Application of principal component analysis to the FTIR spectra of disk lubricant to study lube-carbon interactions

Lubricant molecules on carbon surfaces are typically present in two distinctive chemical-physical environments, conventionally referred to as bonded and free lubricant. We observe and analyze the spectral shift in the lubricant FTIR spectrum using principal component analysis (PCA) to quantify and understand the bonded and free lubricant states for the lubricant systems Zdol, AM, and ZTetraol. In addition, we performed extended PCA to elucidate lubricant interactions with phosphazene additives. PCA of FTIR spectra is found to be a viable method in quantifying bonded lube ratio as well as in studying the mechanism of lubricant and phosphazene additive-carbon interactions.