Controlled release granules

Two types of carbofuran formulations were tested, a gypsum-based roll-compacted granule manufactured by Union Carbide (Res. Triangle Pk., N. Carolina) and a proprietary controlled-release granule manufactured by Sierra Chem. 

Controlled-release formulations extended the persistence of carbofuran in soils exhibiting enhanced biodegradation. Owing to the comparatively low susceptibility of CRW larvae to carbofuran, and the apparently very slow release of carbofuran from the Sierra controlled-release granules, carbofuran efficacy at normal... 

Matrix Particles. Small particles based on a matrix can range in size from powders (microparticles) to granules (fine to macrogranules) to pellets (43). Microspheres can be considered as the matrix equivalent to microcapsules. Most controlled release granules are matrix-based, although some have a solid core or reservoir of pesticide (with a coating). 

In addition to improved delivery and replacing persistent organochlorine pesticides with nonpersistent compounds, controlled release granules also provide reduced toxicity of the product. For example, the acute oral toxicities of these granules are much reduced (giving higher LD50 values) compared to unformulated or conventional sprayable formulations, as shown in Table 3. 

So, the wax was melted but DT was not melted in these processes, because the melting point of DT was higher than that of the wax. The extruded product was cooled to room temperature. After a disintegration and sieving process, the controlled release granule (CR-Gr) was obtained. 

Release Properties of Controlled Release Granule I. Effect of kind of wax... 

Mt is the cummulative concentration of released DT at time t (hr), k is the release rate coefficient, and C is the intercept. When the results in the 2nd step after ten minutes were plotted by the equation, a very good linear relationship, in which the coefficient of correlation was almost one, was obtained (Figure 3). Accordingly, the DT release profile of the controlled release granule was considered as simple diffusion. 

We developed a controlled release granule of DT containing a certain wax, and its release properties agreed with the Higuchi diffusion model. There were four factors which have an effect on the DT release properties. 

The biodegradability of the formulating material is em important aspect of controlled release for environmental applications. Several synthetic and natural polymers used for formulating granules are biodegradable. The delivery of bioactives from controlled-release granules can be enhanced by inclusion ofbiosurlactants. 

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