Proceedings of the XV Balkan Mineral Processing Congress, Sozopol, Bulgaria, June 12 – 16, 2013 1157 THE USAGE OF SODIUM BENTONITE IN STYRENE BUTYL ACRYLATE COMPOSITES Onur GÜVEN, Behzad Vaziri HASSAS, Fırat KARAKAŞ 1 Istanbul Technical University, Department of Mineral Processing Engineering, 34469 Maslak, Istanbul ABSTRACT. In recent years, research on polymer composites with mineral fillers have received great interest in terms of improved characteristics on mechanical, rheological and thermal properties. In particular, the usage of layered silicates in composites stems from its distribution characteristics varied upon interlaminar distance within its structure. In this study, the effect of sodium bentonite on mechanical and rheological properties of the composites based on styrene butyl acrylate copolymer which is generally used as binder in different industrial applications depending on its viscosity value. Mechanical properties of the composite such as tensile stress, elongation and elasticity were improved upon addition of sodium bentonite. At the end of the study, optimum amount of sodium bentonite was found considering both mechanical properties and viscosity of the matrix. Keywords: St-BA, Bentonite, Interlaminar. INTRODUCTION Developing composite materials based on polymers and inorganic filler particles has been an attractive approach to achieving better mechanical and thermal characteristics of polymers. Styrene-co-butyl acrylate copolymer (St-BA), owing to its unique properties of being non-toxic, non-pollutant and water borne has been widely used in latex paints, coating, carpet back filler and adhesives. In literature data, mainly organo or purified bentonite after some chemical or physical processes were used as filler material [1-3]. As it is well documented in the literature, introducing a small amount of inorganic filler to the polymer matrix can improve many indices of physicomechanical properties of polymers (Maksimov et al. 2006). The greatest reinforcing effect, as a rule, is accepted to have significant tensile strength (two or more times) values. The purpose of our study is to investigate the effect of sodium bentonite on mechanical properties of St-BA copolymer. In addition, the morphology of composite films were investigated by XRD ( X- Ray Diffractometry) analysis. EXPERIMENTAL STUDIES Materials In experimental studies styrene butyl acrylate copolymer (St-BA) with the trademark ORGANO PST 5010 was used. In particular it constitutes a water-borne emulsion and showing a copolymer structure. The solid content of this emulsion was declared as 50 wt. % depending on the standards ISO 1625 and DIN 53189. In industrial applications, usage of this polymer changes upon its glass transition temperature value which was determined by the data of differential scanning calorimeter in this study as 5 °C. The structure of polymer is shown in Figure 1 Fig. 1 Structure of styrene-butyl acrylate copolymer As filler, sodium bentonite with pure lump size was supplied by Resadiye concentrator. The sample was controlled grinded by a ring mill to obtain bentonite powder with a mean particle size of 63 µm. For providing compatible surface properties, wetting agent as the aqueous solution of ammonium poly acrylate of trademark Ardewatt A was used. In order to prevent foams, ultra fine dispersion of wax in mineral oil with the trademark Elementis Dapro DF7010 was used as anti-foaming agent. Characterization and measurements Mechanical tests were correlated with the samples conforming to the sample standard namely ASTM D638-08 for the specimen sizes of 90x20x2 mm. Mechanical properties such as tensile strength, elongation and elasticity parameters were determined under uni axial tension on a Davotrans FU testing unit at room temperature. Specimens were loaded at a constant tension rate of 50 mm min-1. Determination of elongation parameters were carried out by comparing the initial length to final length of the composite films. All tests were carried out according to the ASTM D 5026. Basic mechanism occurring during tests was shown in Figure 2. Fig. 2 Basic mechanisms occurring during tensile strength tests In Figure 3, the production flowchart for composite material was shown. Composite Films Mechanical mixing at 800 rpm for 5 minutes Mechanical mixing at 1000 rpm for 20 minutes Styren-Co-Butyl Acrylate Copolymer Wetting agent addition Anti-Foamer addition Inorganic Filler Addition Pouring onto teflon molds Drying at 30 °C Fig. 3 The production flowchart for composite films with sodium bentonite Characterization and measurements Micron sized bentonite particles and their dispersions in the composites at different ratios are shown in Fig. 4. Micron sized particles in polymer matrix are well identified by XRD even at low