The thermal conductivity of polyolefins and halogen-substituted polymers was studied in a broad temperature interval spanning both solid and melt states, in the range of pressures from 0.1 up to 100 MPa with the aid of a high-pressureλ-calorimeter in the continuous heating regime. Treatment of data on the pressure dependence of the thermal conductivity of melts in terms of Barker's equation yielded the values of ‘quasilattice’ Grueneisen parameter γB which exhibited the same dependence on molecular structure of a polymer as the parameter 3C/p from the Simha-Somcynsky equation of state (number of external degress of freedom per chain repeat unit). Analysis of the dependence of the thermal conductivity of polyethylene on the degree of crystallinity revealed the inadequacy of the current two-phase model which does not account for the microheterogeneity of the ‘amorphous phase’. It was concluded that interchain heat transfer makes the dominant contribution to the thermal conductivity of polymers both in amorphous and in crystalline states.
Aqueous solutions containing poly(vinyl-pyrrolidone) and sodium caprylate, or poly(vinyl-pyrrolidone) and tetraethylammonium
perfluorooctanesulfonate,respectively, have been investigated by volumetric, ionic conductivity and surface tension methods.
The presence of an interaction region has been determined from conductivity and surface tension. The width of such a region
depends on the amount of polymer in the mixture,temperature, surfactant content and added electrolyte (NaCl). The observed
behaviour was explained in terms of the combined effects played by the alkyl-chain hydophobicity, polar head group(s) and
An approximate solution to a mass action model for the binding of surfactants onto polymers has been introduced. It allows
determining the width of the interaction region as a function of polymer mass percent in the mixture.
Authors:B. Fillon, A. Thierry, B. Lotz, and J. Wittmann
Nucleation of crystallizable polymers is quantified through an efficiency scale obtained and calculated using differential
scanning calorimetry (DSC). This scale, defined in self-nucleation experiments, is a simple, convenient and reliable calorimetric
efficiency scale. Typical nucleating agents for isotactic polypropylene are evaluated; they rate at best at 60 to=70% on this
Authors:J. Zieliński, A. Bukowski, and B. Osowiecka
Results of studies dealing with an effect of polymers (selected kinds) and plasticizer on thermal stability of coal-tar pitch
Factors being decisive in miscibility of composition constituents and instability of bitumen-polymer-plasyticizer mixtures
Authors:O. B. Salamatina, S. N. Rudnev, V. V. Voenniy, and E. F. Oleynik
Measurements of the mechanical work (A), the heat of deformation (Q) and differences between these quantities, i.e. the internal energy (ΔU) stored in samples were performed under the unidirectional compression loading conditions by using constant temperature deformation calorimetry. It is shown for several glassy (PS, PC, PI-BD, PET, epoxy-amine network, ABS) semi crystalline (PBT, PET) polymers and blends (PC: ABS, PC: PBT), that 45–85% of the mechanical work of deformation is converted to internal energy stored in deformed samples ΔU is quite high as compared with metals.
It is evidenced that due to the kinetic character of the glass transition as a ‘freeze in’ process, PVT measurements extended over the glass transition range depend not only on the thermal history but also on the pressure acting during the formation of the polymeric glasses. As a consequence metastable glasses are formed which show during heating of the glassy polymer through the glass transition range ‘volume relaxation zones’, characterized by a retarded increase or even decrease of the volume. The width of the ‘relaxation zone’ increases with increasing pressure and depends additional on the mode of operation used during the PVT measurements. In the same time a pressure induced shift of the glass temperature to higher temperatures is observed, the shift being the greater the stiffer the polymer, i.e. the higher the glass temperature of the polymer at atmospheric pressure. Due to the metastable character of polymeric glasses the evaluation of universal equations of states is thus not ingenious for polymeric glasses, because the deduced EOS will be valid only for that given glass characterized by a well defined thermal and pressure history. Additionally the EOS is influenced by the unknown time dependent aging and relaxation processes within polymeric glasses.
Evidence of the existence of a high-limit degradation temperature for polymers is reported. At this high-limit temperature,
the rate of polymer thermolysis exceeds the reaction rate predicted by the Arrhenius law by many orders of magnitude. An explanation
is proposed for the observed behaviour, based on the disappearance of intermolecular interactions. For the study of degradation
reactions under high-limit temperature conditions, new methods of fast (pulsed) thermal analysis are presented. The investigated
samples, as very thin films, are brought into tight contact with a hot moving metal surface. Under these conditions, the heating
rate exceeds 104 deg/s, allowing estimation of accompanying decomposition rates for heating times of the order of 0.01 s.
It has been shown that simultaneous measurements of reflected light intensity (RLI) with DSC can give additional and valuable
information for the thermal analysis of materials including pure organic and inorganic chemicals, natural and synthetic polymers
This paper extends the range of polymers studied and examines the possibility of improving the reproducibility and quantitative
nature of RLI measurements. Polymer crystallisation, the curing of epoxy resins, the action of fire retardant additives and
the degradation of polymers and proteins are among the systems studied.
The technique of temperature waves to measure the complex thermophysical characteristics of materials has been proposed. The relations for the moduli and arguments of these characteristics for the case of plane temperature waves have been calculated. The temperature dependences of the moduli and arguments of complex thermophysical characteristics of polyvinylacetate (PVAc) at different frequencies and also the temperature dependences of its vibrational and configurational heat capacities have been determined. It has been shown that the vibrational heat capacity of PVAc in the region of softening grows sharply and its configurational heat capacity goes through a peak. The segmental mobility has been found to affect the heat transfer in the polymer in an ambivalent way causing both a decrease and increase of thermal conductivity.