Fire resistance, intumescent coating

Few recent scientific papers are devoted to resistance to fire using intumescent coating, but a growing market for this application exists. A rapid survey of the literature shows that the formulations used are always based on the well-known trio APP/PER-Melamine. Nevertheless a lot of work remains to be done to understand and to quantify the mechanisms of intumescence acting as protective heat barrier. 

These coatings provide the most effective fire-resistant system available but originally were deficient in paint color properties. Since, historically, the intumescence producing chemicals were quite water-soluble, coatings based thereon did not meet the shipping can stability, ease of application, environmental resistance, or aesthetic appeal required of a good protective coating. 

Carbonaceous char barriers may be formed by the normal mode of polymer burning, and besides representing a reduction in the amount of material burned, the char may act as a fire barrier. The relationship of char yield, structure, and flame resistance was quantified by Van Krevelen (5) some years ago. For polymers with low char-forming tendencies, such as polyolefins, one approach to obtain adequate char is to add a char-forming additive. Such additives generally bear a resemblance to intumescent coating ingredients (6, 7). 

Passive protection can be used to increase the time to structural failure. For example, intumescent mastic coatings of less than 1 inch thickness have been shown to provide up to 4 hours of fire resistance when applied to steel columns. Cementitious materials have been shown to provide 1-4 hours fire resistance for thicknesses of 2.5-6.3 cm (1-2.5 in). For additional information on passive fire protection, see Chapter 7. 

At an optimum addition level of only 1.5 w t %, nano-size magnesium-aluminum LDHs have been shown to enhance char formation and fire-resisting properties in flame-retarding coatings, based on an intumescent formulation of ammonium polyphosphate, pentaerythritol, and melamine.89 The coating material comprised a mixture of acrylate resin, melamine formaldehyde resin, and silicone resin with titanium dioxide and solvent. It was reported that the nano-LDH could catalyze the esterification reaction between ammonium polyphosphate and pentaerythritol greatly increasing carbon content and char cross-link density. 

Kobayashi, N., Yoshida, K., Sagawa. K., and Ishibara, S. 1995. Intumescent fire resistant coating, fire resistant material, and process. U.S. Patent, 5,401,793. 

The development of the midspan defection of the GFRP profile with intumescent coating is shown in Figure 9.3 and compared to the ones with or without fire protections. The GFRP profiles incorporated with intumescent coating and cementitious mortar demonstrated similar time-dependent deformation responses and further showed very similar fire resistance times (76 min vs 74 min). However, the former... 

It is difficult to achieve a fire resistance rating with just composite protective systems. However, fire resistance and reduced smoke and toxicity can be achieved by the use of fire barriers which include ceramic fabric, ceramic coatings, intumescent coatings, or... 

A new US company based in Hudson, Massachusetts has developed intumescent coatings and additives that enhanee the fire properties of plastic and composite structures. Avtec Industries now offer Thermashield mastic coatings that can withstand temperatures in excess of 1200 °C for sustained periods. The coatings material is non-toxic and does not flake, peel or chip. It is resistant to water and chemieal attack and is claimed to withstand multiple high-impact shocks. 

Many types of coating are available which exhibit varying degrees of chemical resistance, durability and ease of application. Intumescent coatings are also used in the repair of fire damaged structures. Some of the more widely used products are bituminous coatings and mastics, polyesters and vinyl esters, PU, EP, polychloroprene, coal tar, acrylics, and so on [281]. 

Wang ZY, Han EH, Ke W. Fire-resistant effect of nanoclay on intumescent nanocomposite coatings. J Appl Polym Sci February 2007 103(3) 1681-9. 

Several additional compounds may be added to the basic components to improve fire protection in intumescent coating formulations. For example, vitrifying agents can increase the thermal resistance of the intumescent char, whereas nucleating additives can help to control cell size in the char [1,2]. 

As a result, carbon-metal-containing multiwall nanotubes and as-tralenes are obtained. Depending upon the conditions nanoproducts can be metallic nanoparticles and nanowires in carbon shells. The yield of nanoproducts, calculated on carbon of PVA, is about 80-90%. The nanoproducts obtained can be applied as additives (0.01-0.05%) to improve the properties of foam concrete and intumescent fire-resistant coatings whose characteristics improve in 2-3 times. 

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