Epoxy Molecular Structure Alteration in Graphene …
461
2 Experimental Technique
2.1 Materials and Samples
Multilayered graphene nanoplatelets (MLGNPs) for our experiments have been
prepared from graphite flakes by using the electrochemical technique described by
Xia et al. [41]. The details of our preparation technique and structural properties of
the platelets synthesized are described in [24].
The commercially available ED-20 (Ukraine) DGEBA-epoxy with molecular
weight (M n ) 400 g/mol and the epoxy groups content (epoxy number) ~20.4% [42,
43] was used as the host polymer for preparing nanocomposites. The structural
formulae of a repeating molecular unit of DGEBA-oligomer and molecules of hardening polyamines playing as amine cross-links (ACLs) for the oligomer’s units are
shown in Fig. 1.
The Polyethylene-polyamine (PEPA) was used as a curing agent. PEPA is a mix
of primary amines of various molecular masses; its general structural formula is
H 2 N[−CH 2 CH 2 NH−] n H, where n = 3 corresponds to triethylenetetramine (TETA),
n = 4—to tetraethylenepentamine (TEPA), and n = 5 to pentaethylenesextamine
(PESA). The PEPA is widely used as a hardener of epoxy resins due to its explosionproof and hard ignitable properties [43]. Polyfunctional primary amines form an
important class of epoxy hardeners. Primary amines undergo an addition reaction
with the epoxide group to form a hydroxyl group and a secondary amine. The
secondary amine can further react with an epoxide to form a tertiary amine and
an additional hydroxyl group [27].
Given that the most important polar groups (N, OH) are located close to the
cross-linking nodes, the increase of the CLD leads to an increase of the polar moiety
density [44]. Under curing, the oligomer units combine with each other into long
epoxy macromolecular chains (EMCs). The EMCs, in turn, undergo numerous entanglements and cross-links by amine molecules, thus forming 3D-network molecular
Fig. 1 The structural formulae of DGEBA-epoxy and hardening polyamines (TETA, TEPA, PESA)
461
2 Experimental Technique
2.1 Materials and Samples
Multilayered graphene nanoplatelets (MLGNPs) for our experiments have been
prepared from graphite flakes by using the electrochemical technique described by
Xia et al. [41]. The details of our preparation technique and structural properties of
the platelets synthesized are described in [24].
The commercially available ED-20 (Ukraine) DGEBA-epoxy with molecular
weight (M n ) 400 g/mol and the epoxy groups content (epoxy number) ~20.4% [42,
43] was used as the host polymer for preparing nanocomposites. The structural
formulae of a repeating molecular unit of DGEBA-oligomer and molecules of hardening polyamines playing as amine cross-links (ACLs) for the oligomer’s units are
shown in Fig. 1.
The Polyethylene-polyamine (PEPA) was used as a curing agent. PEPA is a mix
of primary amines of various molecular masses; its general structural formula is
H 2 N[−CH 2 CH 2 NH−] n H, where n = 3 corresponds to triethylenetetramine (TETA),
n = 4—to tetraethylenepentamine (TEPA), and n = 5 to pentaethylenesextamine
(PESA). The PEPA is widely used as a hardener of epoxy resins due to its explosionproof and hard ignitable properties [43]. Polyfunctional primary amines form an
important class of epoxy hardeners. Primary amines undergo an addition reaction
with the epoxide group to form a hydroxyl group and a secondary amine. The
secondary amine can further react with an epoxide to form a tertiary amine and
an additional hydroxyl group [27].
Given that the most important polar groups (N, OH) are located close to the
cross-linking nodes, the increase of the CLD leads to an increase of the polar moiety
density [44]. Under curing, the oligomer units combine with each other into long
epoxy macromolecular chains (EMCs). The EMCs, in turn, undergo numerous entanglements and cross-links by amine molecules, thus forming 3D-network molecular
Fig. 1 The structural formulae of DGEBA-epoxy and hardening polyamines (TETA, TEPA, PESA)