Thermodynamic prediction of filler surface modification by APTES on corrosion resistance of nano-TiO2/waterborne epoxy coatings

Abstract

Common techniques for creating novel coatings include chemically modifying inorganic fillers and exploring how modifications affect coating service performance. However, it frequently takes a lot of time and tedious attempts to get the ideal alteration degree for fillers. Although the surface energy of the fillers is thought to be a significant thermodynamic parameter, it is still unknown how chemical modification affects surface energy and how the properties of fillers in a coating relate to the quantization difference of thermodynamic parameters. In this study, the impact of chemical modification on the quantization difference of nano-TiO2 surface energy has been uncovered. Creating a “wetting-reagglomeration-adsorption” isogram by utilizing three surface interfacial parameters has also been achieved: the contact angle between the liquid resin and the filler, the driving energy of the filler reagglomeration, and the polymer molecules' diffusion energy at the filler/coating interface. The relationship between the quantitative difference of thermodynamic parameters and the dispersion, compatibility and interfacial strength of the fillers in the waterborne epoxy was predicted by the isocontour map. From the isocontour map, the modified nano-TiO2 fillers with 4.04 APTES molecules/nm2 shows the minimum ∆Wa of 16.17 mJ/m2 and the maximum Ws of 23.15 mJ/m2 in the composite coating, which is predicted to exhibit the best dispersibility and the strongest interfacial strength. The prediction results were successfully verified by the techniques of microscopic morphology observation (TEM and SEM), mechanical properties tests (DMA and tensile tests), and corrosion resistance tests (EIS and salt spray tests). This work has a significant guiding role in the development of the filler modifications for the creation of novel coatings.