Fire retardant intumescent coatings

Nenakhov, S. A. and Pimenova, V. R Physical Transformations in fire retardant intumescent coatings based on organic and inorganic compounds. PozhoFovzryvobezopasnost Fire Exp. Safety. 2011, 20(8), 17-24. 

Its usage in polymers, however, is limited by its high water solubility (10.9%) and low dehydration temperature. PPG reported the use of APB in conjunction with APP, zinc borate, silica, talc, and so on, in a flame-retardant intumescent coating for protection against hydrocarbon fires.78... 

Plastics can be protected from fire by intumescent coatings like any other substrate. However, it is well known that, generally, the present state of the art advises against such an approach, owing to technical difficulties and to economic considerations. Therefore, an alternative approach was chosen to promote intumescent behaviour in the bulk of plastics. A contributing factor was the desire to make use of the low impact on the environment and on health, typical of intumescent fire retardants. 

The srtfificient increase in fire safety of fiberglass constructions may be achieved by using the passive protection measttres—applying flame retardant intumescent coatings. 

Some of the chemicals mentioned above and others, such as chlorinated mbber or paraffin, antimony trioxide, calcium carbonate, calcium borate, pentaerythrithol, alumina trihydrate, titanium dioxide, and urea—melamine—formaldehyde resin, may be used to formulate fire retardant coatings. Many of these coatings are formulated in such a way that the films intumesce (expand) when exposed to fire, thus insulating the wood surface from further thermal exposure. Fire retardant coatings are mostly used for existing constmction. 

Certain chemicals intumesce and form a heat-insulating mat of spongy tough cells. Experiments with various fire-retardant coatings and paints indicate this to be the most effective type of protection so far developed. If the paint qualities can be improved to meet requirements for high-quality exterior paint without sacrificing any of the fire-retardant ability, there is no question of a wide market for the product. 

Stilbert and Cummings (10) describe very ably the status of fire-retardant coatings known to industry at the present time. Dow Latex 744B plasticized with Santicizer B-16 was added to a typical intumescent formulation to produce a decided improvement in the scrub resistance of the coatings, if less than 15% latex was used. 

A typical intumescent coating formulation which gives fire-retardancy is as follows ... 

Due to their low dehydration temperatures and water solubilities, boric acid and sodium borates (borax pentahydrate and borax decahydrate) are mostly used as fire retardants in wood/cellulosic products such as timbers, plywood, particle board, wood fiber, paper products, and cotton products. In recent years, boric acid has also been used as fire retardant in epoxy intumescent coating, pheno-lics, urethane foam, and so on. When necessary, boric acid can be coated with silicone oil such as silicone to alleviate its water solubility in water-based coating. 

APB solution can be sprayed on paper or the paper can be dipped into the solution to yield fire-retardant products. In addition to the cellulose, it has also been used as a flame retardant in polyurethane foam and epoxy intumescent coatings. 

Bourbigot, S., Le Bras, M., Gengembre, L. and Delobel, R. 1994. XPS study of an intumescent coating. Application to the ammonium polyphosphate/pentaerythritol fire-retardant system. Applied Surface Science 81(3) 299-307. 

The efficiency of intumescent fire retardants could be enhanced by interlayers that deliver the active components to the surface (shown by two examples). The fire-retardant additives, delivered to the surface at early stage of combustion, accelerate the formation of protecting surface layer that hinders the degradation of the underlying material. This coating structure could be reinforced by an interlayer of ceramizing capability (e.g., polyborosiloxane). Phosphorus-free intumescent fire-retardant system could be formed by using such additive. 

Apart from some specific areas such as fuel tanks or intumescent coatings, the performance in a fire test simulating a fully developed fire is often not of real interest with respect to the development of fire-retarded polymers, since common flame-retarded polymeric materials are used in applications... 

Chem. Descrip. Vinyl-toluene/acrylate emulsion copolymer Uses Resin for solv.-based coatings, waterproof texture and masonry coatings, intumescent fire-retardant paints, concrete curing membranes and sealers, paper coatings, gloss overlacquers, silk screen inks, dry electrophotographic toners... 

The INCA programme includes fire retardants for rubbers, plastics and foams, covering polyolefins, polyurethanes and other types plus expandable smoke seals, fire stop putties and sealants and intumescent coatings for metal, wood and GRP. 

EVA and Exolit AP 750 at 30% addition levels develops an intumescent coating between 200 and 460 °C to give better thermal stability and good fire retardancy. Above 460 °C, however, the protection decreases. 

Intumescence in-tu- me-son(t)s [F, fr. L intumescere to swell up, fr. in- + tumescere to swell] (ca. 1656) n. The foaming and swelling of a plastic when exposed to high surface temperatures or flames. It has particular reference to ablative urethanes used on rocket nose cones, and to intumescent coating. Kidder RC (1994) Handbook of fire retardant coatings and fire testing services. CRC Press, Boca Raton, FL. 

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