Heat Capacity and Thermodynamic Properties of Poly(Vinyl Chloride)

Heat capacities, C , of three different samples of poly(vinyl chloride), PVC, have been determined from 6 to 375 K by adiabatic calorimetry. These three samples were derived from either bulk- or suspension-polymerization processes and were measured either as received or after pelleting under pressure. The heat capacities of the samples are almost identical if the thermal and pressure histories are the same. Below the glass transition temperature, T , of about 355 K, C of PVC was found to be exceptionally linear over a wide temperature range. C of annealed PVC may be represented by (10 + 0.166 T) J K^-1 mol^-1 to within 1 percent of the measured values from 80 to 340 K. Approximately 200 J mol^-1 of energy were stored in the samples by the pelleting processes. The stored energies begin to release at about 30 to 40 K below the glass transition temperature. T for powdery or relaxed samples occurs around 352 to 356 K for the suspension-polymerized PVC sample and 348 to 351 K for bulk-polymerized sample.