Page 382 - Handbook of Adhesives and Sealants

338 Chapter Nine

tivity drops drastically when mixed with organic resins. Aluminum
oxide is commonly used. Table 9.6 lists thermal conductivity values
for several metals as well as for beryllium oxide, aluminum oxide, and
for several filled and unfilled resins. Figure 9.7 shows the thermal
conductivity values for an epoxy resin as a function of volume fraction
of several heat conductive fillers.

9.4 Commercial Formulations
There are literally hundreds of thousands of commercial adhesive
products of various types available to all market sectors. Some of these
commercial adhesive products are described in the next chapter. Ad-
hesive products are made available from many thousands of adhesive
suppliers that range from very small business organizations of several

TABLE 9.6 Thermal Conductivity of Metals, Oxides, and Conductive
Adhesives 20
Thermal conductivity at 25 C
2
(Btu/hr Fft /ft)
Silver 240
Copper 220
Beryllium oxide 130
Aluminum 110
Steel 40
Eutectic solders 20–30
Aluminum oxide 20
Best silver-filled epoxy adhesives 1 to 4
Aluminum-filled (50%) epoxy 1 to 2
0.8 to 1
Epoxy filled with 75% by wt. Al 2 O 3
0.3 to 0.4
Epoxy filled with 50% by wt. Al 2 O 3
0.2 to 0.3
Epoxy filled with 25% by wt. Al 2 O 3
Unfilled epoxies 0.1 to 0.15
Foamed plastics 0.01 to 0.03
Air 0.015
Table for Conversion of Thermal Conductivity Units
2
2
2
2
g cal/cm sec C/cm w/cm C/cm Btu/ft hr F/ft Btu/ft hr F/in
1.0 4.19 242 2900
0.23 1.0 58 690
4.13 10 3 0.0173 1.0 12.0
3.44 10 4 1.44 10 3 0.083 1.0
Heat transfer k thermal conductivity
formula: T temperature drop
k T cross material
q
x q heat flow/unit area
x material thickness