Colloids and Surfaces A: Physicochem. Eng. Aspects 479 (2015) 52–59 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects j ourna l h om epa ge: www.elsevier.com/locate/colsurfa Cationic ester-containing gemini surfactants as retarders in acrylic dyeing Mousa Sadeghi-Kiakhani a,∗ , Ali Reza Tehrani-Bagha b a Institute for Color Science and Technology, Department of Organic Colorants, Tehran, Iran b Department of Chemical and Petroleum Engineering, American University of Beirut (AUB), Beirut, Lebanon h i g h l i g h t s • Three cationic gemini surfactants were used as retarders in acrylic dye- ing. • The kinetic of acrylic dyeing was studied using various empirical mod- els. • The surfactants reduced the rate of cationic dye adsorption. • The rate of dye adsorption was increased by temperature. • The ester-containing geminis showed much weaker blocking effect. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 25 December 2014 Received in revised form 20 March 2015 Accepted 24 March 2015 Available online 1 April 2015 Keywords: Gemini cationic surfactant Ester bond Acrylic dyeing Dye adsorption Cationic dye a b s t r a c t Two ester-containing cationic gemini surfactants (esterquat and betainester types) and one stable cationic gemini surfactant with the same spacer length between the two quaternary head groups were investigated as retarding agents in acrylic dyeing with a cationic dye. The effects of surfactant concen- tration, time, and temperature were studied on cationic dye adsorption onto acrylic fibers. The results indicated that the presence of ester bond in alkyl tails of cationic gemini surfactants has an important role on the retarding action of dyeing process and it reduces the blocking effect. The dye adsorption kinetic at various surfactant concentrations and temperatures was studied by using different empirical models. The cationic dye adsorption on acrylic fiber showed a very good correlation with the modified Cegarra-Puente empirical model. According to the obtained activation energy values, the dye diffusion into the fiber depends significantly on the chemical structure of the used gemini cationic surfactants and their concentrations. © 2015 Elsevier B.V. All rights reserved. ∗ Corresponding author. Tel.: +98 21 22969774; fax: +98 21 22969774. E-mail address: sadeghi-mo@icrc.ac.ir (M. Sadeghi-Kiakhani). 1. Introduction Acrylic fiber is one of the most popular synthetic fibers and its annual production was ∼2.2 million tons/year in 2010 [1,2]. This fiber has extensive applications in apparel as well as in various industrial sectors owing to its outstanding physical and chemi- cal properties such as high strength and good abrasion and insect http://dx.doi.org/10.1016/j.colsurfa.2015.03.030 0927-7757/© 2015 Elsevier B.V. All rights reserved.