Elucidation of Softening Mechanism in Rinse‐Cycle Fabric Softeners. Part 2: Uneven Adsorption—The Key Phenomenon to the Effect of Fabric Softeners

Abstract

We investigated the actual factor determining the softening effect of a fabric softener. The adsorption area of the softener on model cotton cloths and yarns was identified using bromophenol blue. There was almost no softener at the cross-points of the yarns in the cloth samples or in the inner part of the yarns. The softening performance was better when there was less softener at the cross-points of the yarns than when the yarns were evenly covered by the softener. Thus we conclude that the presence of softener at the cross-points of yarns is not a vital factor in the softening effect. In addition, more softener was found on the outer part of the yarn than the inner part, indicating gradation in the adsorption pattern of the softener. Thus, we propose that more softener is adsorbed on the exposed part of the yarn in a cloth, and the formation of a hydrogen-bonding network containing bound water is inhibited, thus softening the outer part of the yarn. However, the presence of a small amount of softener in the inner part of the yarn preserves the hydrogen-bonding network. Favorable elasticity, or bounce, of the yarns and cloth is realized when an appropriate amount of softener is used. Excess softener would reach the inner part of the yarn, reducing the diameter of the core part of the yarn, making the cloth appear wilted.

Design of eco-friendly fabric softeners: Structure, rheology and interaction with cellulose nanocrystals

“…Recent studies have correlated fabric frictional characteristics with smoothness and softness [10], while others have put forward that the friction between the human skin and fabrics has a more prominent role [11]. Following Igarashi et al the softening effect would come from the reduction of H-bonding between the bound water molecules and the cotton fibers [12,13]. Crutzen has suggested that hydrophobic interactions derived from the long alkyl chains of cationic surfactants are the primary driving force for adsorption [14], whereas Kumar et al proposed that the deposition process is electrostatically driven and that intact vesicles adsorb on cotton or viscose fibers [5,15].…”

Chemical–physical and dynamical–mechanical characterization on Spartium junceum L. cellulosic fiber treated with softener agents: a preliminary investigation

“…Since the fiber rigidity, and therefore its processability, is related to the cellulose crystallinity, the reduction of the crystalline portion, with consequent increase of the amorphous region, implies an increase of the fiber softness. A reduction of the fiber crystallinity can be obtained through the use of a softener, since, according to Igarashi et al, the softening effect of a fabric softener could be ascribed to the loss of some hydrogen bonds and Van der Waals interactions between the ordered polymeric chains, probably due to the “insertion” of softeners micelles 21 , 22 . On this basis, the measurement of the Crystallinity Index (CI) could represent an important parameter for assessing the fiber workability (fiber strength and elasticity).…”

“…One is that the softener molecules reduce the friction between adjacent fibers because they form a structured hydrophobic layer on the cellulose surface by exposing their alkyl tails toward the air after the drying process 21 . The other one is that the softeners prevent the formation of cross-linking bound water layers between the fibers during the drying process, which otherwise increases the fiber stiffness 21 , 22 .…”

A simple method of simultaneously endowing paper or fluff pulp with both high softness or appropriate fluffing properties and antimicrobial properties

“…Therefore, there is a clear need to develop special softening agents for this kind of papers or debonding agents for uff pulp board. In order to make the nal tissue products possess high antibacterial activity and at the same time create enough softness or appropriate burst strength, antibacterial agents (Hayashi et al 2019;Xu et al 2020) and softening/debonding agent (Igarashi et al 2016) are usually added together during the papermaking process. However, there are few reports on chemical additives which have both antibacterial and softening/debonding effects.…”