Vitreous fillers in intumescent coatings

The introduction of vitreous fillers in some intumescent coatings compositions proved to be useful both in improvement of thermal insulation and durability of char under fire and in smoke emission characteristics. In this paper a comprehensive experimental study is presented showing results for solvent-borne, 2K epoxy and water-borne intumescent paints.

Blends of vitreous fillers with different melting temperatures, between 350°C and 850°C, have been tested together with refractory fillers (with melting temperatures between 1100°C and 1350°C). Lead free vitreous fillers with very low melting temperatures (from 350°C to 550°C) and with low water solubility were developed. Different types of paints have been prepared by adding different amounts of vitreous fillers. These compositions were then fire tested after application on steel plates. The effect of vitreous fillers on fire performance and stabilization of char (by means of encapsulation, with or without self-extinguishing additives) has been studied. The fillers’ effect on smoke emission under fire was also examined both in terms of optical density and toxicity index.

A special attention was focused on water-borne intumescent paints modified with vitreous fillers of different solubility and melting temperature. Residual solubility of the vitreous fillers, which appeared as a very important parameter for paint stability, has been assessed. Vitreous fillers releasing alkaline ions in such an amount to give a conductivity higher than 500 μS cm, make the intumescent paint composition unstable.