen for this work. Formulations containing 10%, 20%, and 40% herbicide were prepared. During 7 days of their exposition in water, it was released from 81% to 96% of initially loaded metribuzin; the highest release was detected for 40%-loaded forms. Biodegradation of the constructs and pesticide release were further studied in the model soil. Degradation rates of the specimens increased with an increase in pesticide content, from 9% to 20% over 14 weeks for the 10%/20%-loaded and the 40%-loaded specimens, respectively. The release of metribuzin reached, respectively, 37–38% and 55%. The herbicide content in soil was lower due to its partial degradation in soil; it reached 23–25% and 33%, respectively, from initially loaded into the polymer matrix. Release kinetics of metribuzin in water as in soil best fitted the First-order model. The used approach is promising for obtaining long-term release formulations for soil applications.

Keywords:

• Polycaprolactone
• herbicide
• pesticide
• long-term
• extrusion

Acknowledgments

The authors are thankful to Dr. Anna M. Shershneva (Siberian Federal University) for her assisting with modeling metribuzin release kinetics.

Additional information

Funding

This study was financially supported by Project “Agropreparations of the new generation: a strategy of construction and realization” (Agreement No 074-02-2018-328) in accordance with Resolution No 220 of the Government of the Russian Federation of April 9, 2010, “On measures designed to attract leading scientists to the Russian institutions of higher learning”.