Abstract
The high velocity oxy-fuel (HVOF) combustion spray technique has previously been shown to be an excellent solution for depositing crystalline matrix nano-reinforced polymer coatings. The use of multiple scales of reinforcement is expected to improve the load transfer from the larger reinforcing particles to the matrix through the mediation of the smaller particles. The initial step in developing multi-scale coatings is studying the effects of reinforcement size on distribution and properties. Nylon 11 coatings filled with silica particulates of 7 nm, 20 nm, 10µm and 100µm have been produced using the high velocity oxy-fuel (HVOF) combustion spray process. The physical properties and microstructure have been evaluated as a function of the reinforcement size. Nylon 11 was co-milled with the fillers to a 10% volume fraction. The filler was agglomerated at the splat boundaries in the final coating microstructures. All filled coatings had significant changes in x-ray pattern relative to pure nylon 11 coatings, indicative of both increased crystallinity and changes in crystal structure. Coatings containing the smallest reinforcements exhibited improvements of 40 % in scratch and 84 % in wear resistance above those containing the largest reinforcement particles in coatings with nominal 10 vol. % of hydrophobic silica. This increase appeared to be primarily due to filler addition and increased matrix crystallinity.
