The melting behavior and crystn. kinetics of poly(2-hydroxyethoxybenzoate) (PHEBA) were investigated with differential scanning calorimetry and hot-stage optical microscopy. The obsd. multiple endotherms, commonly displayed by polyesters, were influenced by the crystn. temp. By the application of the Hoffman-Weeks method to the melting temps. of isothermally crystd. samples, a value of 232°C was obtained for the equil. melting temp. Isothermal crystn. kinetics were analyzed according to Avrami's treatment. Values of Avrami's exponent n close to 3 were obtained, independently of the crystn. temp., in agreement with a crystn. process originating from predetd. nuclei and characterized by three-dimensional spherulitic growth. In fact, space-filling banded spherulites were obsd. by hot-stage optical microscopy at all crystn. temps. explored, with the band spacing increasing with increasing crystn. temp. The rate of crystn. became lower as the crystn. temp. increased as usual at low undercooling, with the crystn. process controlled by nucleation. The equil. heat of fusion was detd. by differential scanning calorimetry and wide-angle X-ray scattering measurements. Finally, the crystal phase of PHEBA was investigated with wide-angle X-ray scattering, and a triclinic unit cell was hypothesized.
Melting behavior, crystallization kinetics, and crystal structure of poly(2-hydroxyethoxybenzoate)
Gazzano M
2002
Abstract
The melting behavior and crystn. kinetics of poly(2-hydroxyethoxybenzoate) (PHEBA) were investigated with differential scanning calorimetry and hot-stage optical microscopy. The obsd. multiple endotherms, commonly displayed by polyesters, were influenced by the crystn. temp. By the application of the Hoffman-Weeks method to the melting temps. of isothermally crystd. samples, a value of 232°C was obtained for the equil. melting temp. Isothermal crystn. kinetics were analyzed according to Avrami's treatment. Values of Avrami's exponent n close to 3 were obtained, independently of the crystn. temp., in agreement with a crystn. process originating from predetd. nuclei and characterized by three-dimensional spherulitic growth. In fact, space-filling banded spherulites were obsd. by hot-stage optical microscopy at all crystn. temps. explored, with the band spacing increasing with increasing crystn. temp. The rate of crystn. became lower as the crystn. temp. increased as usual at low undercooling, with the crystn. process controlled by nucleation. The equil. heat of fusion was detd. by differential scanning calorimetry and wide-angle X-ray scattering measurements. Finally, the crystal phase of PHEBA was investigated with wide-angle X-ray scattering, and a triclinic unit cell was hypothesized.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
