Flame retardation fire retardant selection

Polymer Structure and Flammability Flame Retardation of Polymers Synergism in Flame Retardation Selection of Fire Retardants Flame Retardation of Polymeric Materials... 

Flame-retardant additives are capable of significant reduction in the ha2ard from unwanted fires, and techniques are now available to quantify these improvements. Combined with an understanding of fire-retardant mechanisms, polymer-retardant interactions, and reuse technology, formulations optimi2ed for pubHc benefit and manufacturing practicaUty can be selected. 

Silicone foam thus formed has an open ceU stmcture and is a relatively poor insulating material. Cell size can be controlled by the selection of fillers, which serve as bubble nucleating sites. The addition of quartz as a filler gready improves the flame retardancy of the foam char yields of >65% can be achieved. Because of its excellent dammabiUty characteristics, siUcone foam is used in building and constmction fire-stop systems and as pipe insulation in power plants. Typical physical properties of siUcone foam are Hsted in Table 10. 

The aim was to assess the feasibility of substitution with less hazardous flame retardants. They selected red phosphorus, ammonium polyphosphate and aluminium trihydroxide as the least environmentally problematic alternatives. Red phosphorus can technically be used in a variety of polymers to meet even the toughest fire safety standards, although it may network forall applications. ... 

The environmental impact of waste disposal and of chemical use in Europe has led to three legislative actions that, in today s global economy, greatly affect flame-retardant use and research. These actions go by the acronyms of RoHS (Reduction of Hazardous Substances), WEEE (Waste Electrical and Electronic Equipment), and REACH (Registration, Evaluation, Authorisation, and Restriction of Chemical substances). These actions are discussed in detail in Chapter 22, but need to be mentioned here as they are clear examples of how changing regulations affect flame-retardant use, selection, and new fire-safety developments. The first one, RoHS, refers to how new items are manufactured, and specifically bans chemicals and elements of environmental and toxicological concern in Europe. One fall-out item of RoHS is the move from a lead-based solder on circuit... 

New trends involve the use of nanoparticles in synthetic fibers. Polymer-layered silicates, nanotubes, and POSS have been successfully introduced in a number of textile fibers, mainly poly-amide-6, polypropylene, and polyester. Although they reduce the flammability of these fibers, but on their own are not effective enough to confer flame retardancy to a specified level. However, in presence of small amounts of selected conventional FRs (5-10 wt %), synergistic effect can be achieved. With this approach fibers having multifunctional properties can also be obtained, e.g., water repellency or antistatic properties along with fire retardancy. Most of the work in this area at present is on the lab scale and there is a potential to take this forward to a commercial scale. 

Much literature discusses the flame retardation of various polymeric materials (10-15). The techniques of reducing the flammability of polymers, in principle, are based on one or more of the three fundamental approaches described earlier. This section deals with the concept of synergism and its application in reducing flammability, selection of fire-retardant additives, and flame retarding some specific polymer systems. 

Selection of Fire Retardants. The choice of flame retardants depends on the nature of the polymer, the method of processing, the proposed service conditions, and economic considerations. Although the processing, service, and economic factors are impor.pa tant, the flame-retardancy potential of an additive is of primary importance, and this factor can be readily evaluated by thermal analysis. 

Several manufacturers or suppliers of flame retardants have listed TGA weight-loss data to facilitate the selection of appropriate fire-retardant additives. These data are reported in Table II only for those additives with identifiable structures. 

Headliners are particularly complex textile-based composites because not only do they incorporate acoustic insulative materials but they also incorporate components such as internal mirrors, interior lighting, and associated wiring - a particular fire hazard. A typical structure described by Fung and Hardcastle shows that up to seven or more component layers may be present in a modem headliner, as outlined in Table 11.11 such a structure is truly a technical textile. The whole composite must be thermoformable with individual layers bound together using adhesive films or powders. Careful selection of each component is essential if it is to pass FMVSS 302 without the need for additional flame retardant treatment. 

Another series of experiment was devoted to the selection of the most favourable construction of the least incendiary flame-retarded polystyrene foam with respect to fire protection. Sprayed asbestos wool, mortar, aluminium sheet, asbestos slate, and fibreboard were used as outer covers. 5 dm of gasoline was ignited successively in iron trays of 0.3, 0.6, and 1.0 m then an additional 10 dm in the last tray. 

In certain apphcations, flame resistance can be important. In this case, flame retarders may he added. They act hy one of four possible mechanisms. They may act to chemically interfere with the propagation of flame, react or decompose to absorb heaL form a fire resistant coating on the polymer, or produce gases that reduce the supply of air. Phosphates are an important class of flame retarders. Tritolyl phosphate and trixylyl phosphate are often used in PVC. Halogenated compounds such as chlorinated paraffins may also be used. Antimony oxide is often used in conjunction to obtain better results. Other flame retarders include titanium dioxide, zinc oxide, zinc borate, and red phosphorus. As with other additives, the proper selection of a flame retarder will depend on the particular thermoplastic. 

Modem fire protection techniques have developed through multidiscipline activities in science and engineering and involve careful selection of materials, end-use product design and manufacture, and fire performance and risk assessment. Reducing the flammability of materials is still an essential primary fire safety consideration. PP is an inherently flammable material and therefore flame retardant treatment of the polymer is an essential consideration in relation to fire safety. For material scientists, however, it is also very important to be aware of developments in fire safety science and engineering including the transition from prescriptive to functional regulation of fire safety in many coimtries. 

Phenolic composites have been the material of choice when fire safety is the main criterion for the selection of building materials. Due to the intrinsic properties of the matrix, phenolic composites do not support a flame, and when exposed to fire they produce little or no smoke, which is less toxic than the smoke produced by other composites, particularly those containing certain halogenated flame retardants (Johanson, 2005). 

Overall, the selection of appropriate flame retardant to suppress the flammability of PLA is important, especially when fire safety is needed. 

These commercial examples provide evidence that inclusion of nanoparticle species can indeed reduce the overall flame retardant additive levels required to achieve a desired fire performance level. To corroborate this, work in our laboratories ° with PA6 and PA6,6 films and selected phosphorus-containing flame retardants suggests this to be the case when selected functionalized nanoclays are also present, and this work is reviewed below. 

TAP is used as a plasticizer in flame-retardant rubber compounds because the other plasticizers provide a fuel source that feeds a fire in the case of combustion. That is why many times this phosphate plasticizer is selected instead of other plasticizers. Recently, the use of triaryl phosphates has attracted attention again because of... 

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