Correlations of rheological methods to coatings' performance

Most basic issues of organic coatings are related to rheology. The paper extracts rheological methods from the references to establish correlations with coating performance, which sets a framework for coating rheology. The low-frequency parameters obtained in oscillatory tests can be used to predict rheological properties in very slow processes, such as pigment settlement and sagging. Fractal analysis is used to investigate pigment flocs in coatings, but the affinity of medium to pigment particles determines whether fractal structures of flocs form and which formation mechanism to take. During curing processes, an increase in storage modulus G′ and a decrease in the inclination of G′-ω plots are used to measure and indicate crosslink density. The product of intrinsic viscosity and boundary concentration where polymer coils start to entangle, C∗[η], regardless of the molecular weight, is used to assess the chain configuration in polymer solutions. Extensional viscosity and the elastic modulus in nonlinear regime are used to investigate roll spatter and spray atomization. The sagging and levelling performance of coatings can be characterized by the empirical Leneta flow test, simple 3ITT, and quantitative falling wave method. Stress ramp loop can be used to directly measure static yield stress and identify the formation mechanism of fractal structures, revealing internal change within coatings. Rheology modifiers are introduced in detail.