Nano-clay filled polyester coatings

Polyester composite coatings were produced by mixing un-saturated polyester (HP) resin and functionalized montmorillonite (MMT) powder. The effect of the mixing conditions on the final performances of the composite coatings was accurately evaluated: samples were produced with different MMT contents (up to 5 wt%) and stirring time (up to 1200 min). Rheological analyses of the un-catalyzed resin matrix were performed as well as tribological and scratch tests of coatings. Results show the strong effect of the mixing time on the performance of the MMT filled coatings. This effect is never negligible and can overcome the effect of the MMT content. After 20 h mixing, a 1 wt% filled mixture reaches a viscosity similar to a 5 wt% mixture after 30 min. By increasing the resin viscosity, the resulting coating thickness increases as well and this effect seems to dominate the tribological behavior of coatings rather than it's filling. Best results were obtained with low mixing times and filler contents.