Heat capacities of polyethylene from 2 to 360 K. II. Two high density linear polyethylene samples and thermodynamic properties of crystalline linear polyethylene

Heat capaci ties of two high density linear polyethylene sa mples were meas ured from 2 to 360 K. By incorporating th e res ults from the previous work of this serie s, thermodynamic properties of compl e tely crystalline lin ea r polyethylene may be estimated. Cp , H -Ho, Sand -(G -Ho) at 298.15 K for crystalline lin ea r polyethylene are estimated to be 22.60 J K-' mol -I, 3544 J mol -I, 23.02 J K-' mol -' and 3319 J mol -I, respectively. Spo ntaneous adiabatic temperature drifts were obse rved in both sa mpl es near 240 K. These drifts may be attributed to the enthalpy re laxation ph enome na occ urrin g in the glass tran sformation region.