Crystallinity in chemically crosslinked low-density polyethylene: 5. Annealing behaviour of XLPE-2

The annealing behaviour of lightly crosslinked low-density polyethylenes having various levels of extractable non-crosslinked polyethylene present has been studied. Three separate processes can be identified, which are (a) solid-state annealing, (b) recrystallization and (c) gel-sol separation in the molten state. Unlike linear or linear low-density polyethylene, annealing for long times does not result in crystallization of all crystallizable material; there is always a component present that crystallizes only on cooling if the annealing temperature is in excess of 90°C. The multiple melting peaks observed are not associated with macroscopic morphological features but arise largely from differences in the perfection of crystals or in the character of the amorphous phase in the vicinity of the crystal.