On the stratification mechanism of self-stratifying epoxy-acrylic coatings

To shed light on the self-stratification mechanism in epoxy-acrylic coatings, 200-, 400-, and 800-micron-thick coatings were applied on glass and aluminum substrates, and their solidification behavior was studied. Some of the applied coats showed self-stratification behavior, with the thermoplastic acrylic copolymer in the top layer. In addition, experiments were performed on epoxy-acrylic solutions without hardeners to evaluate the resulting convective patterns on the solution surface, which exhibited finger-type convection. The final structure of the films had an apparent dependency on the thickness. Thicker films were usually more stratified and had a thicker stratified layer. As these observations could not support diffusion as the primary mechanism of self-stratification, convection experiments were done on epoxy and coatings solutions. The surface patterns on the solutions were studied, and the finger-type convection was observed. Based on these observations, we propose that convection may be the primary movement mechanism rather the diffusion of polymers toward the surface in the self-stratifying coats.

Automated summary

The study on epoxy-acrylic coatings reveals that self-stratification is primarily driven by convection rather than diffusion. Thicker films tend to exhibit more prominent stratification with a thicker stratified layer.