Equilibrium triple point pressure and pressure-temperature phase diagram of polyethylene

The equil. triple point and pressure and temp. phase diagrams of polyethylene were obtained by in situ optical microscopic and x-ray observations of the melting temp. of hexagonal and orthorhombic isolated extended-chain single crystals at high pressure. The melting temps. of extended-chain crystals still showed a DT dependence at high pressure, which has been neglected in previous studies. The triple point pressure and temp. were 0.5 * 108-1.5 * 108 Pa and 20-30 Deg higher than those previously obtained by DTA. Lamellar thickness dependence is important even in extended chain crystals to obtain equil. thermodn. phys. quantities of polymers. [on SciFinder (R)]