Typical expansion ratios are about 50:1, i.e. Thin film intumescents have the added advantages that they can easily cover complex shapes and post-protection service installation is relatively simple. If a decorative or bespoke finish is required, this should be included in the specification. Solvent-based materials also tend to be able to cover a wider range of section factors than water-based materials and can be used on-site to protect smaller sections requiring high thicknesses.īoth solvent-based and water-based coatings can be used to achieve attractive surface finishes. For more aggressive environments, solvent-based products are commonly applied. In general, for structures in a C1 environment (dry internal steelwork), most on-site application is carried out using water-based materials. They can be applied either on-site or off-site. In recent years, a number of products have been developed which can provide 120 minutes fire resistance. Thin film intumescent coatings are mainly used in buildings where the fire resistance requirements are 30, 60 and 90 minutes. The production of these gases causes the carbonaceous char to swell or foam and expand to provide an insulating layer many times the original coating thickness. These gases include carbon dioxide, ammonia and water vapour. A spumific agent which decomposes together with the melting of the binder, to liberate large volumes of non-flammable gases.A binder or resin which softens at a predetermined temperature.A carbonific such as starch which combines with the mineral acid to form a large volume of carbonaceous char.A catalyst which decomposes to produce a mineral acid such as phosphoric acid.The basecoat usually comprises the following ingredients: Thin film intumescent coating systems generally have three components, a primer, a basecoat (the part which reacts in the fire) and a sealer coat. Thick film intumescent coatings were originally developed for the off-shore and hydrocarbon industries but have been modified for use in buildings. Thin film materials are either solvent-based or water-based and are mainly used to protect building structures. Intumescent coatings can be divided into two broad families: thin film and thick film. As a result of this reaction the coatings swell and provide an expanded layer of low conductivity char. At these temperatures the properties of steel will not be affected. Intumescent coatings are paint-like materials which are inert at low temperatures but which provide insulation as a result of a complex chemical reaction at temperatures typically of about 200-250☌.
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