Effect of inert fillers on diffusion and controlled release of penetrant in polymer matrices

Abstract

This study investigates the characteristics of leaching into a solvent of an active used as termiticide, Bifenthrin 1 (a synthetic pyrethroid) entrapped in polymer, and the effect of layered silicates on this diffusion. Two contrasting solvents, water and acetone, were used to understand this phenomenon; the active is soluble in acetone but has very low solubility in water. The data are used to understand the migration characteristics of Bifenthrin when encapsulated in polyurethane to form a termite barrier. The absorption characteristics of Bifenthrin in polyethylene were also studied for comparison. Bifenthrinpolyurethane blends containing 0, 0.5, and 5% of layered silicates were prepared and monitored for the release of Bifenthrin. Using the time-concentration dependence of the active in polymer, diffusion coefficients of Bifenthrin from the polymer were inferred assuming Fickian diffusion. The presence of silicates had no significant effect on the diffusion behavior.

The molecular arrangement of Bifenthrin® in ether based polyurethane: Designing a synthetic termite barrier

“…Termiticides have been found to diffuse from polymeric materials in soil and dry conditions 3. In a previous study, Bifenthrin® was shown to diffuse slowly from the EPU in aqueous media 7. However, the XPS data above indicated that the active fluorine containing group of Bifenthrin® was preferentially on the surface of the EPU.…”

“…In addition, the chemical structure of polyurethanes may permit interactions between the host polymer and the active, which would retain the active within the barrier for long periods of time. In a previous paper,7 it has been shown that high levels of Bifenthrin® can be incorporated in the EPU and that the diffusion rates of the active into water from the impregnated polymer are very slow. These results indicate the possibility of extending the life of environmentally friendly pesticides using this concept and limiting the release of actives into the environment.…”

“…Substantial diffusion of lambda cyhalothrin has been detected in polyethylene systems, resulting in termite repellence and mortality 14. It has been shown previously that the diffusion of the active from EPU is quite low and appears to be controlled,7 but it is not known if this is sufficient to kill or repel the targeting termite pest. This aspect is addressed in this work.…”