Retention of some non‐mercurial fungicides in paint films

Abstract

The fungicides, 3,5‐dimethyltetrahydro‐1,3,5‐thiadiazine‐2‐thione (DTTT) and 4‐tolyldiiodomethylsulphone (TDMS) have been prepared labelled with 14C and incorporated into polyvinylacetate emulsion (PVA), styrene/acrylic emulsion (acrylic) or alkyd gloss (alkyd) paints. Test plates prepared from these paints have been exposed in both tropical and temperate conditions and losses of fungicides have been followed radiometrically. In outdoor conditions, DTTT is rapidly lost from all the paints. Indoors, DTTT is retained well (50% after 150 days) only by alkyd paint. TDMS is well retained in indoor conditions by all the paints. Outdoors however, retention in PVA and acrylic films is less than 50% after 150 days and is poorer in tropical conditions. About 90% of the TDMS is retained in alkyd films for an indefinite period in temperate conditions: in tropical conditions, 80% is retained after 150 days. Comparisons of losses from paint films of mercurial and non‐mercurial fungicides show that TDMS is a satisfactory substitute for the more commonly used mercurials.