Heat capacity, enthalpy and crystallinity for a linear polyethylene obtained by DSC

By means of computer-controlled DSC, heat-capacity measurements were performed on NBS SRM 1484 betweens-70°C and 250°C, in heating as well as cooling. By using stepwise and continuous measuring methods together with enthalpy calculations, an insight was obtained into the intrinsic consistency and the accuracy of the measurements. The reference states of polyethylene within the two-phase model were used to determine the crystallinity as a function of temperature, and to evaluate various other methods employed for the same purpose.