The effects on poly(ether ether ketone) (PEEK) of thermal treatment in a particular temperature range in air have been studied. When PEEK is annealed in a partially melted state at a very high temperature, above its original melting point, both crosslinking and crystallization occur. The crosslinking takes place in the melted part in this case, while the crystallization occurs on the surface of the unmelted crystal residues. They lead to the characteristic double-melting peaks of PEEK, representing two distinct crystals. The low-temperature peak arises from the crystals formed during cooling after the treatment, and the higher peak is associated with crystals thickened in the process of annealing. With increasing the annealing time, the low-temperature peak decreases due to the variation in crosslinking of the melted part of PEEK, while the high-temperature peak, which is usually above 350°C, increases and may exceed the equilibrium melting point of PEEK if the annealing time is long enough.
Посилання на статтю:
Effects of thermal treatment on poly(ether ether ketone) / Zhiyi Zhang* and Hanmin Zeng // Polymer. – 1993. – Vol 34. – P. 3648-3652.