Specific heat capacities of some polyepoxides

Specific heat capacity measurements were made in a differential scanning calorimeter on a series of eight crosslinked epoxy/diamine polymers over a range of temperatures chosen, for each polymer, to include the glass transition. The tabular data at 5°C intervals was then fitted to a five‐parameter empirical equation that represents the data with a deviation less than the experimental uncertainty of the measurements. The measured change in specific heat at the glass transition was an average of 1.9 cal/mol°C for each bead in the polymer repeat unit compared with 2.6 cal/mol°C bead found by Wunderlich for linear polymers. The measurements were then analyzed in terms of the molecular components of the polymers, assuming that the specific heat contribution of each component is independent of its neighbors, i.e., that specific heat is an additive property. In calculating empirical component values as a function of temperature, the polymer specific heats should be plotted as a function of T – T g rather than T alone. In this manner, component specific heats as functions of T – T g were determined over a range from the glassy to the rubbery state.