Housewives are familiar with the phenomenon and children despise it: after washing and subsequent drying on the line or drying rack, textiles – particularly cotton ones – do not feel soft and fluffy, but stiff and hard. Experts refer to this as “dry stiffness,” which forms in still air. This phenomenon is caused by electrostatic hydrogen bonds between the cellulose fibers.
To make laundry as “heavenly soft” as promised in advertisements, we use so-called fabric softeners. Their main active ingredients are cationic surfactants. Thanks to their positively charged functional groups, they absorb onto the negatively charged textile fibers and are held there by electrostatic interaction. Alongside their positive charge, the cationic surfactants that are used as fabric softeners also carry long hydrocarbon chains, similar to the ones in fats. These lipid chains ensure enhanced lubrication between the fibers and between the surface of the skin and the fabric. This makes the textiles that are enhanced with these fabric softeners feel soft.