Section: "Nanocomposites and nanomaterials"

Epoxy molecular structure alteration in graphene –epoxy nanocomposites: loading effects
Gorelov B.M.1, Gorb A.M.2, Czapla Z.3, Wacke S.3, Nadtochiy A.B.2, Kuryliuk V.V.2, Kostrzewa M.3, Ingram A.3, Polovina O.I.2, Sigareva N.V.1
1 Chuiko Institute of Surface Chemistry of the National Academy of Sciences of Ukraine. General Naumov Street, 17, Kyiv-03164, Ukraine. 
E-mail: microft2@ukr.net
2 Taras Shevchenko National University of Kyiv. Hlushkova Avenue, 4, Kyiv-03127, Ukraine.
3 Department of Physics, Opole University of Technology. Ozimska, 75, 45-370 Opole, Poland.

This report shows a capability to control molecular structure alteration in epoxy by using the multilayered graphene nanoplatelets (MLGNP) prepared by using the ultrasonically-assisted electro-chemical technique. ED-20 epoxy curried with polyethylene-polyamine (PEPA) hardener was the polymer matrix and the filler’s loading (Cf) of the nanocomposites varied from 0.1% to 5.0% by weight.
Next, physical properties of the nanocomposites have been experimentally studied with using various techniques. The data obtained by using the thermal-desorption mass-spectroscopy shows that MLGNP stabilize resin’s molecular structure due to fastening unlinked dipole moieties of the chains to the nanoplatelets via carbon dangling bonds located on its both lateral surfaces and the structural defects, and the effect results in improving heat-resistance of the epoxy.
The ultrasound-probing data shows that the Young’s dynamic module (E) grows slightly at low loadings of Cf ≤ 0.5% and then decreases smoothly with increasing Cf. Such run of E(Cf) correlates with the results obtained by a static mechanical-loading technique. Calculations of E(Cf) carried out by using molecular dynamic simulation revealed that E increases at low loadings (Cf ≤ 0.5%) and decreases when Cf increases further.
Dielectric measurements have been made in the ranges of [4Hz-8MHz] and [95-350 K] and show that ε1 and ε2 increases with increasing Cf. An increment in ε2 may be related with increasing electron-gas-related losses of graphene particles versus increasing Cf. A negligible variations in ε1 at 1% < Cf < 2% is a result of resin’s structure stabilization. The free volume portion fV has been calculated by using Tao-Eldrup model, via parameters obtained from the PALS-measurements. The dependence fV(Cf) proved to be descending, that evidences tightening 3D-molecular network of the nanocomposites. Also, PALS-data indicate that electron density of the nanocomposites varies with increasing the loading.