Thermal conductivity polymer flammability

It is known that increased char yield is usually associated with improved flammability behavior ( 1). This can be understood if one considers that the volatile flammable products can only diffuse with difficulty through the char, and that the thermal conductivity of a porous char layer is relatively poor (2). The structure of the polymer can contribute to the amount of char formed based on the character of the functional groups present and the nature of the backbone (2,3). Ritchie ( ) found that for a series of unsaturated polyesters and their copolymers, the temperatures at which carbon dioxide is eliminated was in the range of 280 to 345°C depending on the structure of the polyester. Aliphatic polyesters and their copolymers have less thermal... 

Polymer clay nanocomposites are already used in many applications to enhance existing properties of a particular material, and development should be focused on the true multifunctional materials. Certainly, clay nanocomposites will continue to be used for enhanced mechanical, flammability, and gas barrier properties, but fundamental limits in clay chemistry prevent them from being used easily in applications requiring electrical/ thermal conductivity or optical properties. Similarly, combinations of... 

Polymer System Glass Content, wt% Property Deflection 66 psi Temp., °F 264 psi Coef. of Thermal Expansion, ( yin-5° Coef. of Thermal Conductivity, Btu Maximum UL Temp Flammability Deformation Under Load 2000 psi, 24 h, 50° C, %... 

FLAMMABILITY Table 4. Polymer Thermal Conductivity, Density, Heat Capacity, and Thermai Diffusivity at Room Temperature ... 

Fillers can modify the properties of the cured polymer in a wide variety of ways. Some examples of properties readily modified by incorporation of fillers are mechanical properties such as stiffness, hardness, strength and toughness, and thermal properties such as expansion, conductivity or thermal decomposition. The latter can have a considerable effect on flammability and smoke generation. Fillers are also an important way of varying and enhancing aesthetics. 

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. 

A trend that has already begun to arise is the use of multiple types of nanofillers in the same polymer to yield a multicomponent nanocomposite. Some workers have found that some types of nanofillers cannot bring all of the desired properties to the final material, so clays have been combined with multiwall carbon nanotubes to bring enhanced properties.The observation for most polymer additives is that they cannot be used for all applications in all polymers, and the same observation will surely be made about nanocomposites. A clay may be used to enhance the flammability performance, bnt it could also be combined with a conductive nanoflller to impart antistatic aspects or electrical conductivity in the final system. One potential way to look at the use of multiple nanoparticles is that each nanoparticle plays a complementary role in flammability reduction. For example, one could choose a clay for mass loss rate or fuel release reduction, but then use a colloidal particle to flu in the gaps between clay plates as the nanocomposite thermally decomposes. Perhaps even more useful, the colloidal particle could have catalytic or flame retardant properties that encourage... 

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