Elastomers based on NR/BR/SBR ternary rubber blend: Morphological, mechanical and thermal properties

Available on line at Association of the Chemical Engineers of Serbia AChE www.ache.org.rs/CICEQ Chemical Industry & Chemical Engineering Quarterly Chem. Ind. Chem. Eng. Q. 25 (1) 31−38 (2019) SLAVIŠA JOVANOVIĆ1 VOJISLAV JOVANOVIĆ2 GORDANA MARKOVIĆ3 SUZANA SAMARŽIJA-JOVANOVIĆ2 ZORAN MILIĆEVIĆ4 MILENA MARINOVIĆ-CINCOVIĆ5 JAROSLAVA BUDINSKI-SIMENDIĆ6 1 Mitas d.o.o, Ruma, Serbia Faculty of Natural Science and Mathematics, University of Priština, Kosovska Mitrovica, Serbia 3 Tigar AD, Pirot, Serbia 4 Faculty of Economics, University of Priština, Kosovska Mitrovica, Serbia 5 Institute of Nuclear Science Vinča, University of Belgrade, Belgrade, Serbia 6 Faculty of Technology, University of Novi Sad, Novi Sad, Serbia 2 SCIENTIFIC PAPER UDC 678.074:678.046.2:66.017:54 CI&CEQ ELASTOMERS BASED ON NR/BR/SBR TERNARY RUBBER BLEND: MORPHOLOGICAL, MECHANICAL AND THERMAL PROPERTIES Article Highlights • • • • The influence of amount SBR rubber in NR/BR/SBR rubber blends was investigated The amount of the CB in NR/BR/SBR rubber blend is 60 phr The NR/BR mass ratio in ternary nano-blends is 1:1 The optimum content of SBR rubber in NR/BR/SBR rubber blend is 40 phr Abstract The elastomeric materials based on NR/BR/SBR ternary rubber blend were investigated. The polyisoprene (NR), butadiene (BR) and styrene butadiene (SBR) rubbers were used as network precursors and carbon black (CB) as an active filler (60 phr) for elastomeric materials preparation. For sample preparation, the mass ratio of NR to BR was constant, 1:1, but the SBR content was varied from 0 to 80 phr. The morphological, mechanical and thermal properties of prepared elastomeric materials were determined using scanning electron microscopy (SEM), mechanical tensile measurements and thermogravimetric analysis (TGA). Mechanical properties were assessed before and after thermooxidative aging during 168 h at 100 °C. The values of tensile strength, elongation at break, and hardness decrease up to 40 phr of SBR content and after that are increasing, but abrasion resistance of ternary rubber blends increases. Тhe thermal decomposition temperature obviously shifted to a higher temperature for the sample with 40 phr of SBR. Keywords: carbon black, mechanical properties, ternary rubber blends, thermo-oxidative aging, thermal properties. One of the most effective methods for developing new polymer materials is polymer blending. This way of creating new materials has been used for over two decades and has been of great importance for science and industry [1]. From the industrial point of view, mixtures of elastomers have multiple applications, reducing the cost of making products improve the flow [2]. The most commonly used tire rubbers are natural rubber (NR), styrene-butadiene rubber (SBR) and polybutadiene rubber (BR). Great use of natural Correspondence: S. Samaržija-Jovanović, Faculty of Natural Science and Mathematics, University of Priština, Lole Ribara 29, 38220 Kosovska Mitrovica, Serbia. E-mail: , Paper received: 6 November, 2017 Paper revised: 3 June, 2018 Paper accepted: 19 June, 2018 https://doi.org/10.2298/CICEQ171106016J rubber (cis-1,4-polyisoprene) in the elastomeric materials for tires is due to its effect on dynamic properties as a result of high stereoregular microstructure and the free rotations around the methylene C-C bond [3]. An important factor in the rubber blending is the solubility parameter. A big difference in the solubility parameters gives an inhomogeneous blend. NR and SBR have similar solubility parameters (both close to 10.0). According to [4], fatigue and cracking of elastomeric materials based on NR rubber can be improved by adding small amounts of SBR rubber. Many studies showed that the mechanical properties of such a blend can be significantly enhanced by adding an appropriate compatibilizer [5]. Mixing of SBR with NR may improve the tensile strength [6]. Mohan et al. studied the influence of nano-clay on the tensile strength, hardness, tear and heat stability of NR/SBR blends [7]. Making the interior of wetting the 31 S. JOVANOVIĆ et al.: ELASTOMERS BASED ON NR/BR/SBR… Chem. Ind. Chem. Eng. Q. 25 (1) 31−38 (2019) filler, and its dispersion in the polymer matrix, as well as filler-polymer interaction, increases the mechanical and electrical properties of the CB polymer composites [8]. Carbon black (CB) with unique nanoscale structure combined with the high strength of the carbon-carbon bondings and a large aspect ratio opens up a wide range of new applications. However, the physical properties of the CB-polymer composites are often below expectations, because a sufficiently efficient force transfer between the polymer matrix and CB has not yet been reached. To take advantage of excellent mechanical and electrical properties of CB in polymer composites, internal wetting and dispersion of the filler in the polymer matrix must improve [8]. It is known that the smaller the contact angle between the polymer and filler, the better the wetting of fillers and stronger polymer-filler interaction can be obtained. Although the contact may be calculated from the surface tension of the individual components of the mixture, is not sufficient for description of the complex filler polymer wetting process [9]. Analysis of rubber-filler gel after extraction experiments (bound rubber measurement) by means of nuclear magnetic resonance (NMR), pyrolysis gas chromatography (PGC) and Fourier-transform infrared spectroscopy (FTIR), as well as thermogravimetric analysis (TGA), was carried out for qualitative and quantitative characterization of the physical background of the fillerpolymer interaction in carbon black or silica-filled rubber compounds [10]. If the rubber blend consists two or more rubbers, the bonding filler aggregate with rubber is different because of their affinities [11]. The goal of this applicative work was to prepare carbon black reinforced elastomers based on three network precursors: polyisoprene (NR), polybutadiene (BR) and styrene butadiene (SBR). The effect of SBR rubber content on its mechanical properties and thermal stability was also determined. CBS (1.4 phr); diphenylguanidine, DPG (1 phr); N-(cyclohexylthio)phthalimide, CTP 100 (0.2 phr) and sulfur (2 phr). The content of zinc oxide was 3 phr. The content of stearic acid was 2 phr. The content of the naphthenic oil was 10 phr. Formulations of rubber compounds are shown in Table 1. EXPERIMENTAL Materials Materials used in this manuscript are the same as the ones used in manuscript [12]. For sample preparation, the NR to BR rubber mass ratio was constant, 1:1, while the SBR rubber content was varied from 0 to 80 phr*. Six samples of NR/BR/SBR ternary rubber blends (50/50/0; 40/40/20; 30/30/40; 25/25/50; 20/20/60 and 10/10/80 mass ratio) reinforced with 60 phr of CB were prepared. The curing system conN-cyclohexyl-2-benzothiazolesulfenamide, tained: * Mass part per hundred mass parts of rubber. 32 Table 1. Formulation of (...truncated)