nanodiamonds resin and, according to a previous

nanodiamonds were reduced 4 times approaching
0.1. While high loadings of nanodiamonds result in remarkably high hardness and
Young’s moduli of the epoxy– nanodiamonds composites, lower concentrations of nanodiamonds
can be used to improve the mechanical properties177. The bulk Young’s modulus measured in tensile
tests was 25% higher upon addition of 0.5 wt.% as-received nanodiamonds, which
also increased the decomposition temperature. However, due to poor nanodiamonds
dispersion, the storage modulus of the epoxy composite was significantly
reduced, emphasizing the importance of a good dispersion to optimize the
mechanical properties of nanodiamonds –polymer composites. A study on the mode
I and II fracture toughness of nanodiamonds –epoxy composites has shown that,
beyond an improved Young’s modulus and hardness, the mode II fracture toughness
of epoxy– nanodiamonds composites with 0.1 wt.% nanodiamonds is increased. This
is because nanodiamonds is thought to inhibit shear deformation, improving
fracture toughness195. For covalent binding to epoxy, pointed to form
the most strong ND– polymer interface, nanodiamonds terminated with reactive
amino groups was formed by combining ethylenediamine to nanodiamonds –COOH
surface via amide bond (yielding nanodiamonds –CONH(CH2)2NH2, here after named nanodiamonds
–NH2). The rational behind using amino terminated ND is  similar to molecular curing agents, reaction
of nanodiamonds –NH2 with epoxy resin is predicted to result in a covalently
bonded network of nanodiamonds and epoxy molecules. However, to get full
advantage of covalent nanodiamonds –polymer interface, it is unfavourably
essential to have covalent bonds all the way from nanodiamonds surface to the
macromolecules of the matrix. Therefore, first
covalent bonding between the diamine molecules and nanodiamonds particles was
confirmed by FTIR, TG and DSC. When nanodiamonds –NH2 reacted with the epoxy
resin, a strong covalent nanodiamonds –epoxy interface was formed as proof by
DSC, which was used to monitor the reaction. As a result, Young’s modulus of a
composite containing 3.5 vol.% nanodiamonds –NH2 was enhance by 60%196. Also, it was found that in order to
manufacture ND–NH2–epoxy composites with uniformly dispersed nanodiamonds it is
important to keep nanodiamonds –NH2 dispersed in a compatible and inert solvent
without drying.  Tetrahydrofuran (THF)
was chosen for this purpose as it provides a good dispersing medium for nanodiamonds
–NH2, dissolves epoxy resin and, according to a previous report, it does not
react with components of the