Additives flame retardant functions

The use of copolymers is essentially a new concept free from low-MW additives. However, a random copolymer, which includes additive functions in the chain, usually results in a relatively costly solution yet industrial examples have been reported (Borealis, Union Carbide). Locking a flame-retardant function into the polymer backbone prevents migration. Organophosphorous functionalities have been incorporated in polyamide backbones to modify thermal behaviour [56]. The materials have potential for use as fire-retardant materials and as high-MW fire-retardant additives for commercially available polymers. The current drive for incorporation of FR functionality within a given polymer, either by blending or copolymerisation, reduces the risk of evolution of toxic species within the smoke of burning materials [57]. Also, a UVA moiety has been introduced in the polymer backbone as one of the co-monomers (e.g. 2,4-dihydroxybenzophenone-formaldehyde resin, DHBF). 

The compatibility of a colorant is assessed not only on the basis of the ease with which it can be mixed with the base resin to form a homogeneous mass but also on the requirement that it neither degrades nor is degraded by the resin. In relation to product functional properties, incompatibihty of a colorant can affect mechanical properties, flame retardancy, weatherability, chemical and ultraviolet resistance, and heat stability of a resin through interaction of the colorant with the resin and its additives. Flame retardancy, for example, may impinge directly on the performance of a colorant. Pressure to produce materials with lower levels of toxic combustion products can involve organic fire retardant additives that interact with the colorant either to negate the effect of the additives or affect the color. 

Flame-retardant textiles are textiles or textile-based materials that inhibit or resist the spread of fire. Factors affecting flammability and thermal behavior of textile include fiber type, fabric construction, thermal behavior of textile polymer and its composition as well as the presence or absence of flame additives. On the other hand, flame-retardant additives can be classified by their chemical composition or by mode of action, i.e., gas phase action or by the formation of protective barrier [49, 50]. Moreover, flame-retardant functional finishes of cellulose-based textiles can be accomplished by [i] using inorganic phosphates, (ii) with organophosphorous compounds, [iii) with sulfur-derivatives or (iv) by grafting flame retardants monomers [49,50]. 

Within the area of textiles, coatings and back-coatings are applied either to confer a level of flame retardancy alone or as an additional flame retardant property to another coating function such as water repellenqr, for example. 

Fluorine is more effective as an inherent flame retardant in the basic polymer than as a reactive flame retardant or additive flame retardant employed in later stages of the product. As part of the basic polymer, it functions essentially in the condensed phase. It is effective in the stages of decomposition and ignition, and increases the possibility of arresting the burning process at an... 

The most important fluorine-containing compounds which function as additive flame retardants are the chlorofluorocarbons, which contribute to fire resistance when used as blowing agents in polyurethane and polystyrene foams. 

Useful materials incorporating fire-retardant additives are not always straightforward to produce. Loadings of 10% are common, and far higher levels of flame retardants are used in some formulations. These concentrations can have a negative effect on the properties and functions for which the materials were originally intended. Product-specific trade-offs are generally necessary between functionaUty, processibiUty, fire resistance, and cost. 

In order for a soHd to bum it must be volatilized, because combustion is almost exclusively a gas-phase phenomenon. In the case of a polymer, this means that decomposition must occur. The decomposition begins in the soHd phase and may continue in the Hquid (melt) and gas phases. Decomposition produces low molecular weight chemical compounds that eventually enter the gas phase. Heat from combustion causes further decomposition and volatilization and, therefore, further combustion. Thus the burning of a soHd is like a chain reaction. For a compound to function as a flame retardant it must intermpt this cycle in some way. There are several mechanistic descriptions by which flame retardants modify flammabiUty. Each flame retardant actually functions by a combination of mechanisms. For example, metal hydroxides such as Al(OH)2 decompose endothermically (thermal quenching) to give water (inert gas dilution). In addition, in cases where up to 60 wt % of Al(OH)2 may be used, such as in polyolefins, the physical dilution effect cannot be ignored. 

Inert Gas Dilution. Inert gas dilution involves the use of additives that produce large volumes of noncombustible gases when the polymer is decomposed. These gases dilute the oxygen supply to the flame or dilute the fuel concentration below the flammability limit. Metal hydroxides, metal carbonates, and some nitrogen-producing compounds function in this way as flame retardants (see Flame retardants, antimony and other inorganic compounds). 

