B. Lebedev, T. G. Kulagina, V. S. Svistunov
1984
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0
Influential Citations
4
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Journal
Polymer Science U.s.s.r.
Abstract
An adiabatic vacuum calorimeter has been used to study the thermal capacity Cp° of 1,1,3,3,5,5-hexaethylcyclotrisiloxane and polydiethylsiloxane in the region 13–330 K with an error of 0·2% with determination of the temperatures and enthalpies of the physical transitions. It was found that the first exists in three crystalline and liquid states and the second in the partially crystalline and liquid states, the polymer crystals existing in two modifications. The functions H0(T)−H0(0), S°(T) and G°(T)−H°(0) of the monomer and polymer have been calculated. The zero entropy Sg°(0) of glassy polydiethylsiloxane and the difference in the zero enthalpies of the polymer in the glassy and crystalline states Hg°(0)−Hc°(0) have been evaluated. The calorimeter was used to measure the enthalpy of polymerization of hexaethylcyclotrisiloxane in bulk at 433 K and p = 101·325 kPa. From the results the authors calculate the values ΔHp° ΔSp° and ΔGp° of the process hexaethylcyclotrisiloxane→polydiethylsiloxane for the region 0–330 K. The upper limiting temperature of polymerization of hexaethylcyclotrisiloxane has been evaluated.