Functionalizing organic powder coatings with nanoparticles through ball milling for wear applications

Abstract

Epoxy powder coatings were functionalized with nanosilica to improve wear resistance. Ten different organic coatings were studied: 0.25–1% (by wt.) of SiO2 nanoparticles (both hydrophilic -HL- and hydrophilic -HB-) were added to epoxy powders. The homogeneity of the distribution of the silica nanoparticles in the epoxy powder matrix was achieved with an innovative ball-milling mixing method. This homogeneity was confirmed through transmission electron microscopy (TEM) observations. Powder coatings were sprayed and cured on steel sheets. The wear resistance of the coatings was evaluated in reciprocating wear equipment, measuring the depth and the width of the wear tracks obtained by an optoelectronic microscopy. Results reveal very significant improvement in wear resistance, with the best wear performance being observed for the epoxy reinforced with 0.75%HB SiO2 nanoparticles. This is related to the enhanced crosslinking of the matrix in the coatings due to SiO2, as shown by the mechanical properties. The curing kinetics of the functionalized epoxy powders was studied by non-isothermal differential scanning calorimetry (DSC). Activation energies (Ea) calculated from DSC are related to in the diffusion-controlled reactions.