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The specific heat cp of amorphous polycarbonate and amorphous polystyrene has been measured at pressures up to p = 0.7 GPa in the temperature range 0.2K

We measured the dielectric response, e ′( ω )+i e ″( ω ), of polycarbonate (PC) at various frequencies (1–200 kHz) in the temperature range between 40 mK and 300 K. Under the application of hydrostatic pressure (up to 0.6 GPa) the low temperature properties due to two level tunnelling systems could be examined as well as thermally activated processes in the high temperature regime.

When predicting and altering the properties of composites, one has to consider not only the peculiarities of the components themselves but also the boundary layer between the filler and the polymer matrix. The aim of this paper is to study the influence of the boundary layer on the low temperature thermal conductivity and specific heat of an epoxy resin/particle composite. Measurements of the glass transition temperature and the hardness are interpreted, as obtained from the filler surface, and electron micrographs of the boundary layer are presented.

The thermal conductivity at low temperatures (between 0.5 K and 100 K) was measured for diolmodified epoxies. Diglycidyl ether of bisphenol A (DGEBA) was modified for this purpose by aliphatic diols with the structure HO-(-CH2-)n-OH in the presence of catalyst (either N,N-dimethyl benzylamine or magnesium perchlorate). Sample series with diols of n=4,8 and 12 were synthesized and measured. The results at T

The thermal conductivity of modified epoxy resins was investigated from 0.5 to 80 K. Two series of samples with different cross-link densities were used. The results are discussed.

The thermal conductivity λ, the specific heat c, the thermal expansion α, the acoustic and dielectric properties of polycarbonate (PC), of polystyrene (PS) and of an epoxy resin were measured in the temperature ranges between 0.1 K and 80 K (λ c) and between 4 K and 300 K (α). The measurements show the typical low-temperature behavior of amorphous solids. Below 20 K the results can be explained in the framework of the soft potential model. Above 20 K with increasing temperature λ, and α show between 30 K and 50 K a distinct decrease in slope of the temperature dependence. The sound velocity shows for PC and PS the typical decrease with increasing temperature. For PC the maximum in the dielectric losses shifts with increasing frequency and at increasing pressure to higher temperature.

Measurements of thermal conductivity, specific heat, and dielectric properties of an epoxy resin after electron, gamma, fast-neutron, and thermal-neutron irradiation are presented. The experimental results show the influence of the different types of radiation on the typical amorphous behaviour of the thermal properties. The H2-permeation rate for two types of carbon-fibre-reinforced plastics are presented.

We have measured the dielectric response e(ω) and the thermal conductivity κ of polystyrene (PS) and of polycarbonate (PC) under high hydrostatic pressure (0.1 MPa MPa ) and at low temperatures ( 50 mK K ). The investigations show a pressure influence on the minimum temperature of Δe′/e′ and on κ. With the pressure dependence of the density and sound velocity of PC and PS the influence of pressure on the tunnelling constant Ci can be determined. These results show that the product P γ l,t 2 of the standard tunnelling model (STM) scales with the pressure-dependent elastic constants c11 and c44.

We measured the thermal conductivity λ of Polycarbonat (PC) in the temperature range from 3 K to 150 K under application of hydrostatic pressure up to 1.3 GPa. A strong influence of pressure on λ was observed over the entire temperature range. An additional measurement of the pressure dependence of density showed that the density of PC increases appreciably with pressure. The thermal conductivity data were thus corrected considering the changes of density. The corrected data show an increase of λ with pressure only in the plateau region of thermal conductivity. Similar results were measured for vitreous silica [1] and epoxy resin [2], where the data of vitreous silica show an opposite behaviour of λ with increasing pressure.

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.

The thermal condcutivity and specific heat of amorphous, non-oriented polycarbonate were measured in the temperature range between 2 and 80 K. The temperature dependence of the thermal conductivity below 20 K indicates the presence of heterogeneities. The specific surface of these heterogeneities is estimated from the phonon mean free path length. The heterogeneous structure is preserved when the material is heated above the glass transition temperature. Die Warmeleitfahigkeit und die spezifische Warmekapazitat von amorphem, nichtorientiertenl Polycarbonat wurden bei Temperaturen zwiscken 2 und 80 K gemessen. Die Temperaturabhangigkeit der Warmeleitfahigkeit unterhalb von 20 K zeigt das Vorhandensein von Heterogenitaten an, deren spezifische Oberflache aus der mittleren freien Weglange der Phononen abgeschatzt wird. Die heterogene Struktur bleibt nach Erwarmen des Materials aber die Glasabergangstemperatur erhalten.

Measurements of the thermal conductivity and of the dielectric properties of an electronirradiated epoxy-resin are presented. The experimental results for varying radiation doses of structural investigations of electron-irradiated epoxy-resin 1 are discussed.

Measurements of the thermal conductivity and of the dielectric properties of an epoxy-resin irradiated by fast and thermal neutrons are presented. The discussion of the experimental results accounts for the radiation dose and energy of neutrons.

The thermal conductivity λ of polycarbonate (PC) has been measured in the temperature range 3–150 K under hydrostatic pressure up to 1.3 GPa [Geilenkeuser, R., Weise, F. and Jackel, M., Czech. J. Physics , 1996, 46, 2251 ( Proc. LT 21 , Prag, August 1996)]. A strong influence of pressure on λ has been observed over the entire temperature range. Additional measurements of the pressure dependence of the density showed that the density of PC, polystyrene (PS), epoxy resin and PTFE (Teflon) increased considerably with pressure (Jackel, M., Weise, F. and Geilenkeuser, R. In Proc. ICEC16/ICMC , Kitakyushu, May 1996, in press). At a pressure of 1.3 GPa the relative increase of the density amounts to 25%. The thermal conductivity data were corrected for the changes of density, sample geometry and sound velocity. The corrected data show an increase of λ with pressure only in the plateau region of thermal conductivity. Similar results were measured for vitreous silica (Jackel, M., Wagner, K. and Hegenbarth, E., Physica B , 1996, 219&220, 308) and epoxy resin (Grace, J.M. and Anderson, A.C., Phys. Rev. B , 1989, 40, 1901).