Nanodiamond, due to its superior hardness and Young's 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 Young's 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 Young's modulus of the composites. Predictions by a micromechanics homogenization method that consider nanodiamond agglomeration and dispersion suggest that Young's 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 composite's Young's modulus measured by nanoindentation of up to similar to 18 GPa - a 700% improvement over neat epoxy. (C) 2012 Elsevier Ltd. All rights reserved.