Empirical Determination of the Internal Energy of Polyethylene based on the Pressure-Volume-Temperature-Entropy Equation of State

Abstract

The internal energy, U_, of polyethylene (PE) was determined by the relations that $dU=C_{V}dT+\left({\gamma }_{V}T-P\right)dV$ and the pressure-volume-temperature-entropy equation of state (P-V-T-S Eos) evaluated by the experimental P-V-T data and C_p at 1 atm for PE where C_V is the isochoric heat capacity, ${\gamma }_V$ is the thermal pressure coefficient and C_P is the isobaric heat capacity. The 3-dimensional (3D) plot, 3D plot, with the three axes, x = V_U, y = S_U, z = T_U expressed by the 3D (V_U, S_U, T_U), the 3D (T_U, P_U. S_U) or the 3D (T_U, V_U, P_U) at constant U in PE were determined where the four variables, P_U, V_U, T_U, and S_U were determined under U being constant. The P-V-T-S behaviors under the iso-internal energy process where U is constant were monitored by the 3D (V_U, S_U, T_U). The 3D (V, T, P) plot for PE under ${\gamma }_{V}T-P=0\mathrm{ }$ were expressed by a line not a plane$.$

Keywords:

• internal energy
• pressure-volume-temperature-entropy equation of state