A systematic study using differential scanning calorimetry has been performed on the annealing behaviour of an aromatic polyetherimide (Ultem 5001). Although crystallization from the melt did not occur, crystallinity was easily induced in the presence of methylene chloride. With annealing, a sharp melt endotherm of the solvent-treated polyetherimide was observed. The melt temperature determined after annealing for 30 min increased progressively as the annealing temperature increased, leading to an extrapolation to an apparent equilibrium melt temperature of 369°C. However, the melt temperature, as well as crystallinity, increased with the increase of the residence time at each annealing temperature. X-ray diffraction data revealed two distinct crystalline phases; a low temperature (~) phase obtained by crystallization for 30 min at 248 and 258°C, and a high temperature (fl) phase obtained at 258°C for 3 h or exceeding 258°C. Values of heat of fusion per gram of crystallite were consistent with a range of 247-261 J g-1 for the samples of higher crystallinity
Посилання на статтю:
Transient crystallization of an aromatic polyetherimide: effect of annealing / Alex J. Hsieh, C. Richard Desper and Nathaniel S. Schneider // Polymer. – 1992. – Vol 33. – P. 306-313.