Thermodynamics of interpenetrating polymer networks based on crosslinked poly(cyanurate) and poly(urethane) in the range from T → 0 to 340 K

The temperature dependences of heat capacity of interpenetrating polymer networks based on crosslinked poly(cyanurate) and poly(urethane) derived from glycerol, 2,4-tolylene diisocyanate, and oligo(oxytetramethylene glycol) (M n = 10 3 ) in the 6-340 K range were studied using adiabatic vacuum calorimetry with a precision of about 0.2%. Using a calorimeter equipped with a static bomb and an isothermal shell, the enthalpies of combustion of the crosslinked PU and of the three samples of interpenetrating polymer networks containing 10, 30, and 50 wt % of the crosslinked poly(cyanurate) were measured. On the basis of the experimental data, the thermodynamic functions of the research subjects H°(T)-H°(0), S°(T)-S°(0), and G°(T)H°(0) for the range from T → 0 to T= 340 K were calculated and the standard enthalpies of combustion ΔH c ° and the thermodynamic parameters of formation ΔH° f , ΔS° f , and ΔG° f at 298.15 K were determined. The data obtained were used to calculate the enthalpy ΔH° p , entropy ΔS° p , and Gibbs functions ΔG° p for the preparation of interpenetrating polymer networks through the reaction of crosslinked poly(cyanurate) and bisphenol A dicyanate ester (with a content of poly(cyanurate) in the networks of 10, 30, 50 wt %) in the range from T → 0 to T = 340 K. It was shown that the isotherms of diverse thermodynamic properties of interpenetrating polymer networks plotted versus their composition, in particular, the molar fraction of the crosslinked PU per conditional mole, can be described by straight lines. This makes it possible to estimate the thermodynamic behavior of interpenetrating polymer networks of any composition at standard pressure within a wide temperature range.