Kinetics of crystallization and melting behaviour of poly(ethylene naphthalene-2,6-dicarboxylate)

The crystallization and melting of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) has been investigated by differential scanning calorimetry and by wide angle X-ray scattering using synchrotron radiation. The material can be crystallized in two different crystal modifications called α and β. At crystallization temperatures up to 200°C only the α-modification is formed. Above this temperature, the β-modification is obtained if the material had been molten at 280°C, while the α-modification is formed if the temperature of the melt was raised to 320°C. The half times of crystallization as a function of temperature show a broad minimum ranging from 180 to 240°C. Under usual conditions, both modifications melt at 272°C. However, by applying a special annealing procedure, the melting points of both modifications can be raised to up to 290°C.