| Abstract: | Nylon 11 coatings filled with nanosized silica and carbon black have been produced using the high velocity oxy‐fuel (HVOF) combustion spray process. The physical properties and microstructure of coatings produced from nylon 11 powders with starting particle sizes of 30 and 60 μm have been evaluated as a function of the filler content, filler chemistry, and processing conditions. The nominal filler content was varied from 5 to 20 vol %. Co‐milling of the nano‐sized fillers with the polymer powders produced an embedded 4–8 μm thick filler layer on the surfaces of the polymer particles. Optimization of the HVOF processing parameters based on an assessment of the degree of splatting of polymer particles was accomplished by varying the jet temperature (via hydrogen/oxygen ratio). Gas mixtures with low hydrogen contents minimized polymer particle degradation. The filler was found to be agglomerated at the splat boundaries in the final coating microstructures. Aggregates of silanated silica and carbon black were of the order of 50 nm in size, whereas the aggregates of untreated silica and hydrophilic silica were of the order of 100 nm. The morphology of the polymer and the microstructure of the coatings depended on the filler surface chemistry and the volume fraction of the filler, as well as the initial nylon 11 particle size. Although all filled coatings had higher crystallinities than pure nylon 11 coatings, coatings produced from a smaller starting polymer particle size exhibited improved spatial distribution of the silica in the matrix and lower crystallinity. In addition, coatings prepared from smaller polymer particles had a higher density and lower porosity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1684–1699, 2000 |
