An experimental study of the effects of topcoat on aging and fire protection properties of intumescent coatings for steel elements

摘要

This paper presents the results of an experimental study to investigate the effects of topcoat on anti-aging and fire protection properties of intumescent coatings for steel elements. Intumescent coatings with different layers of two types of topcoat were applied to steel plates. They were exposed to different cycles of hydrothermal aging before being tested in fire. The fire protection property of intumescent coatings was characterized quantitatively by effective constant thermal conductivity. A series of chemical analysis tests (DSC, FTIR and XPS) were also conducted to help understand the effects of topcoat on the degradation mechanisms of intumescent coatings. The chemical analysis test results reveal that topcoat can limit migration of hydrophilic components of intumescent coatings and therefore improve anti-aging properties of the coatings. Based on analysis of effective constant thermal conductivity, it was found that the fire protection performance of fresh intumescent coatings with 3 or 4 layers of type P (thermoplastic) topcoat was maintained throughout different cycles of aging. For type S topcoat, applying 2 layers of topcoat could almost ensure that there would be no increase in fire risk to structural safety due to aging of intumescent coatings.