Detection of ammonia mercerization in cotton textiles

Abstract

Cotton textiles are mercerized with anhydrous ammonia liquefied at ca. − 33 °C to improve their mechanical performance, appearance, and handle. Similar effects may also be achieved with NaOH mercerization, but goods mercerized with liquid ammonia (L-NH₃) are judged qualitatively better (e.g., softer hand) and thus command a greater price. Therefore, it is of interest to be able to test and confirm whether cotton textiles labeled as L-NH₃ treated are indeed so. Building on previous work, we report on tests in collaboration with a process house on identifying ammonia-mercerized fabrics from a pool of cotton textiles treated with L-NH₃, NaOH, neither, or both––using FTIR-ATR spectroscopy. It is based on detecting the change in crystal lattice structure from type I (native cellulose) to type II (after NaOH mercerization) or type III (after ammonia mercerization). We could consistently differentiate the ammonia-mercerized fabrics from the untreated and those mercerized with NaOH, but the latter could not be differentiated from fabrics mercerized with both. It was also possible to detect evidence of ammonia mercerization in 4- and 14-year-old samples.

Graphical abstract