The Evolution of Intumescent Char in Flame-Retardant Coatings Based on Amino Resin

Abstract

Intumescent flame-retardant (IFR) coatings have been gaining more attention. The behaviors of intumescent char in IFR coatings play the most important role in its flame-retardant properties. However, the evolution of intumescent char throughout the whole process of protection is still unclear. In this study, both the formation and shrinkage of char were studied. The formulation of IFR includes melamine modified urea-formaldehyde resin (MUF), ammonium polyphosphate (APP) and pentaerythritol (PER). The flame-retardant properties of the coating were measured by the cone calorimeter (CONE). The evolution of the volume and the pore size distribution of char were monitored. The morphological and chemical structures were characterized by the scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that the evolution of intumescent char could be divided into three stages. More than 50% shrinkage of char occurs in the second stage. There are obvious transformations of the morphological and chemical structures of char between the different stages.

Crack-Resistant Amino Resin Flame-Retardant Coatings Using Waterborne Polyurethane as a Co-Binder Resin

“…The molten resin formed the char skeleton. Moreover, MUF decomposed and released NH 3 and CO 2 , blowing the char skeleton to form a swollen char at this stage [6,26] Tonset is the onset decomposition temperature (5% mass loss); a and b denote the weight loss rate peak of the second and third degradation stage, respectively.…”

“…There are many advantages of amino resins, such as good rigidity, high-temperature resistance, and excellent bonding performance. They can also act as the gas source in intumescent flame retardant (IFR) systems [5,6]. However, amino resin coatings typically become hard and brittle after dried, which results in the surface cracking after a few months [7].…”