The pressure–volume–temperature properties of three well-characterized low-density polyethylenes

Pressure–volume–temperature relationships of three low-density polyethylenes are reported in the temperature range of 30°–225°C and in the pressure range of 0–2000 kg/cm2. The same materials had previously been studied by the IUPAC Working Party on Structure and Properties of Commercial Polymers with regard to basic characterization, melt rheology, processing, and end use properties. They were found to be remarkably equal in basic parameters and in some of the melt rheology, but differences among the three samples were found in other rheological properties and in the processing and end use properties of blown film. We find the PVT relationships of these three samples to be practically identical. A numerical equation of state based on the Tait equation is established. It reproduces the measured specific volume data of the melts to better than 0.002 cm3/g.