Thermodynamic Properties of Polyethylene Predicted from Paraffin Data

Thermodynamic data on the n-paraffins from n-C₆H₁₄ through n-C₁₈H₃₈ have been used to obtain values for the specific heat, entropy, enthalpy, and Gibbs free energy of a large, ideal CH₂-chain crystal from 0 to 420 °K and of the liquid above 200 °K. Analytical expressions are given for the properties of the crystal and liquid above 200 °K. For the crystal, a modified Einstein function was used to adjust the melting temperature to 414.3 °K. Values between 975 and 1025 cal/mole for the heat of fusion were found to be the ones most consistent with the data. Comparison of the results with polyethylene data shows reasonable agreement.