Prediction of Acid-Base (Polar) Component Free Surface Energy in Dispersion-Filled Polymer Composites

The paper develops a predictive model to determine the influence of the magnitude of the acid-base (polar) component of the free surface energy (FSE) of polymers and fillers, as well as the volume fraction of fillers on the acid-base (polar) component of the FSE of a polymer composite. Mathematical equations and graphical relationships illustrating these relationships are presented. The model is based on the assumption that in composites the magnitude of the FSE is partially determined by acid-base (polar) interactions between functional groups at the “polymer−filler” interface. Using the predictive model, it was established that knowing the acid-base characteristics of the polymer and filler, it is possible to predict what kind of surface character a particular filled composite will have − acidic, alkaline, or predominantly neutral. Based on the results obtained, it can be argued that the acid-base (polar) component of the free surface energy (FSE) can be a reflection of the properties of polymer composites, namely, resistance to the action of aggressive media, such as water, aqueous solutions of acids and alkalis, polar organic and inorganic solvents, etc. To verify the proposed model, the energy characteristics of the surfaces of epoxy composites based on epoxy oligomer with diethylenetriamine and mineral fillers of different chemical nature – rutile and bentonite – were experimentally investigated. Using experimental studies and calculations using the model, it has been shown that the FSE values ​​of the composite are mostly (70-75%) determined by processes at the “polymer−filler” phase interface, and the rest is due to chemical, physicochemical, intermolecular and other interactions between the functional groups of the polymer and hardener.