SYMPOSIA PAPER Published: 01 January 1998

Pesticide Stability Versus Clay Carrier Surface Acidity


Clay granules are well known as carriers for a broad range of pesticides including various insecticides, herbicides and fungicides. Although they generally function quite well in this applications, formulations utilizing chemically sensitive pesticides must often be augmented with organic deactivators such as dipropylene glycol, polypropylene glycol, etc. in order to stabilize the system against degradation of the active ingredient. The present paper reports on the use of clay carriers which have been processed in a new way that significantly enhances their chemical inertness by modifying surface activity (i.e.surface acidity). This objective has been realized without compromising hardness or liquid holding capacity. Utilizing these materials, we have attempted to draw a correlation between pesticide stability (measured as pKa value of first hydrolysis decomposition products) and carrier surface acidity. A number of well-known pesticide molecules chosen from the phosphate ester and thiocarbamate classes have been used to illustrate these correlations.

Author Information

Taylor, DR
Oil-Dri Corporation of American, Vernon Hills, IL
Stein, J
Oil-Dri Corporation of American, Vernon Hills, IL
Svidovsky, N
Oil-Dri Corporation of American, Vernon Hills, IL
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Developed by Committee: E35
Pages: 215–227
DOI: 10.1520/STP14167S
ISBN-EB: 978-0-8031-5392-9
ISBN-13: 978-0-8031-2491-2