Effect of pH and the Role of N-Methylol Hydrolysis in Formaldehyde Release from Durable Press Fabric

Abstract

A series of experiments are reported that demonstrate the effects of fabric pH on the release of formaldehyde from fabrics treated for durable press with formaldehyde- containing resins. Release, as measured by the AATCC sealed jar procedure, is a minimum in the neutral pH range; it increases as residual fabric acidity increases because of increased crosslink (C—O) hydrolysis, which produces N-methylol groups that hydrolyze in turn to form formaldehyde; release increases to even a greater extent as the fabric becomes increasingly alkaline because of the hydrolytic sensitivity of the C—N bond in pendant N-methylol groups at high pH. Similar pH effects are observed with methylated ("capped") resin. To determine the degree to which formaldehyde release results from N-methylol hydrolysis, a series of fabrics containing pendant N-methylol groups over a considerable range of concentrations were analyzed for N-methylol content before and after the AATCC measurement of formaldehyde release. In general, release is somewhat higher than expected from the decrease in N-methylol content. This suggests that other mechanisms, for example, release of free formaldehyde initially present in the fabric and hydrolysis of crosslinks to form additional pendant N-methylol, contribute to the formation and release of formaldehyde from these treated fabrics.