Thermodynamics of linear polyurethanes on basis of 1,4-diisocyanatobutane with 1,4-butanediol and 1,6-hexanediol in the range from T → 0 to 490 K

The temperature dependence of heat capacity and characteristics of physical transformations of partially crystalline linear aliphatic polyurethanes based on 1,4-diisocyanatobutane with 1,4-butanediol and 1,6-hexanediol have been studied over the range 6.5–490 K by precision adiabatic vacuum and dynamic calorimetry. The calorimetric data were used to determine the thermodynamic quantities of devitrification and fusion and to calculate the standard thermodynamic functions Cp0(T), H0(T) − H0(0), S0(T) and G0(T) − H0(0) of linear polyurethanes in totally crystalline and amorphous states. The values of the fractal dimension D in the function of multifractal generalization of Debye's theory of the heat capacity of solids were estimated and the character of heterodynamics of their structures was detected. The energies of combustion of the substances were measured in a calorimeter with an isothermal shield and a static bomb. The enthalpies of combustion and the standard thermodynamic characteristics of formation of the polymers at T = 298.15 K were calculated too. The standard thermodynamic characteristics of polycondensation processes in bulk of 1,4-diisocyanatobutane with 1,4-butanediol and 1,6-hexanediol followed by the formation of linear polyurethanes were determined in the range from 0 to 350 K. A comparative analysis of the corresponding standard thermodynamic properties of the polymers under consideration and polyurethanes of isomeric structure was made and some dependences of their change on various conditions were found.