460
B. M. Gorelov et al.
networks with DGEBA-type resins providing good physical properties, including
excellent chemical and solvent resistance. Other advantages include low viscosity,
ambient cure temperature, a little color, and low cost [28]. Although PEPADGEBA-epoxies possess limited flexibility and toughness (and thermal resistivity)
as compared to resins cured with aromatic amines, the latter have now largely
been replaced by aliphatic or cycloaliphatic alternatives taking health concerns with
handling epoxy materials into account [29, 30]. However, epoxy resins are brittle and
have poor resistance to crack propagation [31, 32]. Consequently, certain efforts have
been undertaken toward remedying some shortcomings from amine-cured epoxies.
From the other hand, physical properties of G-PNCs are affected by properties of
graphene itself, namely, type, size (aspect ratio) and shape, also filler morphology
(namely, dispersion/agglomeration, orientation, waviness), loading level, and the
thermal resistance of an interface between graphene and epoxy matrix [16, 20, 33].
Generalizing the results of earlier studies, it can be concluded that they revealed
two opposite effects of graphenic filler on molecular structure of a host epoxy matrix:
(1) restricting macromolecular chain mobility [5, 34] due to strong interfacial
interactions;
(2) lowering the cross-linking degree (CLD) of epoxy [5, 35–37].
Thus, the above-mentioned circumstances—a great variety of epoxy systems
studied and a spread in characteristics of filling graphenic nanoparticles hamper
our understanding of graphene-epoxy interfacial interaction mechanisms that impact
strongly the overall properties of graphene-epoxy nanocomposites.
Also, it is necessary to underline that utilizing the pristine graphene as nanofiller
for polymers is strongly limited by its high-cost production and low yields. In
contrast, multilayered graphene nanoplatelets (MLG), which may contain tens of
graphene layers, have emerged as one of the attractive nanofillers for polymer
composites providing an excellent balance between multifunctional properties and
cost [38–40]. Another advantage of filing epoxy with MLG is a possibility to tailor
physical parameters of a nanocomposite material by either varying morphological characteristics of MLG (such as aspect ratio, orientation, number of layers)
or modifying its surface chemically.
Thus, the problem to treat molecular structure alterations in graphene-based epoxy
nanocomposites and thus to predict their performance remains a big challenge for
polymer material science. Therefore, this study has been undertaken in order to obtain
better awareness of 3D-molecular network alterations in MLG-based DGEBA-epoxy
nanocomposites from comparing loading effects in structure-sensitive properties,
namely dielectric, thermal stability, and structural integrity.
B. M. Gorelov et al.
networks with DGEBA-type resins providing good physical properties, including
excellent chemical and solvent resistance. Other advantages include low viscosity,
ambient cure temperature, a little color, and low cost [28]. Although PEPADGEBA-epoxies possess limited flexibility and toughness (and thermal resistivity)
as compared to resins cured with aromatic amines, the latter have now largely
been replaced by aliphatic or cycloaliphatic alternatives taking health concerns with
handling epoxy materials into account [29, 30]. However, epoxy resins are brittle and
have poor resistance to crack propagation [31, 32]. Consequently, certain efforts have
been undertaken toward remedying some shortcomings from amine-cured epoxies.
From the other hand, physical properties of G-PNCs are affected by properties of
graphene itself, namely, type, size (aspect ratio) and shape, also filler morphology
(namely, dispersion/agglomeration, orientation, waviness), loading level, and the
thermal resistance of an interface between graphene and epoxy matrix [16, 20, 33].
Generalizing the results of earlier studies, it can be concluded that they revealed
two opposite effects of graphenic filler on molecular structure of a host epoxy matrix:
(1) restricting macromolecular chain mobility [5, 34] due to strong interfacial
interactions;
(2) lowering the cross-linking degree (CLD) of epoxy [5, 35–37].
Thus, the above-mentioned circumstances—a great variety of epoxy systems
studied and a spread in characteristics of filling graphenic nanoparticles hamper
our understanding of graphene-epoxy interfacial interaction mechanisms that impact
strongly the overall properties of graphene-epoxy nanocomposites.
Also, it is necessary to underline that utilizing the pristine graphene as nanofiller
for polymers is strongly limited by its high-cost production and low yields. In
contrast, multilayered graphene nanoplatelets (MLG), which may contain tens of
graphene layers, have emerged as one of the attractive nanofillers for polymer
composites providing an excellent balance between multifunctional properties and
cost [38–40]. Another advantage of filing epoxy with MLG is a possibility to tailor
physical parameters of a nanocomposite material by either varying morphological characteristics of MLG (such as aspect ratio, orientation, number of layers)
or modifying its surface chemically.
Thus, the problem to treat molecular structure alterations in graphene-based epoxy
nanocomposites and thus to predict their performance remains a big challenge for
polymer material science. Therefore, this study has been undertaken in order to obtain
better awareness of 3D-molecular network alterations in MLG-based DGEBA-epoxy
nanocomposites from comparing loading effects in structure-sensitive properties,
namely dielectric, thermal stability, and structural integrity.