The Mechanism of the Loss of Copper from Cotton Fabric During Actinic Breakdown under Conditions of Wetting

Abstract

The factors responsible for the rapid loss of most fungicidal compounds from treated cotton fabric subjected to weathering outdoors include water-solubility of the compound. actinic breakdown of the compound or the substrate, reaction between compound and substrate, migration of compound, and mechanical loss of compound. Experiments designed to study the above factors are described in which bleached cotton fabric untreated and treated with copper carbonate was subjected to the action of continuous water leaching and to intermittent leaching and drying; the loss of copper and amount of chemical deterioration were determined. Intermittent leaching and drying increased both breakdown and loss of copper. In experiments in which similar samples were exposed to light containing moderate amounts of radiation in the region of 3000-4000 Å the presence of copper was found to enhance the deterioration. Loss of copper caused by water leaching following ex posure, or by intermittent exposure and leaching, increased with increasing exposure to light. Exposure of similar samples to light with intermittent dampening with water, with or without drying prior to re-exposure, increased the tendency of the copper to be removed by subsequent water leaching. There is evidence of marked migration of copper in these experiments. the loss of copper noted in these experiments appears to involve solubilization of the copper by the oxidation products of the cotton cellulose.