TAKAKO IGARASHI*, KOICHI NAKAMURA
*Corresponding author
KAO Corporation, Wakayama, Japan

Abstract

A conventional theory of the softening mechanism states that softening effect results from the increase in sliding between fibers and yarns. Our new theory explains the softening effect occurs by inhibiting cross-linkage between fibers by hydrogen bonds including non-freezing bound water. A softener plays two important roles: (1) Decrease of the meniscus force between fibers in drying process and preventing the decrease of distance between the fibers. (2) Softener inhibits the formation of cross-linkage made of bound-waters between fibers. Furthermore, softener causes uneven adsorption so that gradation of softener adsorption happens:more in outer parts, less in the inner parts. Thus, two different physical properties of the softer outer part and the harder inner part are the key factors to give the soft and bouncy feel of fabric in total.

Most consumers can relate to what happens when wet cotton rags are left to dry naturally (either after being squeezed by hands or left as it is): they become so hard as if the fabric has been glued. A fabric softener does an excellent job of reducing this type of hardness. In the early 1930s, research showed that cationic surfactants,which were at first developed to improve the water-fastness of direct dyes on cellulose also worked as softening agents (1). Cationic fabric softeners for consumer use were first introduced to the US market at around 1955 (2). Although the initial growth was not so high, the global market has since increased remarkably. Nowadays, the fabric softener is regarded as an essential item in many households. Fabric softeners on the market now further incorporate other functions, such as fragrance, wrinkle reduction, deodorisation, and antibacterial action. Nevertheless, the basic purpose of the fabric softener has not changed. The comfortable, bouncy feel of soft laundered fabrics makes our daily life more satisfying.

The fabric softener can easily and effectively improve the feel of laundered clothes and towels, especially those mad ...