Impact of moisture and plasticizer properties on polymer–plasticizer physical mixing performance

The ability for polymers and additives to physically mix in many industrial applications is dictated by a combination of kinetic and thermodynamic factors. The presence of moisture may complicate the mixing performance as water can interact at various degrees with each of the components; this depends on the hydrophilicity of the materials. In this study, the physical mixing behavior of a ternary system consisting of a hygroscopic polymer (copovidone), a plasticizer, and water was examined. Three different liquid plasticizers with a range of hydrophilic–lipophilic properties and viscosities were evaluated for their physical mixing performance and the impact of their water content. Inverse gas chromatography was introduced as a new method for measuring the surface characteristics of the physical mixtures to quantify the mixing performance. Through the application of the Flory–Huggins model to understand the thermodynamic behavior of the system, it was shown that mixing was less effective in a system of high water content for a hydrophobic plasticizer. However, the underlying thermodynamic unfavorability of such a system could be overcome by kinetic influence to provide a good mixing performance. Specifically, as the viscosity of the plasticizer decreased, the influence of the thermodynamic characteristics was found to become less apparent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41679.