Nanoparticles, flame retardants

The results obtained by Kuila et al. and Acharya et al. [63,64] from the EVA elastomer blended with lamellar-like Mg-Al layered double hydroxide (LDH) nanoparticles demonstrate that MH nanocrystals possess higher flame-retardant efficiency and mechanical reinforcing effect by comparison with common micrometer grade MH particles. Kar and Bhowmick [65] have developed MgO nanoparticles and have investigated their effect as cure activator for halogenated mbber. The results as shown in Table 4.2 are promising. 

PP-g-MA) silicate nanocomposites and intercalated thermoset silicate nanocomposites for flame-retardant applications were characterised by XRD and TEM [333], XRD, TEM and FTIR were also used in the study of ID CdS nanoparticle-poly(vinyl acetate) nanorod composites prepared by hydrothermal polymerisation and simultaneous sulfidation [334], The CdS nanoparticles were well dispersed in the polymer nanorods. The intercalation of polyaniline (PANI)-DDBSA (dodecylbenzene-sulfonate) into the galleries of organo-montmorillonite (MMT) was confirmed by XRD, and significantly large 4-spacing expansions (13.3-29.6A) were observed for the nanocomposites [335],... 

Lv, J., Qie, L., and Qu, B., Controlled synthesis of magnesium hydroxide nanoparticles with different morphological structures and related properties in flame retardant ethylene-vinyl acetate blends, Nanotechnology, 15, 1576-1581, 2004. 

Other Nanoparticles Associated with Various Flame Retardants.316... 

For more than a decade, numerous research studies have been carried out on the flame-retardant properties conferred by nanoparticles and mainly by organo-modified layered silicates (OMLS). Earlier work at Cornell University and National Institute of Standards and Technology in the United States showed that nanocomposites containing OMLS reduced polymer flammability and enhanced the formation of carbonaceous residue (char).14 Owing to a strong increase in polymer viscosity, impairing processability, and also due to the breakdown of ultimate mechanical properties, the acceptable rate of incorporation for nanoparticles to improve flame retardancy is generally restricted to less than 10 wt %. 

The different flame-retardant (FR) mechanisms of action of current nanoparticles, such as layered silicates, carbon nanotubes (CNTs), and nano-oxides or -hydroxides, according to their nature and interfacial modifications, are relatively well known and detailed in numerous works.5 13 These mechanisms are rather different from those exhibited by usual FRs and correspond mainly to the following physical, physicochemical, or chemical actions ... 

OTHER NANOPARTICLES ASSOCIATED WITH VARIOUS FLAME RETARDANTS... 

Combinations of Carbon Nanotubes with Flame Retardants and Nanoparticles... 

Z. Wang, E. Han, and W. Ke, Effect of nanoparticles on the improvement in fire-resistant and anti-ageing properties of flame-retardant coating, Surf. Coat. Technol., 2006, 200 5706-5716. 

It is intended to use these properties for the assessment of alternative flame retardants (FRs) (including nanoparticles, phosphates, and inorganic metal oxides) in comparison with brominated fire retardants by quantitatively assessing ... 

Polyamides It is very difficult to incorporate additives in polyamides because of their melt reactivities. The recent developments for the flame retardancy of polyamides concern mainly the inclusion of nanoparticles, discussed in Section 24.5.3. 

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. 

Zammarano, M. Gilman, J.W. Kramer, R.H. et al. Effect of nanoparticles on flammability of flexible polyurethane foams. Proceedings of 19th Annual BCC Conference on Flame Retardancy—Recent Advances in Flame Retardancy of Polymeric Materials, Stamford, CT, 2008. 

Both intercalated and exfoliated nanocomposites, containing 3-5% of nanoparticles (w/w), reportedly show better or comparable flame resistance compared with plastics filled up to 30-50% with traditional flame retardants. Another way to increase flame retardancy is to combine ATH or magnesium hydroxide with organo-clays. It was reported that organoclays and some classical flame retardants, such as brominated compounds, showed a synergism between them [13]. 

Generally, nanomaterials as flame retardants do not have commercial applications. Data obtained are commonly recognized as preliminary, and they are described here just as preliminary as well. One more example of such data is a study of heat release and char formation (in per cent units) at burning of polypropylene filled with magnesium hydroxide (5 pm, 1 pm particles, and nanoparticles) (Table 14.9). 

Nanofillers and nanocomposites, 154, 476 Nano-particles as flame retardants, 476 Nanoparticles, 79, 126, 154, 155... 

For PNCs, the layered double hydroxides (LDHs) constitute a new class of mainly synthetic, reinforcing nanoparticles. During synthesis, LDHs may be preintercalated with organic anions. Unfortunately, most LDH platelets are thin, f=0.6 0.1nm, small in diameter, d=30 to 40 nm [Wu et al., 2007]), and decompose thermally at T IOTC [Camino et al., 2001]) consequently, their main application has been for absorption of HCl during dehydrochlorination of poly(vinyl chloride) (PVC) and halogenated polymers, or as flame retardants. The flow behavior of polyethylene (PE) with LDHs was reported to be similar to that of CPNCs [Costa et al., 2006]. There are no commercial PNCs with LDHs on the market, but experimental products such as Perkalite, a preintercalated aluminum-magnesium (Al-Mg) LDH, have been... 

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