ELECTROKINETIC PHENOMENA OF 3-AMINOPROPYLTRIETHOXYSILANE-BASED COTTON FINISHING

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1 ELECTROKINETIC PHENOMENA OF 3-AMINOPROPYLTRIETHOXYSILANE-BASED COTTON FINISHING Ana Marija Grancarić 1, Giuseppe Rosace 2, Anita Tarbuk 1, Claudio Colleoni 2 1 University of Zagreb, Faculty of Textile Technology, Prilaz baruna Filipovića 28a, HR Zagreb, Croatia 2 University of Bergamo, Department of Engineering and Applied Sciences, Viale Marconi 5, Dalmine, Bergamo, Italy Corresponding author: Ana M. Grancarić; amgranca@ttf.hr Abstract The textiles are characterized by their inner and outer structure and functional groups. Specific adsorption of ions or dissociation of the surface groups in aqueous solution result in their surface charge. Changing the number of functional fiber surface groups, e.g. by blocking in dyeing and finishing processes, and their dissociation affect the distribution of surface charge, as well as the thickness and distribution of the electric double layer which results in different fabric electrokinetic phenomena [1-4]. Immersed in water (ph ) cotton fibers, like most textile fibers, are negatively charged in neutral and alkali aqueous solutions [5]. Therefore, the adsorption of textile auxiliaries, dyestuffs, optical brighteners and finishing agents is difficult due to repulsive forces. Cationisation, as an alternative method for improving dyestuff and surfactant adsorption, increases cotton zeta potential and changes the fiber surface charge [3, 4, 6-10]. Hashem et al. among others, studied the parameters of application of a non-polymeric cationic agent such as epihalohydrin; 2,3-epoxypropyl trimethyl ammonium chloride (EPTAC) and 3-chloro- 2-hydroxy-propyl trimethyl ammonium chloride (CHPTAC) by pad-roll and exhaustion methods, but as after-treatment only [8, 10]. On the other hand, Grancaric, Tarbuk et al. [3,4] introduced cationisation during mercerization processes, which resulted in new material. Recently, some commercial products for the same purpose have been developed. In the last years, the sol-gel technique has remarkably proved its exceptional potential regarding the functionalization of textile fabrics. Sol-gel solution leads to the formation of completely inorganic or hybrid (organic-inorganic) coatings that can be used to confer functional properties, such as antimicrobial, water repellency and flame retardancy [11]. In this study 3-Aminopropyltriethoxysilane (APTES) has been selected for the cationisation of cellulose due to the presence of amine groups into polysilane network. Materials and Methods Bleached cotton fabric (237 g/m 2 ) was generously supplied by Mascioni SPA, Varese, Italy. 3-Aminopropyltriethoxysilane (APTES, purity grade 98 %) and

2 tetraethylorthosilicate (TEOS, 99 %) were purchased from Sigma-Aldrich and used as sol-gel precursors. All chemicals were of analytical reagent grade and were used without any further purification. TEOS sol was prepared at M concentration. The amount of precursor was hydrolyzed in a deionized water solution by adding HCl (0.1 M) at 3 %v/v concentration. The reaction was carried out for 4 h under vigorous stirring at room temperature before application. Using the same procedure as mentioned above, three different APTES sols were synthesized at the concentrations of 0.2 M, 0.3 M and 0.4 M. All samples were treated with both TEOS and APTES solutions in a two-step procedure to realize a double layer coating. The treatments were carried out by a two-roll laboratory padder (Werner Mathis, Zurich, Switzerland) at nip pressure of 3 bar. All cotton fabrics (20 cm x 30 cm) underwent an impregnation with the solutions and afterward were squeezed to obtain a wetpick-up of about %. In detail, each cotton sample was firstly impregnated with M TEOS sol (used as primer for the 2 nd layer) and dried at 100 C for 5 min, and then at 150 C for 1.5 min. Successively, the fabric was treated with APTES solution at the suitable concentration. The sample was dried for another 5 min at 100 C and then cured at 170 C for 3 min in an electric laboratory oven. Electrokinetic (zeta, ζ) potential was measured by streaming potential method using Brookhaven-Paar Electrokinetic Analyzer with a stamp cell and calculated according to Helmholtz-Smoluchowsky equation [2]. It was investigated versus ph and versus cationic surfactant addition. Isoelectric Point (IEP) of Lyocell fibers was determined as well as Point of Zero Charge (PZC). Sigma-Aldrich products were used for PZC determination: N cetylpyridinium chloride (N-CPC) for anionic, and Sodium dodecyl sulphate (SDS) for cationic surfaces. Specific quantity of surface charge was calculated after back-titration method [3] applying Titrino 736 (Metrohm) and ionic surfactant electrode (Metrohm). N-CPC was used as cationic, and SDS as anionic surfactant solution. Results The results of electrokinetic phenomena zeta potential vs. ph and vs. ionic surfactant addition (N-CPC for anionic and SDS for cationic surfaces) in electrolyte M KCl, Isoelectric point (IEP), Point of zero charge (PZC) and Specific quantity of surface charge (q) were determined. For the purpose of this extended abstract IEP and ZP vs. ph are given in Table 1 and Figure 1.

