The high velocity oxy-fuel (HVOF) combustion spray process has been demonstrated as a viable approach for producing nano-reinforced semi-crystalline polymer composite coatings by controlling both the particle dwell time and substrate temperature. HVOF sprayed polymer matrix composites incorporating ceramic reinforcements ranging from 7 nm to 100 urn are being studied to bridge between the nano and conventional size scale regimes. Microstructural characterization is being used to analyze the dispersion and distribution of the ceramic reinforcements. The effect of particle size on dispersion and distribution, and the influence of substrate temperature on coating adhesion, have been investigated. Changes in crystallinity, as determined by Thermal Gravimetric Analysis (TGA), are being correlated to nano/multi scale coating microstructures, reinforcement loadings and processing parameter variations. Results of optical and scanning electron microscopy, scratch testing and TGA characterization of the feedstock materials and sprayed coatings will be presented. Coatings of nominal 60 um Nylon-11 with 10 vol. % of nano and micron sized hydrophilic silica reinforcements exhibited ~22 % improvement in scratch resistance compared to pure Nylon-11 coatings. A 15 % improvement in scratch resistance was obtained for coatings containing 10 vol. % of nano scale hydrophilic silica reinforcement.
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