Fabric softeners deposition mechanism

Fabric softeners remedy these degradations and improve the feel by coating the fibers with a protective film of fatty material that reconstitutes the finish, maintains the microfibrils close to the fibers [23], masks fiber alterations, and covers the mineral deposits. Hence, the main mechanism for fabric softening is fiber lubrication. 

Softener deposition is drastically affected by anionic surfactants such as linear alkylbenzene sulfonate (LAS) or sodium lauryl sulfate (SLS) because of the immediate formation of water-insoluble complexes. For instance, if increasing amounts of SLS are added to a softener dispersion, DHTDMAC deposition is nearly quantitative until both concentrations are equal. The amount of softener on the fabric always corresponds to the concentrations of free softener and of catanionic complex. It seems likely that the complex is held on cotton by mechanical entrapment in the cotton fibers [72], Once the SLS concentration exceeds that of the softener, the complex is increasingly solubilized by the surfactant excess and deposits less and less [72,92,108],... 

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