Effects of softeners and laundering on the handle of knitted PLA filament fabrics

We have studied the effects of softeners and repeated laundering on the handle of knitted fabrics constructed from poly(lactic acid) (PLA) filament yarns derived from corn-starch. The fabrics were assessed: a) subjectively, via a panel of volunteers, in terms of their perceived softness and ‘scroopiness’; and b) objectively, using a Kawabata Evaluation System for Fabrics (KES-F), in terms of their low-stress mechanical properties. The study employed two fabric variants and a range of commercial softeners in an attempt to determine the combination that would provide optimal handle and durability to laundering. We found the standard KES-F parameters B, 2HB, G, 2HG, and SMD to be generally well-correlated with the subjective assessment of softness and scroopiness. Although repeated laundering reduced somewhat the beneficial effects of the softeners, this deterioration was not severe, and we were able to identify specific formulations that can provide good handle coupled with acceptable durability. The fabric handle was seen to be influenced by the chemical nature of the softening agent, the type of emulsion employed and the degree of hydrophobicity (assessed in terms of wettability); on the other hand, the ionicity of the softener appeared not to play a significant role.