TrialkylPhosphates. Triethyl phosphate [78-40-0] C H O P, is a colorless Hquid boiling at 209—218°C containing 17 wt % phosphoms. It may be manufactured from diethyl ether and phosphoms pentoxide via a metaphosphate intermediate (63,64). Triethyl phosphate has been used commercially as an additive for polyester laminates and in ceHulosics. In polyester resins, it functions as a viscosity depressant as weH as a flame retardant. The viscosity depressant effect of triethyl phosphate in polyester resins permits high loadings of alumina trihydrate, a fire-retardant smoke-suppressant filler (65,66). 

Environmental Considerations. The phosphate flame retardants, plasticizers, and functional fluids have come under intense environmental scmtiny. Results pubUshed to date on acute toxicity to aquatic algae, invertebrates, and fish indicate substantial differences between the various aryl phosphates (159—162). The EPA has summarized this data as well as the apparent need for additional testing (147). 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

A multidimensional system using capillary SEC-GC-MS was used for the rapid identification of various polymer additives, including antioxidants, plasticizers, lubricants, flame retardants, waxes and UV stabilizers (12). This technique could be used for additives having broad functionalities and wide volatility ranges. The determination of the additives in polymers was carried out without performing any extensive manual sample pretreatment. In the first step, microcolumn SEC excludes the polymer matrix from the smaller-molecular-size additives. There is a minimal introduction of the polymer into the capillary GC column. Optimization of the pore sizes of the SEC packings was used to enhance the resolution between the polymer and its additives, and smaller pore sizes could be used to exclude more of the polymer... 

Chemical pretreatments with amines, silanes, or addition of dispersants improve physical disaggregation of CNTs and help in better dispersion of the same in rubber matrices. Natural rubber (NR), ethylene-propylene-diene-methylene rubber, butyl rubber, EVA, etc. have been used as the rubber matrices so far. The resultant nanocomposites exhibit superiority in mechanical, thermal, flame retardancy, and processibility. George et al. [26] studied the effect of functionalized and unfunctionalized MWNT on various properties of high vinyl acetate (50 wt%) containing EVA-MWNT composites. Figure 4.5 displays the TEM image of functionalized nanombe-reinforced EVA nanocomposite. 

More recently, the same author [41] has described polymer analysis (polymer microstructure, copolymer composition, molecular weight distribution, functional groups, fractionation) together with polymer/additive analysis (separation of polymer and additives, identification of additives, volatiles and catalyst residues) the monograph provides a single source of information on polymer/additive analysis techniques up to 1980. Crompton described practical analytical methods for the determination of classes of additives (by functionality antioxidants, stabilisers, antiozonants, plasticisers, pigments, flame retardants, accelerators, etc.). Mitchell... 

Since flame retardants have been recognized as not desirable (although not properly quantified in economic valuation), there is now work on replacing flame retardants with other additives with the same functionality. 

PMMA - Red Phosphorus System. The initial reaction that was investigated was that between PMMA and red phosphorus (4-51. Phosphorus was chosen since this material is known to function as a flame retardant for oxygen-containing polymers (1 2). Two previous investigations of the reaction of PMMA with red phosphorus have been carried out and the results are conflicting. Raley has reported that the addition of organic halides and red phosphorus to PMMA caused moderate to severe deterioration in flammability characteristics. Other authors have reported that the addition of chlorine and phosphorus compounds are effective flame retardant additives (12). 

Char formation and reduced monomer production are observed for all of these additives upon reaction with PMMA. Char formation increases as a function of temperature, for the hydrido cobalt compound, there is 5% char at 262°, 8.5% at 322°, 15% at 338°, and 19% at 375°C the cobalt(lll) cyanide produces 3% char at 338° and 11% at 375°C the cobalt(ll) cyanide yields 11% char at 375°C. At the highest temperature, 375°C, the amount of monomer formation is 22% for K3Co(CN)5, 11% for K3Co(CN)6, and 10% for HCo[P(OPh)3]4. Ideally one would hope to observe no monomer formation and complete char production. Such is not the case here, these materials probably have no utility as flame retardant additives for PMMA since monomer formation, even at a reduced level, will still permit a propagation of the burning process. While somewhat positive results for these three additives do not prove the validity of the hypothesis, we take this to be a starting point in our search for suitable additives, further work is underway to refine the hypothesis and to identify other potential hydrogenation catalysts and other additives that may prove useful as flame retardants for PMMA... 

The dynamic mechanical behavior of most homogeneous and heterogeneous solid and molten polymeric systems or composite formulations can be determined by DMA. These polymeric systems may contain chemical additives, including fillers, reinforcements, stabilizers, plasticizers, flame retardants, impact modifiers, processing aids, and other chemical additives, which are added to the polymeric system to impart specific functional properties and which could affect the process-ability and performance. 

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