Flame-retarded matrices

Ammonia—Gas-Cured Flame Retardants. The first flame-retardant process based on curing with ammonia gas, ie, THPC—amide—NH, consisted of padding cotton with a solution containing THPC, TMM, and urea. The fabric was dried and then cured with either gaseous ammonia or ammonium hydroxide (96). There was Httle or no reaction with cellulose. A very stable polymer was deposited in situ in the cellulose matrix. Because the fire-retardant finish did not actually react with the cellulose matrix, there was generally Httle loss in fabric strength. However, the finish was very effective and quite durable to laundering. 

Thermosetting unsaturated polyester resins constitute the most common fiber-reinforced composite matrix today. According to the Committee on Resin Statistics of the Society of Plastics Industry (SPl), 454,000 t of unsaturated polyester were used in fiber-reinforced plastics in 1990. These materials are popular because of thek low price, ease of use, and excellent mechanical and chemical resistance properties. Over 227 t of phenoHc resins were used in fiber-reinforced plastics in 1990 (1 3). PhenoHc resins (qv) are used when thek inherent flame retardance, high temperature resistance, or low cost overcome the problems of processing difficulties and lower mechanical properties. 

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... 

Incineration of a collection of polymers with 10 different kinds of brominated flame retardants has been studied under standardized laboratory conditions using varying parameters including temperature and air flow. Polybrominated diphenyl ethers like the deca-, octa-, and pentabromo compounds yield a mixture of brominated dibenzofurans while burning in polymeric matrices. Besides cyclization, debromination/hydrogenation is observed. Influence of matrix effects and burning conditions on product pattern has been studied the relevant mechanisms have been proposed and the toxicological relevance is discussed. 

It can be seen from Figure 5 that the amount of the added synergist Sb203 of the flame retardant strongly effects the PBDF yield and the optimal temperature of PBDF formation. The kind of polymeric matrix itself does not effect yields of PBDF. 

Figure 8.2 Excerpt from the US ERA Eurniture Flame Retardants Hazard Assessment Matrix. Reproduced with permission of Clive Davies, US Environmental Protection Agency.

Brandt [200] has extracted tri(nonylphenyl) phosphite (TNPP) from a styrene-butadiene polymer using iso-octane. Brown [211] has reported US extraction of acrylic acid monomer from polyacrylates. Ultrasonication was also shown to be a fast and efficient extraction method for organophosphate ester flame retardants and plasticisers [212]. Greenpeace [213] has recently reported the concentration of phthalate esters in 72 toys (mostly made in China) using shaking and sonication extraction methods. Extraction and analytical procedures were carefully quality controlled. QC procedures and acceptance criteria were based on USEPA method 606 for the analysis of phthalates in water samples [214]. Extraction efficiency was tested by spiking blank matrix and by standard addition to phthalate-containing samples. For removal of fatty acids from the surface of EVA pellets a lmin ultrasonic bath treatment in isopropanol is sufficient [215]. It has been noticed that the experimental ultrasonic extraction conditions are often ill defined and do not allow independent verification. 

In order to validate sliding spark spectrometry results, plastic material was collected and the element concentration was determined via AAS after digestion. The samples were used as calibration standards. Additional standards were obtained by manufacturing known amounts of additives in the polymer matrix. Calibrations were made for Cd, Cr, Pb, Zn, Sb, Si and Ti in chlorine-free polymers Al, Ba, Ca, Cd, Pb, Sn, Ti, Zn in PVC chlorine (as PVC) and bromine in polyurethane (PUR). A calibration curve for Br as a flame retardant in PUR is shown in Figure 8.5. 

It is possible to determine components in complex EPs where matrix effects can be severe. For example, zinc (as zinc borate), chlorine (as dechlorane flame retardant), antimony (as oxide) and fibre-glass have been determined in nylon using just one standard. Many users have refined the universal precalibrated programmes for standardless XRF and made them more efficient for matrix correction by using variable correction coefficients. OilQuant offers possibilities for analysing polymers [243]. Software packages usually provide ... 

Brominated and chlorinated organic flame-retardants can be analysed using either GC-MS or LC-MS. High resolution systems are required to identify the specific isomers. Quantification by bromine or chlorine content is normally achieved using XRF against standards in the same matrix. 

The surface area and degree of dispersion in the polymer matrix of the fire-retardant additive has a pronounced effect on its efficiency. Colloidal tin(IV) oxide is significantly more effective, in terms of its flame-retardant ability, than powdered tin(IV) oxide or B-stannic acid. 

Dispersive mixers are aiso used to reduce the size of soiid components in a moiten poiymer matrix. Soiid components inciude pigments, flame-retardant additives, and fiiiers. Many of these feedstock materiais are in the form of iooseiy bounded aggiomerates of smaiier primary particies. As the aggiomerate enters the shear stress fieid in the mixer, the aggiomerate wiii be decreased in size if the appiied shear stress is higher than the cohesive forces bonding the primary particies together. 

Campone L, Piccinelli AL, Ostman C, Rastrelli L (2010) Determination of organophosphorous flame retardants in fish tissues by matrix solid-phase dispersion and gas chromatography. Anal Bioanal Chem 397 799-806... 

Dumler R, Lenoir D, Tlroma H, et al. 1990. Thennal formation of polybrominated bi benzofurans and dioxins from decamromodiphenyl ether flame retardants influence of antimony-III oxide and the polymer matrix. Chemosphere 20( 10-12) 1867-1874. 

In order to rescue the amounts necessary to be added, PS-encapsulated Mg(OH)2 has been prepared. In a high speed mixer Mg(OH)2 was dispersed together with 3-(methacryloxy)propyltri-methoxysilane in acetone solution. After drying, the powder was encapsulated with PS by polymerizing styrene in the mixer. It is believed that the thus modified Mg(OH)2 can be more finely divided in the HIPS matrix an in this way better flame retardancy at lower levels of Mg(OH)2 is achieved (22). 

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