Equation of state for high density solid and melt polyethylene

Pressure‐volume‐temperature (PVT) measurements for high‐density linear polyethylene (LPE) are studied experimentally over a temperature range of 290 to 470 K and pressures up to 3.1 kbar. For melt, the results can be represented by the Tait equation within the precision of the data. It is noticed that for each isotherm, an abrupt departure from the Tait representation occurs at a particular pressure. This is ascribed to onset of solidification due to pressure. Further, variation of the degree of crystallinity with pressure at various temperatures has been investigated. Finally, the PVT data has been analyzed in terms of the LJD cell theory in its original form without any modifications or simplifications of the cell potential. Satisfactory agreement is obtained between experiment and theory over the entire range of PVT data both in solids and melt states. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1618–1623, 2005