1490 ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version) Fibers and Polymers 2018, Vol.19, No.7, 1490-1499 Mechanical and Dynamic Mechanical Studies on Epoxy-Cobaltous Sulfate Polymer Hybrids Shruti S. Devangamath 1 , Blaise Lobo 1 * , Saraswati P. Masti 2 , and Shivayogi Narasagoudr 2 1 Department of Physics, Karnatak University’s Karnatak Science College, Dharwad, Karnataka 580001, India 2 Department of Chemistry, Karnatak University’s Karnatak Science College, Dharwad, Karnataka 580001, India (Received January 18, 2018; Revised March 25, 2018; Accepted May 18, 2018) Abstract: Cobaltous sulfate heptahydrate (CoSO ·7H O) was incorporated as filler into diglycidyl ether of bisphenol A (DGEBA) based epoxy resin system, to prepare organic-inorganic polymer hybrid materials. Mechanical tensile studies and dynamic mechanical analysis (DMA) were carried out in order to study the static and dynamic mechanical properties of the prepared hybrid films. Mechanical tensile studies were carried out at room temperature, at a test speed of 30 mm/min. Highest tensile strength of 24.74±2.42 MPa was achieved for 4.44 wt% filler level (FL), along with an increase in the value of Young’s modulus. Storage modulus (E'), loss modulus (E''), damping factor (tan δ) were obtained by DMA studies. Glass transition temperature (T ) was obtained for pure epoxy and filled epoxy, for various FLs varying from 0.28 wt% to 5.00 wt%. Pure epoxy showed highest T value compared to filled epoxy hybrids. Highest storage modulus of 9.5 GPa was obtained for 2.22 wt% FL, which also showed highest loss modulus peak. Parameters like effectiveness coefficient (C) and crosslink density were calculated from the storage modulus data. Loss modulus and tan δ curves were analyzed to study the energy dissipation properties of prepared hybrid films. Activation energy (E ) value for glass transition was obtained from damping factor (tan δ), which showed highest E value of 630.5 kJmol , for 4.44 wt% FL. DMA studies for various FLs were carried out at different test frequencies in order to study the changes in dynamic mechanical properties of the prepared hybrid materials with respect to frequency. Keywords: Epoxy resin, Cobaltous sulfate heptahydrate, Polymer hybrid materials, Mechanical tensile studies, Dynamic mechanical analysis Introduction Epoxy polymers are extensively used as polymer matrices in composites, nanocomposites and polymer hybrid materials. Highly cross linked and amorphous microstructure of cured epoxies results in many important properties like high modulus, high failure strength, low creep and good performance at high temperatures, high chemical and solvent resistance as well as high distortion temperatures [1, 2]. Particulate fillers influence the physical and mechanical properties of polymers in many ways leading to useful applications [3]. Particle shape and packing, filler con- centration and relative modulus of the components affect the mechanical properties of the filled polymeric materials [4]. Young’s modulus or the stiffness of the polymers can be increased by incorporation of nano or micro inorganic particles, as they have greater stiffness compared to polymer matrix [5]. Particle - matrix interfacial adhesion plays an important role in increasing the stress - transfer and hence, it improves strength of the material. Nanoparticle addition to the polymer matrix is highly vulnerable to particle agglomeration, which decreases the interfacial interaction and also leads to concentration of thermal stress at the agglomeration sites [6]. A perfect adhesion means that, there is no relative movement of the filler and matrix phase across the interface up to a load being considered. At higher stresses, the interfacial bond may break and adhesion is not perfect [7]. Though cross linked polymers have many advantages, crack growth is a serious drawback for thermo- setting polymers. This can be overcome by incorporation of inorganic particles; in order to increase toughness of the cross linked resins [8]. Another outstanding feature of epoxy systems is the possibility to tune the network structure by varying the crosslink density, either by varying the extent of cure or by varying the ratio of resin to the hardener [9]. Crosslink density highly influences the relaxation properties of epoxy systems, which in turn affects the glass transition temperature (T g ). Filler materials which can improve the properties of the host polymer, without complicated surface treatments, have gained greater attention in composite and hybrid material fabrication [10]. Dynamic mechanical properties of polymers are of considerable interest, particularly if they are determined over wide range of temperature and frequency [11]. Stiffness and damping properties of materials can be studied by DMA analysis in terms of storage modulus, loss modulus and loss tangent or damping factor, which are obtained by applying sinusoidal stress to the material under study. The viscoelastic nature of polymer systems is well established experimentally by carrying out DMA analysis. So when a polymer material is vibrated, part of the applied energy is stored and a part of it is dissipated. Damping properties of polymers are studied by loss modulus and loss tangent parameters. Damping is ability of a material to absorb heat, which is low for stiff materials like metals; the high damping of polymers is considered many times as a boon [12]. *Corresponding author: blaise.lobo@gmail.com DOI 10.1007/s12221-018-8031-4