Abstract
Summary: The thermodynamic properties โ the temperature dependence of heat capacity and the temperatures and enthalpies of physical transitions โ of poly(pentamethylene urethane) and poly(hexamethylene urethane) have been studied over the range 6 to 450 K by precision adiabatic vacuum and dynamic calorimetry. Their energies of combustion, ฮ~c~U, have been measured in a calorimeter with a static bomb and an isothermal shield. The calorimetric data were used to determine the temperature dependences of the heat capacity $C_{\rm p}^{\rm 0}$โ=โf(T) for poly(pentamethylene urethane) and poly(hexamethylene urethane) in crystalline and amorphous states, to calculate the thermodynamic parameters of the glass transition and the glassy state, the thermodynamic quantities of fusion and the thermodynamic functions $C_{\rm p}^{\rm 0}$(T), H^0^(T)โโโH^0^(0), S^0^(T)โโโS^0^(0) and G^0^(T)โโโH^0^(0) of the polymers for the temperature range from 0 to 450 K. The enthalpy of combustion ฮ~c~H^0^ and the standard thermodynamic characteristics of formation, namely, the enthalpy, ฮ~f~H^0^, entropy, ฮ~f~S^0^ and Gibbs function, ฮ~f~G^0^, of the substances under discussion were estimated at Tโ=โ298.15 K. The regions of thermal resistance for the tested compounds were determined calorimetrically.
Temperature dependence of $C_p^0$ of poly(pentamethylene urethane)(A) and poly(hexamethylene urethane)(Aโฒ).
imageTemperature dependence of $C_p^0$ of poly(pentamethylene urethane)(A) and poly(hexamethylene urethane)(Aโฒ).