Flame retardation by polymer-clay nanocomposites

The comprehensive flame retardation of polymer-clay nanocomposite materials was reported by Dr. Jeff Gilman and others at NIST [7]. They disclosed that both delaminated and intercalated nanoclays improve the flammability properties of polymer-layered silicate (clay) nanocomposites. In the study of the flame retardant effect of the nanodispersed clays, XRD and TEM analysis identified a nanoreinforced protective silicate/carbon-like high-performance char from the combustion residue that provided a physical mechanism of flammability control. The report also disclosed that The nanocomposite structure of the char appears to enhance the performance of the char layer. This char may act as an insulation and mass transport barrier showing the escape of the volatile products generated as the polymer decomposes. Cone calorimetry was used to study the flame retardation. The HRRs (heat release rates) of thermoplastic and thermoset polymer-layered silicate nanocomposites are reduced by 40% to 60% in delaminated or intercalated nanocomposites containing a silicate mass fraction of only 2% to 6%. On the basis of their expertise and experience in plastic flammability, they concluded that polymer-clay nanocomposites are very promising new flame-retarding polymers. In addition, they predict that the addition 

Intmduction to flame retardancy of polymer-clay nanocomposites 

Recently Jho et al. [25] pointed out that modified montmorillonites alone are not sufficient as flame retardants in cable applications. Also, Wilkie [26] gave a clear statement It 

Charring polymers such as PA-6 and PA-6 nanocomposites were used by Bourbigot et al. [27] to improve the flame retardancy of EVA. The organoclay increased the efficiency of the char as a protective barrier by thermal stabilization of a phosphorcarbonaceous structure in the inmmescent char and additionally the formation of a ceramic layer. Hu et al. [28] used a blend of PA-6 and EVA nanocomposite to improve the flame retardancy of PR 

With greatly reduced burning rate, heat release, and char formation, it is possible to combine nanofiller with traditional flame retardants to achieve satisfactory regulatory approvals such as various UL ratings. In fact, several studies have revealed synergistic effects of combinations of nanofillers with traditional microsized flame retardants. 

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