Role of polyoxyethylene ethers nonionic surfactants in leather dyeing: Investigation by spectrophotometry and dynamic light scattering method

Abstract

The interactions among polyoxyethylene ethers nonionic surfactants (C18POEn), C.I. Direct black 19 and gelatin were studied by spectrophotometry. Combin ing reflectance measurements, the effect of C18POEn and its adding order on leather dyeing kinetics and surface color were analyzed. Moreover, particle sizes in C18POEn solutions with C.I. Direct black 19 or gelatin were estimated by dynamic light scattering method. There were complexes formed by hydrogen bonds and hydrophobic interactions among C18POEn, C.I. Direct black 19 and gelatin. With C18POEn the dyeing process was slowed down; the uniformity and shade of surface color were improved. Furthermore, C18POE n added together with dye can bring the best levelling effect. Particle size results suggest that C18POE n is prone to interact with dye, not with gelatin. All these results verify that the levelling effect of polyoxyethylene ethers nonionic surfactants depend on the interactions between surfactants and dyes. The study shall facilitate the use of advanced analytic techniques for understanding leather dyeing process.