SYMPOSIA PAPER Published: 01 January 1993

Use of Deactivators in Granular Clay Formulations


Clay-based granules find widespread use in pesticide formulations. Clays are absorptive, hard, easily handled and virtually dust-free. Formulation toxicity is often lessened and broadcast distribution less prone to drift than liquid spray formulations. Occasionally, though, a catalyzed pesticide degradation occurs. Presumably a clay has “active sites” that catalyze this degradation, particularly with phosphate ester insecticides. Clay suppliers have made great strides in lessening the catalytic activity of granules, but a deactivator is still often required in the formulation. These active sites are presumably Lewis acids, i.e., electron pair acceptors. Flooding the clay surfaces with an electron-rich compound covers the active sites and degradation no longer occurs. for this reason, oxygen and nitrogen containing compounds are often used. Historically, urea has been used with the chlorinated hydrocarbons. Today, glycols and their ethers are most often used. Data will be presented on the use of a variety of deactivators. Low molecular weight nitrogen-containing compounds such as ethanolamine are sometimes effective, also. Generally, propylene glycol is superior to ethylene glycol and their dimers are even more effective. Increasing polymer length, however, does little to improve observed pesticide stability over the dimers.

Author Information

Kallay, WB
Goss, GR
Stein, JA
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Developed by Committee: E35
Pages: 201–213
DOI: 10.1520/STP20195S
ISBN-EB: 978-0-8031-5221-2
ISBN-13: 978-0-8031-1439-5