Estudio de la Liberación Controlada de Plaguicidas Incorporados en Hidrogeles de Acido Itacónico
Fecha
2004
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Universidad del País Vasco (España)
Resumen
Resumen. Los hidrogeles presentan características estructurales de gran interés por sus aplicaciones en la medicina y en el campo de la agricultura. Este estudio presenta los resultados obtenidos en el estudio de la liberación controlada del plaguicida conocido como bromacil (5-bromo-3-secbutil- 6-metiluracil, C9H13BrN2O2, cc. herbicida 976, Hyvar X, Hyvarex, bromax, borea), en hidrogeles del ácido itacónico. Estos materiales fueron sintetizados a partir de la
copolimerización del ácido itacónico y acrilamida en presencia de diferentes porcentajes de N,Nmetilenbisacrilamida (MBA) como agente entrecruzante. La liberación controlada de este plaguicida se realizó en un medio acuoso, a pH neutro, a 23°C. El bromacil se liberó completamente a los 4 días, mostrando diferencias poco significativas entre los hidrogeles preparados con distintas cantidades de MBA (1, 2, 5 y 5%). Sin embargo, el material que
contenía 10 % del agente entrecruzante mostró la mayor velocidad de liberación del plaguicida. Asimismo, la liberación observada en la mayoría de los materiales estudiados, siguió el modelo cinético descrito por Stastna. Esto indica que el mecanismo de liberación del bromacil para las formulaciones con distinta concentración de MBA, está gobernada por difusión y la interacción entre el polímero y el bromacil. Finalmente, los resultados en la caracterización mediante termogravimetría indican que la transformación del material fue completa y que no quedaron monómeros que pudieran producir problemas de contaminación. Se observó además, que la presencia de bromacil disminuyó la estabilidad térmica de los hidrogeles.
Abstract. Hydrogels present structural characteristics of great interest due to their applications in medicine and in the field of agriculture. This study presents the results obtained in the study of the controlled release of the pesticide known as bromacil (5-bromo-3-secbutyl- 6-methyluracil, C9H13BrN2O2, cc. herbicide 976, Hyvar X, Hyvarex, bromax, borea), in hydrogels of itaconic acid. These materials were synthesized from the copolymerization of itaconic acid and acrylamide in the presence of different percentages of N,Nmethylenebisacrylamide (MBA) as a cross-linking agent. The controlled release of this pesticide was carried out in an aqueous medium, at neutral pH, at 23°C. Bromacil was completely released after 4 days, showing insignificant differences between the hydrogels prepared with different amounts of MBA (1, 2, 5 and 5%). However, the material containing 10% of the cross-linking agent showed the highest release rate of the pesticide. Likewise, the release observed in most of the materials studied followed the kinetic model described by Stastna. This indicates that the release mechanism of bromacil for formulations with different concentrations of MBA is governed by diffusion and the interaction between the polymer and bromacil. Finally, the results of the characterization using thermogravimetry indicate that the transformation of the material was complete and that there were no monomers left that could cause contamination problems. It was also observed that the presence of bromacil decreased the thermal stability of the hydrogels.
Abstract. Hydrogels present structural characteristics of great interest due to their applications in medicine and in the field of agriculture. This study presents the results obtained in the study of the controlled release of the pesticide known as bromacil (5-bromo-3-secbutyl- 6-methyluracil, C9H13BrN2O2, cc. herbicide 976, Hyvar X, Hyvarex, bromax, borea), in hydrogels of itaconic acid. These materials were synthesized from the copolymerization of itaconic acid and acrylamide in the presence of different percentages of N,Nmethylenebisacrylamide (MBA) as a cross-linking agent. The controlled release of this pesticide was carried out in an aqueous medium, at neutral pH, at 23°C. Bromacil was completely released after 4 days, showing insignificant differences between the hydrogels prepared with different amounts of MBA (1, 2, 5 and 5%). However, the material containing 10% of the cross-linking agent showed the highest release rate of the pesticide. Likewise, the release observed in most of the materials studied followed the kinetic model described by Stastna. This indicates that the release mechanism of bromacil for formulations with different concentrations of MBA is governed by diffusion and the interaction between the polymer and bromacil. Finally, the results of the characterization using thermogravimetry indicate that the transformation of the material was complete and that there were no monomers left that could cause contamination problems. It was also observed that the presence of bromacil decreased the thermal stability of the hydrogels.
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PLAGUICIDAS, HIDROGELES, ACIDO ITACÓNICO, PESTICIDES, HYDROGELS, ITACONIC ACID