Estimation of polyurethane-carbon black interactions by means of inverse gas chromatography

The properties of composites depend mainly on the interfacial interactions between filler and matrix that can be related to the adhesion between filler and polymer matrix. In this study the work of cohesion between the carbon black particles - Wcoh - and the thermodynamic work of adhesion - Wa - between four carbon blacks of different specific surface area and surface chemistry (nature and content of carbon-oxygen functional groups) and thermoplastic polyurethane were calculated by means of inverse gas chromatography (IGC) at infinite dilution. IGC derived data indicated that the work of adhesion increased by increasing the surface area of the carbon black, but the opposite trend was found in Wa/Wcoh and work of cohesion. According to the Wa/Wcoh values the filler particles should be well dispersed into the polyurethane matrix giving homogenous composites. The carbon black-thermoplastic polyurethane interactions determined by plate-plate rheology showed the same trend than that for the Wa/Wcoh values. However, the thermodynamic work of adhesion values derived from IGC were not in agreement with the carbon black-polyurethane interfacial interactions, likely due to the dominant effect of the carbon black in reducing the crystallinity and increasing the degree of phase separation of the thermoplastic polyurethane.