Numerical predictions and experimental observations havebeen correlated to improve the qualitative understanding of thedegree of thermal degradation occurring during the HVOFspray deposition of Nylon-11. Particle residence time (<1 ms)in the HVOF jet was insufficient for significant decompositionof the Nylon-11 but was sufficient for noticeable discoloration(yellowing) of the particles of a powder with a mean particlesize of 30 μm. Experimental observations showed this to bethe case even though numerical predictions indicated that thetemperature of a 30 μm diameter particle should beconsiderably higher than the upper degradation limit of Nylon-11. Initial thermal oxidation of Nylon-11 promotes theformation of carbon-carbon double bonds that strongly absorbin the visible spectrum even at concentrations of parts permillion, resulting in discoloration of the Nylon.
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