Thermal conductivity and specific heat of an epoxy resin/epoxy resin composite material at low temperatures

Abstract

The thermal conductivity and the specific heat of pure and filled epoxy resins are measured in the temperature range between 2 and 80 K. In order to study the low‐temperature thermal conductivity of the filled samples without any acoustic mismatch a filler completely identical with the matrix material is used. The characteristic plateau of the thermal conductivity of amorphous solids between 5 and 15 K is extented to elevated temperatures with growing filler content. A second plateau of the thermal conductivity between 30 and 50 K is observed. It is suggested that the second plateau arises from a mechanism which is due to the anisotropic bending forces in polymers and related materials.

Some Peculiarities in Thermal and Relaxation Properties of Polymers and Related Materials at Low Temperatures

“…O n the other hand, we have found only few thermal conductivity and specific heat measurements of polymers concerning the temperature range between 20 and 80 K in detail. As shown in an earlier work [3], the thermal conductivity and the specific heat of several polymers are not smooth functions within this temperature range. In the present paper, this problem shall be discussed in a more detailed manner and in the light of the work of other authors.…”

“…1 shows the thermal conductivity values for some selected materials plotted against temperature. All of these materials, amorphous and semicrystalline, have been found to exhibit a shoulder in the thermal conductivity plot near 50 K which shall be called the second plateau since it was observed in addition to the characteristic plateau of the thermal conductivity of amorphous solids between 5 and 15 K. It has been suggestes [3] that the second plateau arises from an inhibition of the intrachain heat conduction by chain defects and, therefore, the second plateau occurs in a temperature range where thermal transport inside the chain molecules becomes important. In the same temperature range, the specific heat of some materials exhibits a hump.…”

“…We suggest that both the cryogenic relaxation process and the anomaly of the thermal properties near 50 K [3] are independent of the detailed chemical composition of the material and arise from the anisotropy of bonding forces in polymers and related materials. Therefore measurements of inorganic glasses are included in the discussion.…”

“…The thermal conductivity and specific heat measurements have been described elsewhere [3,5,61. In brief, a usual steady state technique was applied to determine the thermal conductivity.…”

Tunneling Systems in Amorphous and Crystalline Solids

“…Since the thermal activation gives an additional contribution to the heat absorption at To ~ 1.63 K, the absolute value of the heat absorption is larger than the corresponding heat release. Sahling (1989) d Nittke et al (1995) e Stephens (1973) f Scheibner and Jackel (1985) g Schwark et al (1985) h Zimmermann and Weber (1981a) i Zimmermann (1984) i Kolac et al (1987) 2.5.4 Correlation Between the Heat Release and Other Low-Temperature Properties 76 at To = 1.3K to rO.…”