Maximizing Youngʹs modulus of aminated nanodiamond-epoxy composites measured in compression

Nanodiamond, due to its superior hardness and Youngʹs modulus in combination with its large surface area holds great potential for the mechanical reinforcement of polymer matrices. However, it is still not possible to take full advantage of these properties in polymer matrix composites. The main reasons are poor dispersion, agglomeration and a weak interface between nanodiamond and the polymer. Aminated nanodiamond can be used to form a strong covalent interface with an epoxy polymer. We show how Youngʹs modulus can be further improved if an interference of nanodiamonds amino groups with the epoxy stoichiometry is taken into account. Dispersion of nanodiamond is improved by slightly adjusting the manufacturing process, thus increasing Youngʹs modulus of the composites. Predictions by a micromechanics homogenization method that consider nanodiamond agglomeration and dispersion suggest that Youngʹs modulus can be further increased by slightly improving both parameters. For the first time we show that epoxy can be cured solely by nanodiamonds amino groups without any additions of curing agent, resulting in a compositeʹs Youngʹs modulus measured by nanoindentation of up to ∼18 GPa – a 700% improvement over neat epoxy.