Understanding and optimizing the activation mechanism of amide wax used as a rheological modifier in solvent-borne paint

Rheological modifiers adjust how paint behaves during and after application, ensuring smooth spreading, pre- venting drips or sagging, and maintaining uniform consistency. Some modifiers must undergo specific activation processes to achieve their full potential. Amide waxes are chemically characterized by their long-chain fatty acid structures and amide functional groups. Upon dissolving, the wax molecules align in fibrillar forms by inter- molecular forces, and the consecutive network of fibrils increases viscosity. This study aims to identify the parameters influencing the activation of amide wax and propose an optimal activation method. The impact of polar solvents on amide wax’s solubility and the resulting gel’s structure was examined. Ethanol emerged as one of the most effective polar solvents, although optimal concentration is necessary; excessive amounts negatively affect solubility and lead to fractal gels beyond a certain concentration. Additionally, heat significantly influences activation, as higher temperatures are required for the dissolution of amide wax. Rheological curves indicate that amide wax molecules behave differently at elevated temperatures, depending on the presence of polar solvents. The study found that using an inline disperser is the most effective activation method, as it generates high shear rates to mechanically disperse the amide wax and produces heat to facilitate dissolution. Furthermore, the sagging limit of the paint film varied between 250 and 400 μm based on the activation method, despite maintaining a constant amount of amide wax. This finding suggests that optimal activation allows for achieving the desired film thickness with a reduced quantity of rheological additives.