Fire-retardant 56 Interference

Metal hydrates such as aluminium trihydrate or magnesium hydroxide remove heat by using it to evaporate water in their structures, thus protecting polymers. Bromine or chlorine-containing fire retardants interfere with the reactions in flames and quench them. Mixtures of flame retardants antimony trioxide and organic bromine compounds are more effective at slowing the rate of burning than the individual flame retardants alone. 

In order to produce lignocellulosic-based engineering materials with a long service life, it is necessary to interfere with the natural degradation processes for as long as possible. This can be done in several ways. Traditional methods for decay resistance and fire retardancy, for example, are based on treating... 

The sueeess of graphite in this applications shows that filler with plate like struetures should be considered when intumescent materials are being formulated. Reeent developments in intumescent paints show that performanee ean be improved if a layer of organic material is inserted between the layers of the plate like filler. The degradation of this material in the enclosed space increases the expansion rate and the retention of gas inside the degrading material. Based on this prinei-ple any plate like filler has the potential to be useful in an intumescent applieation. The eomposition of filler is also important. When clay was used as a filler in fire retardant applieations, it was found that some of its components interfere with the action of carbonization catalysts and detract from the overall performance of the system in terms of limiting oxygen index. ... 

Depending on the polymer and the applicable fire retardance standards, flame retardants are chosen to interfere with one or more stages ofthe combustion process heating, decomposition, ignition, flame spread, and smoke density. Fire retardants have to inhibit or even suppress the combustion process. 

Presence of preservatives. Creosote oil, provided it is not present to excess so that it appears on the surface of freshly machined or sanded wood before the adhesive is applied, is not deleterious to R/F or P/F adhesives. Timber preservatives based on pentachlorophenol or tin, even if up to 1% wax has been added, do not influence these materials. Fire retardants based on ammonium salts may interfere with the cross-linking R/F and P/F adhesives such that recommended periods of cure may have to be extended. M-U/F adhesives are adversely affected if wax is added with the preservative. 

Overdrying should be avoided as it can force hydrophobic extractives that can interfere with bonding to the surface (especially for resinous species) or can close some of the natural pores. Preservatives and fire retardants can also serve to fill natural pores and reduce the opportunities for good bond formation. 

Some small molecules exert a profound influence on the mode of decomposition of PMMA. Silver acetate has been found to greatly accelerate depolymerization zinc bromide changes the entire character of the degradation reaction, with the formation of various volatile products, notably methyl bromide. The fire retardant additive ammonium polyphosphate acts by reaction with the polymer so as to interfere with the monomer-producing reaction. ... 

Solid (Condensed) Phase Sohd phase fire retardant(s) alter the physical burning characteristics by either forming an insulative fire barrier or by changing the surface morphology to interfere with the release or generation of combustible gases. This mechanism is commonly seen with phosphorus-based flame retardants. 

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. 

In the gas phase, the process of combustion is slowed down by reactive species that interfere chemically with the propagation process of the fire. The flame retardants... 

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