Vitreous fillers in intumescent coatings

The introduction of vitreous fillers in some intumescent coatings compositi ons proved to be useful both in improvement of thermal insulation and durab ility of char under fire and in smoke emission characteristics. In this pap er a comprehensive experimental study is presented showing results for solv ent-borne, 2K epoxy and water-borne intumescent paints. Blends of vitreous fillers with different melting temperatures, between 350 degrees C and 850 degrees C, have been tested together with refractory fil lers (with melting temperatures between 1100 degrees C and 1350 degrees C). Lead free vitreous fillers with very low melting temperatures (from 350 de grees C to 550 degrees C) and with low water solubility were developed. Dif ferent types of paints have been prepared by adding different amounts of vi treous fillers. These compositions were then fire tested after application on steel plates. The effect of vitreous fillers on fire performance and sta bilization of char (by means of encapsulation, with or without self-extingu ishing additives) has been studied. The fillers' effect on smoke emission u nder fire was also examined both in terms of optical density and toxicity i ndex. A special attention was focused on water-borne intumescent paints modified with vitreous fillers of different solubility and melting temperature. Resi dual solubility of the vitreous fillers, which appeared as a very important parameter for paint stability, has been assessed. Vitreous fillers releasi ng alkaline ions in such an amount to give a conductivity higher than 500 m u S cm, make the intumescent paint composition unstable. (C) 1999 Elsevier Science S.A. All rights reserved.