3 Table 1. Zeta potential (ζ), and Isoelectric point (IEP) of cotton fabrics. Label Treatment ZP at ph 10 IEP COT-UT Bleached/untreated -12,3 < 2,5 * COT-0.2-APTES Treated with 0.2 M APTES -15,5 5,43 COT-0.3-APTES Treated with 0.3 M APTES -9,4 7,95 COT-0.4-APTES Treated with 0.4 M APTES -4,5 9,15 From the results can be seen that cotton fabrics show a negative charge in water solutions. The treatment of cellulose fibers with APTES leads to significant modification of fiber surface resulting in the reversal of charge. Due to the APTES coating the cationic character of amino groups can be observed. Applying the highest concentration of 0.4 M, the cotton surface shows almost positive zeta potential (-4.5 mv). From the results presented in Table 1 it can be seen that the isoelectric point (IEP) of untreated/bleached cotton has IEP < 2.5. The IEP moves to higher ph values as a result of 3-Aminopropyltriethoxysilane coating. It changes depending on the APTES concentration. For that reason, the lowest applied concentration of 0.2 M APTES results in IEP = 5.43, whilst for the 0.4 M APTES it is IEP = ZP [mv] ph COT-UT COT-0,2 APTES COT-0,3 APTES COT-0,4 APTES Figure 1. Zeta potential (ζ) of cotton fabrics vs. ph of electrolyte M KCl.

4 Conclusion The most important phase of textile finishing processes is adsorption of chemicals and substances on textile materials surface. Electrokinetic phenomena of APTES treated cotton fabrics indicate the possibility of its finishing and dyeing in the neutral medium since all coated surfaces have IEP >5.4. References [1] Jacobasch, Hanz Jorg, Akademie Verlag, Berlin (1984), pp [2] Grancarić, Ana Marija, Soljacic, Ivo; Pušić, Tanja; Biscan, Jasenka, Polimeri, 23 (2002) 6, pp , ISSN [3] Grancarić, Ana Marija; Tarbuk, Anita; Pušić, Tanja, Coloration technology. 121 (2005) 4, pp , ISSN [4] Grancarić, Ana Marija; Tarbuk, Anita; Dekanić, Tihana, Tekstil 53 (2004) 2, pp , ISSN [5] Tarbuk, Anita; Grancarić, Ana Marija; Leskovac, Mirela, Cellulose. 21 (2014) 3; pp , ISSN [6] Stana-Kleinschek, Karin; Ribitsch, Volker; Kreže, Tatjana; Fras, Lidija, Materials Research Innovations 6 (2002) 1, pp , ISSN [7] Rupin, Michel; Textile chemist and colorist. 8 (1976) 8, pp , ISSN X. [8] Lewis, David Malcolm; Lei X.P., Textile chemist and colorist. 21 (1989) 10, pp , ISSN X. [9] Hashem, Mohamed; Hauser, Peter; Smith, Brent, Textile Res. J, 73 (2003) 11, pp , ISSN [10] Liu, Zhao-Tie; Yang, Yani; Zhang, Lili; Liu, Zhong-Wen; Xiong, Heping, Cellulose 14 (2007) 4, pp , ISSN [11] Mahltig Boris, Textor Torsten (2008), Nanosols and textiles, 1 st ed. World Scientific, London.

INTERFACE PHENOMENA OF CATIONIZED COTTON WITH EPTAC

INTERFACE PHENOMENA OF CATIONIZED COTTON WITH EPTAC OF CATIONIZED COTTON WITH EPTAC Ana Marija GRANCARIĆ Anita TARBUK Marijn M.C.G. WARMOESKERKEN INTRODUCTION The most important phase in cotton pretreatment and finishing is adsorption of chemical substances