Dielectric properties of polymonochlorotrifluoroethylene

Abstract

The dielectric properties of three kinds of polymonochlorotrifluoroethylene having various degrees of crystallinity were studied. The measuring instruments by which the dielectric properties can be measured over a wide range of frequency are briefly described. The dielectric measurements for three samples are made over a frequency range 0.1 to 106 cycles/sec. and a temperature range of −50 to 140°C. The main conclusions from the experimental results are as follows. Two dielectric dispersions observed would be due to the polar groups in amorphous regions. At the melting temperature, the positions of the two dispersions would coincide with each other. The energies of activation for the two loss processes are 16.8 and 57.0 kcal., respectively. Interpreting from the variation of the magnitude of the dielectric dispersion with temperature, the glass transition temperature of this polymer extends over the wide range from −80 to 60°C. For the low temperature dispersion, the value of Cole‐Cole's parameter β has constant value of 0.3 below 20°C. and increases with temperature above 20°C.

Mechanical properties of a model of attractive colloidal solutions

“…The non-ergodicity factors are certainly different, but it is of interest to consider Figure 6 where we learn that these difference in non-ergodicity factor alone is sufficient to cause the considerable softening of the glass as the volume fraction exceeds its critical value of φ ≃ 0.48. Figure 5: Plots of the coordination number n c (19) and of the mean bonding number n b (18) as a function of the volume fraction φ, along the liquidattractive glass transition line B 2 . The two behaviours are nearly linear, except for small deviations, at low volume fraction for n b .…”

“…Given that such observations appear to be associated with quite strong short-ranged attractions driven by depletion forces, or grafted chains onto larger particles, it would seem likely that indeed such systems are examples of those we currently discuss. On the other hand, as yet, there appear to be no clear reports of colloidal glass-glass transition in the experimental literature, but the typical logarithmic decay of density correlations, that MCT predicts to happen close to an A 3 singularity [17] has been observed in the past, for the glass transition of some polymeric systems [18,19]. More recently a logarithmic decay has been reported in a micellar system with short-ranged attractive interactions, and this may be related to a proximate glass-glass transitions as these authors point out [20].…”

An ultra low frequency bridge for dielectric measurements

“…In view of these facts, in practice th e bridge is operated with Og shorted . The impedances 6 in terms of parallel compon ents, The variable factors in equaLion s (6) and 7becom e arc given by 1 1 .…”

“…ubstituting these valu es in to eq (2) one obtains the following, upon separation of r eal and imaginary parts and Since the subs LiLu tion method is employed , equations (6) and 7 • With the unkno wn " out" we denote t h e value of RI and Os at balance as R ; ftnd 0 ; respectively.…”

“…N akajima and Kondo [5] circumvent the impedances-to-ground problem by operating the generator in a two terminal manner. Their bridge (briefly described elsewhere by Nakajima and Saito [6]) utilizes a vVagner earthing devi ce, a condu ctan ce shifter , and an ungrounded or "floating" detector. Dielectric measurements with this apparatus are carried out bv the direct method.…”