The influence of alkali pretreatments in lyocell resin finishing—Changes in fiber accessibility to crosslinker and catalyst

The aim of the work was to examine reasons behind the detrimental effects of alkali pretreatments on resin finishing of lyocell, a regenerated cellulosic. The accessibility of DMDHEU and MgCl2, which are typically used crosslinker and catalyst in resin finishing treatments of cellulosics, were determined in lyocell fibers treated with 0–8 mol/l alkali (NaOH and KOH). The accessibility of MgCl2 was found to exceed that of DMDHEU in the original, untreated fibers. The differences were further enhanced on alkali treatments; attributed to a reduction of the pore size in fibers after alkali treatments. The changes to pore size, and the resultant rise in differences between catalyst and crosslinker accessibility, appeared related to fiber swelling extents during alkali treatments. The widening of differences between crosslinker and catalyst accessibility in alkali treated lyocell, is believed responsible for the detrimental effect of alkali pretreatments on resin finishing of lyocell fabrics. e fibers, subjected to the same alkali treatments, did not exhibit a similar widening of differences between crosslinker and catalyst accessibility. Although, as in lyocell, the untreated viscose fibers exhibited greater accessibility to MgCl2 compared to DMDHEU, the alkali treatments did not change the levels of these differences. The lack of changes was attributed to the fact that viscose fibers do not exhibit pore size changes on alkali treatments.