Flame retardants selection

Other flame-retardants selected as priority chemicals for the EU Risk Assessment process included tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), tris(2-chloroethyl) phosphate (TCEP), tris (2-chloropropyl) phosphate (TCPP), tris(2-chloro-l-(chloromethyl)ethyl) phosphate (TDCP), and 2,2-bis(chloromethyl) trimethylene bis (bis(2-chloroethyl)phosphate) (V6). The flame-retardant synergist, antimony trioxide (Sb ), was also identified as a priority substance. Table 22.1 contains information on the EU Risk Assessments on the nine flame-retardants and one synergist. 

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

The primary concern when selecting a flame retardant for a given application is that it is effective to the extent required for the application. The end-use application will often determine the flame retardant selected. Assessment is made by exposing samples of the final formulation to a series of tests. 

In order to improve the heat stability and thereby eliminate or minimize thermal decomposition during molding, the flame retardant high temperature PA formulations may further comprise finely divided calcium oxide. The amount of calciiun oxide necessary to effect improvement in the heat stability may depend in part upon the particular PA employed, as well as upon the particular combination of antimony oxide and halogen containing flame retardant selected. 

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. 

In selecting a flame retardant for a given appHcation, the cost contribution of the flame retardant to the final polymer compound must be taken into account. Assessment of cost should be done on a cost per volume basis rather than a simple cost per weight basis. 

Ra.dia.tlon. Use of radiation to affect fixation of some flame retardants is being investigated (110). Electron-beam fixation requires the selection of compounds that can be insolubilized inside or outside of the fiber with high yield in a short time. Polyunsaturated compounds, eg, Fyrol 76, have shown promise (see Radiation curing). 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

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. 

Principles and Characteristics Combustion analysis is used primarily to determine C, H, N, O, S, P, and halogens in a variety of organic and inorganic materials (gas, liquid or solid) at trace to per cent level, e.g. for the determination of organic-bound halogens in epoxy moulding resins, halogenated hydrocarbons, brominated resins, phosphorous in flame-retardant materials, etc. Sample quantities are dependent upon the concentration level of the analyte. A precise assay can usually be obtained with a few mg of material. Combustions are performed under controlled conditions, usually in the presence of catalysts. Oxidative combustions are most common. The element of interest is converted into a reaction product, which is then determined by techniques such as GC, IC, ion-selective electrode, titrime-try, or colorimetric measurement. Various combustion techniques are commonly used. 

In order to accomplish with the aforementioned aim, during the first year of project, an extensive research on the different chemical additives used in six industrial sectors was conducted plastics, textiles, electronics, lubricants, leather, and paper. A list of selected chemical additives was identified for each sector and used as a study basis for the rest of the project. This is the case of the decabromo-diphenyl ether (BDE) used in electronics as a flame retardant or the triclosan used in the textile as a biocide. The results of this investigation were presented in the first volume of this book (Global Risk-Based Management of Chemical Additives I Production, Usage and Environmental Occurrence). This volume also included a section of case studies related to the selected additives in different countries (i.e., Denmark, Vietnam, Brazil, India). The main outcomes of the first part of the project are summarized below ... 

In flame retarding nonwovens, the contribution of components may not be additive. Rather, the interaction of binder, flame retardant, and substrate is critical in the performance of the flame retardant nonwoven. Similarly, the flammability of a binder film or the flammability of a flame retardant coated woven cloth often do not predict the flame retardancy of the same binder or flame retardant on a nonwoven substrate of rayon or polyester. Actual data on a nonwovens substrate is the only accurate measure of a system s flame retardancy. For this study, two widely used substrates were selected. The first, lightweight rando rayon, is representative of material used in nurse caps, surgeon s masks, and miscellaneous coverstock. This material is constructed of 1 1/2 denier fiber, weighs 1 1/2 ounces per square yard, and is relatively dense web. Rayon as a material is water absorbent, burns rather than melts, and is readily flammable. This fiber ignites around 400°C(2) and has an oxygen index of about 19.0. Certain binders adhere well to rayon while others do not. Apparently, this lack of affinity for the substrate affects flame retardancy, as will be demonstrated later. 

Table III. Selected Dow Chemical Patents on Flame Retardants for Polycarbonates...

Toxicological Risks of Selected Flame-Retardant Chemicals (2000)... 

In order to determine the sources of contamination, some water samples, including wastewaters and effluents from different industries were also sampled. Along the Cinca River and in the industrial area of Monzon, industrial effluents from two different industries were selected the first one produced EPS (Expandable polystyrene) treated with flame retardants and ABS (Acrylonitrile-butadiene-styrene), and the second one produced PVC (Polyvinyl chloride). As regards the Vero River, three industries were sampled the first one, a textile industry which produced polyester fibers treated with flame retardants, the second one produced epoxy... 

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