Synthesis and micromechanical properties of polymer nanocomposites based on graphene oxide
H.V. Rusakova1, L.S. Fomenko1, S.V. Lubenets1, A.V. Dolbin1, N.A. Vinnikov1, R.M. Basnukaeva1, M.V. Khlistyuck1, and A.V. Blyznyuk2
1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
2National Technical University “Kharkiv Polytechnic Institute”, 2 Kyrpychov Str., Kharkiv 61002, Ukraine
Received October 9, 2019, published online January 27, 2020
The influence of the small (≤ 1 wt%) additions of thermally reduced graphene oxide on microhardness and kinetics of microindentation in polymers of two types (polystyrene which is thermoplastic with glass transition temperature Tg ≈ 373 K and polyester resin which is thermosetting plastic with Tg ≈ 300 K) was studied. In a microindentation test, room temperature creep of the nanocomposites was described in the framework of the rheological three–element Kelvin–Voigt model; the parameters of the model and the influence of graphene oxide on them were defined. In the polystyrene–0.3 wt% graphene oxide nano-composite unrelaxed and relaxed elastic moduli and the modulus characterizing high-elasticity deformation increased by 11, 40, and 87% respectively as compared with initial polystyrene; in this case, microhardness increased by 38 and 45% for different sam-ple sets. The obtained results show that the presence of graphene oxide in the nanocomposite severely restricts the mobility of mo-lecular segments. Addition of 0.3 wt% graphene oxide in polyes-ter resin was accompanied by increasing of the mechanical glass transition temperature of the resin by no less than 5 K. This resulted in the change of relaxation state of the polymer: whereas polyester resin at room temperature behaves like an elastomer, the polyester resin–0.3 wt. % graphene oxide nanocomposite shows the glassy properties. At room temperature microhardness of the polyester resin–glass fiber fabric–graphene oxide nano-composites with 0.5 and 1 wt. % graphene oxide increased by 20 and 80% as compared with microhardness of polyester resin–glass fiber fabric composite. In the range of 77–298 K the temperature dependencies of microhardness of the nanocomposites with the polyester matrix were obtained; the temperature regions in which microdeformation of the composites has reversible character were revealed, it is connected with the forming of crazes with a re-duced glass transition temperature.
Key words: nanocomposites, polystyrene, polyester resin, graphene oxide, microindentation, low temperatures.