Barrier for Heat and Mass Transport

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. 

FIGURE 5.5 Heat release rate monitored in cone calorimeter experiments (irradiance = 50 kW/m ) (a) PP-g-MA, PP-g-MA measured with the modified sample holder and PP-g-MA/5 wt% E (b) Epoxy, Epoxy measured with the modified sample holder, and 

SPECIFIC IMPACTS OF THE PRINCIPAL FIRE RETARDANCY MECHANISMS 

TABLE 5.1 Comparison of the Typical Reduction in PHRR for Nanocomposites with the Ratio of Averaged (Steady-State) HRR/PHRR Using 35 kW/m Irradiation 

Nanocomposite Reduction of PHRR for Well-Prepared Nanocomposites (%) Ratio Between Averaged (Steady-State) HRR and PHRR (%) 

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