Enthalpies of vaporization of oligomers of poly(hexamethylene sebacate) and esters of alkylcarboxylic acids

摘要

Enthalpies of vaporization for esters covering a molecular weight range of about 74-939 g/mol [monocarboxylics; linear esters of sebacic series; branched esters of triglyceride series; and, oligomer esters of poly(hexamethylene sebacate)] and a temperature range of about 273.15-523.15 K have been empirically fitted to within about 5% to an equation of the following form: Delta H upsilon(T,M) = S(T)f(M) + I-O(T), where S(T) = C Ln(T) + K-O, I-O(T) = aT + b(O), and f(M) = M/(1 + a(O)M), M is the molecular weight (molar mass); T is in degrees Kelvin; and, C, K-O, a, b(O), and a(O) are constants. These results were used to determine the heat capacity difference, Delta C-P C-P(I) - C-P(g), and compared to calculated values from functional relationships of C-P(I) and C-P(g), I is liquid g is gas. The heat capacity difference results in conjunction with C-P(I) were used to empirically calculate the heat capacity of the gas, C-P(g), over the molecular weight and temperature ranges investigated and compared to a group contribution method. The functional forms for Delta H upsilon(T,M), Delta C-P(T,M), C-P(l), and C-P(g) were also found to be applicable for n-alkanes. (C) 1998 John Wiley & Sons, Inc. [References: 29]