Thermal conductivity polymer composites

As a good first approximation (187), the heat conduction of low density foams through the soHd and gas phases can be expressed as the product of the thermal conductivity of each phase times its volume fraction. Most rigid polymers have thermal conductivities of 0.07-0.28 W/(m-K) and the corresponding conduction through the soHd phase of a 32 kg/m (2 lbs/fT) foam (3 vol %) ranges 0.003-0.009 W/(m-K). In most cellular polymers this value is deterrnined primarily by the density of the foam and the polymer-phase composition. Smaller variations can result from changes in cell stmcture. 

There are a lot of correlations, proposed in the literature, allowing one to calculate the composition thermal conductivity coefficient A,(thermoplastic polymer compositions containing four types of fiUer. The volume concentration varied within the interval of 0.1 to 0.4 volume shares of the filler, the value of ratio varied from 3 through to 354. Resulting from the comparison of the results of calculations by different equations with experimental data, it was found that the following expression is the best possible [72] ... 

Reinforced polymers and thermally conductive polymer composites. Polymers are often reinforced with fillers to... 

Figure 7.8 presents measurements of the heat dissipation for selected materials with different thermal and mechanical properties presented as a ratio of the thermal conductivities of the surface to the probe. From the simple Eq. (7.2) for the composite thermal conductivity coefficient, we can conclude that the method should be more sensitive for materials such as polymers with thermal conductivity less than the conductivity of the tip material than it is for materials with higher thermal conductivity (small variation in AQ) (Fig. 7.8). 

Both the CB and SG provided an improvement in the TC compared to the pure polymer. The SG caused the most significant increase in both inplane and through-plane composite thermal conductivity. 

The thermal conductivity of a cellular polymer can change upon aging under ambient conditions if the gas composition is influenced by such aging. Such a case is evidenced when oxygen or nitrogen diffuses into polyurethane foams that initially have only a fluorocarbon blowing agent in the cells (32,130,143,190,191,198-201). 

Applied Sciences, Inc. has, in the past few years, used the fixed catalyst fiber to fabricate and analyze VGCF-reinforced composites which could be candidate materials for thermal management substrates in high density, high power electronic devices and space power system radiator fins and high performance applications such as plasma facing components in experimental nuclear fusion reactors. These composites include carbon/carbon (CC) composites, polymer matrix composites, and metal matrix composites (MMC). Measurements have been made of thermal conductivity, coefficient of thermal expansion (CTE), tensile strength, and tensile modulus. Representative results are described below. 

All VGCF was graphitized prior to composite consolidation. Composites were molded in steel molds lined with fiberglass reinforced, non-porous Teflon release sheets. The finished composite panels were trimmed of resin flash and weighed to determine the fiber fraction. Thermal conductivity and thermal expansion measurements of the various polymer matrix composites are given in Table 6. Table 7 gives results from mechanical property measurements. 

Though short fiber-reinforced mbber composites find application in hose, belt, tires, and automotives [57,98,133,164] recent attention has been focused on the suitability of such composites in high-performance applications. One of the most important recent applications of short fiber-mbber composite is as thermal insulators where the material will protect the metallic casing by undergoing a process called ablation, which is described in a broad sense as the sacrificial removal of material to protect stmcrnres subjected to high rates of heat transfer [190]. Fiber-reinforced polymer composites are potential ablative materials because of their high specific heat, low thermal conductivity, and ability of the fiber to retain the char formed during ablation [191-194]. 

Bigg, D. M. Thermal Conductivity of Heterophase Polymer Compositions. Vol. 119, pp. 1-30. 

The mechanisms and reasons of catalytic activity of polyaniline (PANI)-type conducting polymers toward oxygen reduction in acidic and saline solutions are investigated by electrochemical and quantum-chemical methods. The PANI/thermally expanded graphite compositions were developed for realization of fully functional air gas-diffusion electrodes. Principally new concept for creation of rechargeable metal-air batteries with such type of catalysts is proposed. The mockups of primary and rechargeable metal-air batteries with new type of polymer composite catalysts were developed and tested. 

CNTs can enhance the thermal properties of CNT-polymer nanocomposites. The reinforcing function is closely associated with the amount and alignment of CNTs in the composites. Well-dispersed and long-term stable carbon nanotubes/ polymer composites own higher modulus and better thermal property as well as better electronic conductivity (Valter et al., 2002 Biercuk et al., 2002). Both SWNT and MWNT can improve the thermal stability and thermal conductivity of polymer, the polymer-CNT composites can be used for fabricating resistant-heat materials. 

Du FM, Guthy C, Kashiwagi T, Fischer JE, Winey Kl. An infiltration method for preparing singlewall nanotube/epoxy composites with improved thermal conductivity. Journal of Polymer Science PartB Polymer Physics. 2006 May 15 44(10) 1513-9. 

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