Chemical impregnation, fire retardants

The surface burning characteristics (flame spread index and smoke developed index) for wood and wood products as measured by American Society for Testing and Materials (44) can be reduced with fire retardant treatments, either chemical impregnation or coatings (48). Fire retardant treatments also reduce the heat release rate of a burning piece of wood (49,50). The heat release rates (51) of the burning materials are an important factor in fire growth. 

Solutions of these fire retardant formulations are impregnated into wood under fliU cell pressure treatment to obtain dry chemical retentions of 65 to 95 kg/m this type of treatment greatly reduces flame-spread and afterglow. These effects are the result of changed thermal decomposition reactions that favor production of carbon dioxide and water (vapor) as opposed to more flammable components (55). Char oxidation (glowing or smoldering) is also inhibited. 

Flameproof (or Fireproof) Compounds are substances used to impregnate various flammable materials to make them fire-resistant or capable of burning without flame. Numerous compns are given in Refs 1 2. (See also Fire-Resistant Textiles and Fire-Retardant Paints) Refs 1) H. Bennet, "The Chemical Formulary , Vol 1-7, Van Nostrand, NY(1933—... 

How does our research stand in rendering wood fire retardant What is the effect of fire-retardant treatments on the fire performance properties of wood and on the physical and mechanical properties of wood that are important to its utility Discussion will be limited to fire retardancy obtained by pressure impregnation, which is currently the most effective method. Fire-retardant coatings, wood-plastic combinations, and chemical modifications of wood will not be considered. 

The success of this treatment system indicated a breakthrough in the development of a commercially successful system whereby fire-retardant chemicals are pressure impregnated into the wood and fixed or converted to a leach-resistant state without serious impairment of the desirable natural wood properties. This development has stimulated research with leach-resistant type treatments. Chemicals employed usually involve organic phosphates and compounds that can react with phosphorous-containing chemicals or with the wood cellulose structure to give permanence of treatment. 

Most fire-retardant formulations are not resistant to leaching by water. Therefore, there have been increased efforts to develop leach-resistant chemicals that can be impregnated into wood products for use in exterior or high humidity applications. Some of the proposed leach-resistant systems include chemical combinations that form insoluble complexes, amino-resin systems, and monomers that polymerize in the wood. 

Treated lumber- A wood product which has been impregnated with chemical pesticides such as CCA (Chromated Copper Arsenate) to reduce damage from wood rot or insects. Often used for the portions of a structure which are likely to be in contact with soil and water. Wood may also be treated with a fire retardant. 

Wood surfaces can be chemically inactivated by external contamination and selfcontamination. External contamination results from airbome chemical contaminants, oxidation and pyrolysis of wood bonding surface from overdrying or exposure to high temperatures, impregnation with preservatives, fire retardants, and other chemicals. Self-contamination results from a natural surface inactivation process where the hydrophobic wood extractives might migrate with time to the wood surface and affect adhesion. 

Behind this chemical resistant layer, the loadcarrying laminate was constructed. This layer was spread on the basis of alternating layers strand mat M 510 and RT 310, impregnated with epoxy based vinyl ester resins DION-9700. Thickness of a power layer was 9.0 mm. The external fire-resistant layer consists of alternating layers glass-fabric RT- 490 and RT-310, impregnated with fire retardant resin of mark POLILATE 850-840. The mass maintenance of resin in FRP was 46.5 %, volumetric - 63.4 %. 

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