Fire, generally nanocomposites

Figures 19.19 through 19.21 present smoke, carbon monoxide, and carbon dioxide yield for all the PA6-based materials, respectively. Pure PA6 generally produces the lowest smoke and carbon monoxide, while PA6/NC and PA6/NC (UBE) yield slightly higher values. This is one of the main advantages of nanocomposites, as they do not result in increasing the production of smoke and toxic gases in comparison with most fire retardants. It is important to note that adding FR (both PA6/NP...

In general, when compared with the conventional polymer composites, polymer nanocomposites exhibit significant improvements in different properties at relatively much lower concentration of filler. The efficiency of various additives in polymer composites can be increased manyfold when dispersed in the nanoscale. This becomes more noteworthy when the additive is used to address any specific property of the final composite such as mechanical properties, conductivity, fire retardancy, thermal stability, etc. In case of polyolefin/LDH nanocomposites, similar improvements are also observed in many occasions. For example, the thermal properties of PE/LDH showed that even a small amount of LDH improves the thermal stability and onset decomposition temperature in comparison with the unfilled PE [22] its mechanical properties revealed increasing LDH concentration brought about steady increase in modulus and also a sharp decrease in the elongation at break [25]. While in this section, fire-retardant properties and electric properties of polyolefin/LDH nanocomposite were described in detail. 

Although there has been extensive research (e.g., [1-9]) on the fire retardation effects of nanoclay on neat polymers, relatively few studies [15-31] have been conducted with polymer blend systems. In Table 8.1, the polymer blends as well as the tests conducted in [ 15-31 ] are presented. From this table, it is clear that the majority of these studies have been devoted to the morphology and thermal stability of polymer blend nanocomposites very few studies actually focused on their fire performance. Nonetheless, these studies [15-31] have generally led to the conclusion that the addition of nanoclay to polymer blends can result in remarkable improvement in (a) mechanical properties, (b) compatibilization, (c) viscosity, (d) thermal stability, and (e) flammability. 

Polymer blending is useM in obtaining new materials with improved properties relative to their components, and polymer blends are widely used now in a large number of commercial applications. Polymer blends generally have poor fire properties, owing to the nature of polymers. To provide the required fire properties, traditional fire retardants, together with nanoclays, are used. In this chapter, we have summarized the main findings of previous studies on fire retardant polymer nanocomposites with polymer blends. The main conclusions are as follows ... 

Specific aspects of barrier formation were discussed above. A silicate or sihcate-char surface layer acting as a barrier for heat and mass transport is probably the main general fire retardancy mechanism of all layered-silicate nanocomposites. Most sources claim that this mechanism is responsible for the strongly improved performance in a cone calorimeter test. In particular, the strong reduction in PHRR is used to propose that layered silicates are the most promising approach for fire retardancy of polymers. However, the barrier effects and their influences on cone calorimeter results are not described in detail, so that the specific characteristics of these mechanisms are unclear. 

Nanoparticles added to thermoplastic polymers improve the mechanical properties, increase Tg and enhance fire retardancy. Nanoparticles in UPRs bring similar effects [217]. Montmorillonite (MMT) was used to obtain polymer nanocomposites [218]. That general approach was applied to the UPR-layered MMT nanocomposites. The structure of the nanocomposites was investigated by XRD and TEM. Organophilic MMT was applied dodecylammonium-bromide treated MMT was used. A UPR synthesized... 

To date much of the development of polymer nanocomposites has been for structural applications with current commercial applications such as the step assist for the Chevrolet Astro van introduced by General Motors in 2002. However, there are other composite functions, such as tribological resistance, low friction or fire retardancy which are important in other applications and with nanoscale reinforcements it is possible to mix several different types of reinforcement to generate improvements in a range of properties. The following sections discuss how such properties are improved in nanocomposites. 

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