Fire retardant coating systems

The desired properties of the fire-retardant coating system are ... 

Fire-retardant coatings currently in use contain a number of ingredients that are either considered to be toxic heavy metals or on the hazardous air pollutants (HAPs) list. In addition, there is concern that the use of halogenated chemicals in these coatings and other products will be banned in the future. A recent paper contains the details of two reformulations programs. The first is a reformulation of a low VOC chlorinated alkyd coating and the second is a reformulation of a chlorinated emulsion system. Both programs successfully reduced the heavy metals and lowered the HAPs to an acceptable level (Dahm, 1996). 

I he words fire-retardant coatings usually imply paints or coating materials that will slow down or impede the progress of fire. The term as used here refers to a coating system that will not only prevent the progression of fire but also insulate and protect from heat the base to which the coating is applied. The base material is metal, usually aluminum. 

Chlorinated paraffins are versatile materials and are used in widely differing appHcations. As cost-effective plasticizers, they are employed in plastics particularly PVC, mbbers, surface coatings, adhesives, and sealants. Where required they impart the additional features of fire retardance, and chemical and water resistance. In conjunction with antimony trioxide, they constitute one of the most cost-effective fire-retardant systems for polymeric materials, textiles, surface coatings, and paper products. Chlorinated paraffins are also employed as components in fat Hquors used in the leather industry, as extreme pressure additives in metal-working lubricants, and as solvents in carbonless copying paper. 

The commercial samples were proposed essentially for use on interior bulkheads and the overhead. Each of the four systems employed one coat of a fire-retardant primer prior to the application of the fire-retardant top coat. 

This system, also submitted by exhibitor A, consisted of one coat of a fire-retardant red lead primer, followed by application of a fire-retardant white paint. 

In the trials within the hangar deck, a general decrease in fire-retardancy was noted as the thickness of the paint films increased from 2 to 4 top coats. This was true for all the systems tried, except for No. 8 which retained its fire-retardancy even at a film thickness of 5.5 mils. This general decrease in fire-retardancy with increase in film thickness is in line with normal expectations. System 1, the standard fire-retardant... 

Panels of 24-ST alclad aluminum, 6x6 inch 0.032 sage, are coated with the fire-retardant system (only one surface) and placed in the vibrating test rig. 

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. 

Biological methylation of antimony has not been demonstrated directly by use of experimental organisms. However, methylstibonic acid and dimethylstibinic add were found in fact in marine and estuarine environment . There is no obvious thermodynamic barrier to biomethylation. The chemical similarity between Sb and Sn, Pb, As, Se and Te, which surround Sb in the periodic table, and all of which have been shown to be subject to biomethylation, would suggest the existence of a biomethylation pathway also for antimony. This possibility assumes importance when the current extensive use ca 2 X lO kgy" in United State and ca lO kgy in Japan) of inorganic and organic antimony compounds in conjunction with halocarbons in fire retardant systems is considered. Products containing antimony-hased fire retardant systems include textiles, plastics, elastomers, paper, wood, paints and coatings. ... 

Future Research. Improvements in leach-resistant chemicals have been a primary concern over the past decade. Advances have been made in leach-resistant systems such as the amino-resin systems however improvements still need to be made in leach-resistant compounds without increasing the cost. Other areas where research on fire retardants needs to be conducted are in coating systems, especially those that are durable to weathering and UV degradation reduction of smoke and toxic products, improvements in fire-retardant treatments for panel products and fundamental work on the mechanisms of particular formulations. 

The fire-retardant mechanism associated with nanoclays has recently been studied and is likely to involve the formation of a ceramic skin which catalyzes char formation by thermal dehydrogenation of the host polymer to produce a conjugated polyene structure. " The nanocomposite structure present in the resulting char appears to enhance the performance of the char through reinforcement of the char layer. These effects would explain the apparent fire-retardant synergy observed when nanoclays are incorporated into polymer formulations containing condensed phase fire-retardant systems, including coated fillers. 

Manufacturers of various fillers continue studies on altemative systems. Most antimony oxide used as a fire retardant can be replaced by a combination of zinc borate without the loss of other properties (in some cases improvements are reported). Another option is to use the same filler systems which are used in polyethylene insulated cables and wires. These are based on magnesium hydroxide and aluminum hydroxide. These systems pcrfoim as flame retardants but require a high filler concentration which affects jacket resistance and mechanical performance. Recently, new coated grades have been developed which can be used at up to 65 wt% without the loss of properties or productivity (extrusion rates 2,500 m/min of cable are possible). ... 

Hexabromocyclododecane Saytex 60006L Saytex BCT-610 Saytex HBCD-LM. Fire retardant for wide range of plastics, textiles, adhesives, and coatings esp. for styrene-based systems. Solid mp 188-191 d = 2.36 soluble in common solvents LDso (rat orl) >10,000 mg/kg, (rbt dermal) >10,000 mg/kg. Amerihaas Dead Sea Bromine Great Lakes Fine Chem. 

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