Crystallization through mesophase in poly(butylene terephthalate): Approach from dependence of growth rate on lamellar thickness

- The T-dependence of spherulitic growth rate was investigated in poly(butylene terephtharate).
- The T-dependence of spherulitic growth rate was compared with that of the lamellar thickness.
- Both of the T-dependences change at 208 °C.
- The crystallization proceeds through the mesophase below 208 °C and directly do above 208 °C.

The temperature dependence of the spherulitic growth rate of poly(butylene terephtharate) (PBT) has been investigated by optical microscopy and compared with the temperature dependence of the lamellar thickness. The changes in the dependence of the growth rate on the lamellar thickness are observed at three temperatures, 218, 208 and 157 °C. The middle temperature, 208 °C, corresponds to the temperature at which the temperature dependence of the lamellar thickness changes. The correspondence leads to the interpretation that the crystalline stem directly forms at the growth front above 208 °C and that the mesomoprhic stem forms below 208 °C.

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